Add AMD SEV guest live migration support

From: Ashish Kalra <[email protected]>

The series add support for AMD SEV guest live migration commands. To protect the confidentiality of an SEV protected guest memory while in transit we need to use the SEV commands defined in SEV API spec [1].

SEV guest VMs have the concept of private and shared memory. Private memory is encrypted with the guest-specific key, while shared memory may be encrypted with hypervisor key. The commands provided by the SEV FW are meant to be used for the private memory only. The patch series introduces a new hypercall. The guest OS can use this hypercall to notify the page encryption status. If the page is encrypted with guest specific-key then we use SEV command during the migration. If page is not encrypted then fallback to default.

The patch uses the KVM_EXIT_HYPERCALL exitcode and hypercall to userspace exit functionality as a common interface from the guest back to the VMM and passing on the guest shared/unencrypted page information to the userspace VMM/Qemu. Qemu can consult this information during migration to know whether the page is encrypted.

This section descibes how the SEV live migration feature is negotiated between the host and guest, the host indicates this feature support via KVM_FEATURE_CPUID. The guest firmware (OVMF) detects this feature and sets a UEFI enviroment variable indicating OVMF support for live migration, the guest kernel also detects the host support for this feature via cpuid and in case of an EFI boot verifies if OVMF also supports this feature by getting the UEFI enviroment variable and if it set then enables live migration feature on host by writing to a custom MSR, if not booted under EFI, then it simply enables the feature by again writing to the custom MSR. The MSR is also handled by the userspace VMM/Qemu.

A branch containing these patches is available here:
https://github.com/AMDESE/linux/tree/sev-migration-v13

[1] https://developer.amd.com/wp-content/resources/55766.PDF

Changes since v12:
- Reset page encryption status during early boot instead of just before the kexec to avoid SMP races during kvm_pv_guest_cpu_reboot().

Quoted 36 lines · Ashish Kalra

From: Ashish Kalra <[email protected]>

The series add support for AMD SEV guest live migration commands. To protect the confidentiality of an SEV protected guest memory while in transit we need to use the SEV commands defined in SEV API spec [1].

SEV guest VMs have the concept of private and shared memory. Private memory is encrypted with the guest-specific key, while shared memory may be encrypted with hypervisor key. The commands provided by the SEV FW are meant to be used for the private memory only. The patch series introduces a new hypercall. The guest OS can use this hypercall to notify the page encryption status. If the page is encrypted with guest specific-key then we use SEV command during the migration. If page is not encrypted then fallback to default.

The patch uses the KVM_EXIT_HYPERCALL exitcode and hypercall to userspace exit functionality as a common interface from the guest back to the VMM and passing on the guest shared/unencrypted page information to the userspace VMM/Qemu. Qemu can consult this information during migration to know whether the page is encrypted.

This section descibes how the SEV live migration feature is negotiated between the host and guest, the host indicates this feature support via KVM_FEATURE_CPUID. The guest firmware (OVMF) detects this feature and sets a UEFI enviroment variable indicating OVMF support for live migration, the guest kernel also detects the host support for this feature via cpuid and in case of an EFI boot verifies if OVMF also supports this feature by getting the UEFI enviroment variable and if it set then enables live migration feature on host by writing to a custom MSR, if not booted under EFI, then it simply enables the feature by again writing to the custom MSR. The MSR is also handled by the userspace VMM/Qemu.

A branch containing these patches is available here:
https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2FAMDESE%2Flinux%2Ftree%2Fsev-migration-v13&amp;data=04%7C01%7CAshish.Kalra%40amd.com%7C7bee6d5c907b46d0998508d90120ce2d%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637542063133830260%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=FkKrciL41GDNyNDqrPMVblRa%2FaReogW4OzhbYaSYs04%3D&amp;reserved=0

Quoted 5 lines

[1] https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdeveloper.amd.com%2Fwp-content%2Fresources%2F55766.PDF&amp;data=04%7C01%7CAshish.Kalra%40amd.com%7C7bee6d5c907b46d0998508d90120ce2d%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637542063133830260%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&amp;sdata=%2FLFBR9ean0acMmR8WTLUHZsAynYPRAa7%2FeZEVVdpCo8%3D&amp;reserved=0

Changes since v12:
- Reset page encryption status during early boot instead of just before the kexec to avoid SMP races during kvm_pv_guest_cpu_reboot().

Does this series need to disable the MSR during kvm_pv_guest_cpu_reboot()?

I _think_ going into blackout during the window after restart, but before the MSR is explicitly reenabled, would cause corruption. The historical shared pages could be re-allocated as non-shared pages during restart.

Steve

From: Ashish Kalra <[email protected]>

Add new KVM_FEATURE_SEV_LIVE_MIGRATION feature for guest to check for host-side support for SEV live migration. Also add a new custom MSR_KVM_SEV_LIVE_MIGRATION for guest to enable the SEV live migration feature.

MSR is handled by userspace using MSR filters.

Signed-off-by Ashish Kalra <[email protected]>

Reviewed-by Steve Rutherford <[email protected]>

---
 Documentation/virt/kvm/cpuid.rst     |  5 +++++
 Documentation/virt/kvm/msr.rst       | 12 ++++++++++++
 arch/x86/include/uapi/asm/kvm_para.h |  4 ++++
 arch/x86/kvm/cpuid.c                 |  3 ++-
 4 files changed, 23 insertions(+), 1 deletion(-)

Documentation/virt/kvm/cpuid.rst +0 -0

index cf62162d4be2..0bdb6cdb12d3 100644

Documentation/virt/kvm/cpuid.rst +0 -0

 KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24          host will warn if no guest-side
                                                per-cpu warps are expected in
                                                kvmclock

Documentation/virt/kvm/msr.rst +12 -0

index e37a14c323d2..020245d16087 100644
@@ -376,3 +376,15 @@ data:
 	write '1' to bit 0 of the MSR, this causes the host to re-scan its queue
 	and check if there are more notifications pending. The MSR is available
 	if KVM_FEATURE_ASYNC_PF_INT is present in CPUID.
+
+MSR_KVM_SEV_LIVE_MIGRATION:
+        0x4b564d08
+
+	Control SEV Live Migration features.
+
+data:
+        Bit 0 enables (1) or disables (0) host-side SEV Live Migration feature,
+        in other words, this is guest->host communication that it's properly
+        handling the shared pages list.
+
+        All other bits are reserved.

arch/x86/include/uapi/asm/kvm_para.h +2 -0

index 950afebfba88..f6bfa138874f 100644
@@ -33,6 +33,7 @@
 #define KVM_FEATURE_PV_SCHED_YIELD	13
 #define KVM_FEATURE_ASYNC_PF_INT	14
 #define KVM_FEATURE_MSI_EXT_DEST_ID	15
+#define KVM_FEATURE_SEV_LIVE_MIGRATION	16
 
 #define KVM_HINTS_REALTIME      0
 

@@ -54,6 +55,7 @@
 #define MSR_KVM_POLL_CONTROL	0x4b564d05
 #define MSR_KVM_ASYNC_PF_INT	0x4b564d06
 #define MSR_KVM_ASYNC_PF_ACK	0x4b564d07
+#define MSR_KVM_SEV_LIVE_MIGRATION	0x4b564d08
 
 struct kvm_steal_time {
 	__u64 steal;

Quoted 3 lines · Ashish Kalra

+    if (!guest_page)
+        goto e_free;
+

Missing unpin on error (but it won't be needed with Sean's patches that move the data block to the stack, so I can fix this too).

From: Brijesh Singh <[email protected]>

The command is used to create an outgoing SEV guest encryption context.

Cc Thomas Gleixner <[email protected]>

Cc Ingo Molnar <[email protected]>

Cc "H. Peter Anvin" <[email protected]>

Cc Paolo Bonzini <[email protected]>

Cc Joerg Roedel <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Tom Lendacky <[email protected]>

Cc [email protected]

Cc [email protected]

Cc [email protected]

Reviewed-by Steve Rutherford <[email protected]>

Reviewed-by Venu Busireddy <[email protected]>

Signed-off-by Brijesh Singh <[email protected]>

Signed-off-by Ashish Kalra <[email protected]>

---
  .../virt/kvm/amd-memory-encryption.rst        |  27 ++++
  arch/x86/kvm/svm/sev.c                        | 125 ++++++++++++++++++
  include/linux/psp-sev.h                       |   8 +-
  include/uapi/linux/kvm.h                      |  12 ++
  4 files changed, 168 insertions(+), 4 deletions(-)

Documentation/virt/kvm/amd-memory-encryption.rst +27 -0

index 469a6308765b..ac799dd7a618 100644
@@ -284,6 +284,33 @@ Returns: 0 on success, -negative on error
                  __u32 len;
          };
 
+10. KVM_SEV_SEND_START
+----------------------
+
+The KVM_SEV_SEND_START command can be used by the hypervisor to create an
+outgoing guest encryption context.
+
+Parameters (in): struct kvm_sev_send_start
+
+Returns: 0 on success, -negative on error
+
+::
+        struct kvm_sev_send_start {
+                __u32 policy;                 /* guest policy */
+
+                __u64 pdh_cert_uaddr;         /* platform Diffie-Hellman certificate */
+                __u32 pdh_cert_len;
+
+                __u64 plat_certs_uaddr;        /* platform certificate chain */
+                __u32 plat_certs_len;
+
+                __u64 amd_certs_uaddr;        /* AMD certificate */
+                __u32 amd_certs_len;
+
+                __u64 session_uaddr;          /* Guest session information */
+                __u32 session_len;
+        };
+
  References
  ==========
 

arch/x86/kvm/svm/sev.c +5 -0

index 874ea309279f..2b65900c05d6 100644
@@ -1110,6 +1110,128 @@ static int sev_get_attestation_report(struct kvm *kvm, struct kvm_sev_cmd *argp)
  	return ret;
  }
 
+/* Userspace wants to query session length. */
+static int
+__sev_send_start_query_session_length(struct kvm *kvm, struct kvm_sev_cmd *argp,
+				      struct kvm_sev_send_start *params)
+{

arch/x86/kvm/svm/sev.c +109 -0

+	params->session_len = data->session_len;
+	if (copy_to_user((void __user *)(uintptr_t)argp->data, params,
+				sizeof(struct kvm_sev_send_start)))
+		ret = -EFAULT;
+
+	kfree(data);
+	return ret;
+}
+
+static int sev_send_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	struct sev_data_send_start *data;
+	struct kvm_sev_send_start params;
+	void *amd_certs, *session_data;
+	void *pdh_cert, *plat_certs;
+	int ret;
+
+	if (!sev_guest(kvm))
+		return -ENOTTY;
+
+	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data,
+				sizeof(struct kvm_sev_send_start)))
+		return -EFAULT;
+
+	/* if session_len is zero, userspace wants to query the session length */
+	if (!params.session_len)
+		return __sev_send_start_query_session_length(kvm, argp,
+				&params);
+
+	/* some sanity checks */
+	if (!params.pdh_cert_uaddr || !params.pdh_cert_len ||
+	    !params.session_uaddr || params.session_len > SEV_FW_BLOB_MAX_SIZE)
+		return -EINVAL;
+
+	/* allocate the memory to hold the session data blob */
+	session_data = kmalloc(params.session_len, GFP_KERNEL_ACCOUNT);
+	if (!session_data)
+		return -ENOMEM;
+
+	/* copy the certificate blobs from userspace */
+	pdh_cert = psp_copy_user_blob(params.pdh_cert_uaddr,
+				params.pdh_cert_len);
+	if (IS_ERR(pdh_cert)) {
+		ret = PTR_ERR(pdh_cert);
+		goto e_free_session;
+	}
+
+	plat_certs = psp_copy_user_blob(params.plat_certs_uaddr,
+				params.plat_certs_len);
+	if (IS_ERR(plat_certs)) {
+		ret = PTR_ERR(plat_certs);
+		goto e_free_pdh;
+	}
+
+	amd_certs = psp_copy_user_blob(params.amd_certs_uaddr,
+				params.amd_certs_len);
+	if (IS_ERR(amd_certs)) {
+		ret = PTR_ERR(amd_certs);
+		goto e_free_plat_cert;
+	}
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
+	if (data == NULL) {
+		ret = -ENOMEM;
+		goto e_free_amd_cert;
+	}
+
+	/* populate the FW SEND_START field with system physical address */
+	data->pdh_cert_address = __psp_pa(pdh_cert);
+	data->pdh_cert_len = params.pdh_cert_len;
+	data->plat_certs_address = __psp_pa(plat_certs);
+	data->plat_certs_len = params.plat_certs_len;
+	data->amd_certs_address = __psp_pa(amd_certs);
+	data->amd_certs_len = params.amd_certs_len;
+	data->session_address = __psp_pa(session_data);
+	data->session_len = params.session_len;
+	data->handle = sev->handle;
+
+	ret = sev_issue_cmd(kvm, SEV_CMD_SEND_START, data, &argp->error);
+
+	if (!ret && copy_to_user((void __user *)(uintptr_t)params.session_uaddr,
+			session_data, params.session_len)) {
+		ret = -EFAULT;
+		goto e_free;
+	}
+
+	params.policy = data->policy;
+	params.session_len = data->session_len;
+	if (copy_to_user((void __user *)(uintptr_t)argp->data, &params,
+				sizeof(struct kvm_sev_send_start)))
+		ret = -EFAULT;
+
+e_free:
+	kfree(data);
+e_free_amd_cert:
+	kfree(amd_certs);
+e_free_plat_cert:
+	kfree(plat_certs);
+e_free_pdh:
+	kfree(pdh_cert);
+e_free_session:
+	kfree(session_data);
+	return ret;
+}
+
  int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
  {
  	struct kvm_sev_cmd sev_cmd;

@@ -1163,6 +1285,9 @@ int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
  	case KVM_SEV_GET_ATTESTATION_REPORT:
  		r = sev_get_attestation_report(kvm, &sev_cmd);
  		break;
+	case KVM_SEV_SEND_START:
+		r = sev_send_start(kvm, &sev_cmd);
+		break;
  	default:
  		r = -EINVAL;
  		goto out;

include/linux/psp-sev.h +4 -4

index b801ead1e2bb..73da511b9423 100644
@@ -326,11 +326,11 @@ struct sev_data_send_start {
  	u64 pdh_cert_address;			/* In */
  	u32 pdh_cert_len;			/* In */
  	u32 reserved1;
-	u64 plat_cert_address;			/* In */
-	u32 plat_cert_len;			/* In */
+	u64 plat_certs_address;			/* In */
+	u32 plat_certs_len;			/* In */
  	u32 reserved2;
-	u64 amd_cert_address;			/* In */
-	u32 amd_cert_len;			/* In */
+	u64 amd_certs_address;			/* In */
+	u32 amd_certs_len;			/* In */
  	u32 reserved3;
  	u64 session_address;			/* In */
  	u32 session_len;			/* In/Out */

include/uapi/linux/kvm.h +12 -0

index f6afee209620..ac53ad2e7271 100644
@@ -1729,6 +1729,18 @@ struct kvm_sev_attestation_report {
  	__u32 len;
  };
 
+struct kvm_sev_send_start {
+	__u32 policy;
+	__u64 pdh_cert_uaddr;
+	__u32 pdh_cert_len;
+	__u64 plat_certs_uaddr;
+	__u32 plat_certs_len;
+	__u64 amd_certs_uaddr;
+	__u32 amd_certs_len;
+	__u64 session_uaddr;
+	__u32 session_len;
+};
+
  #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
  #define KVM_DEV_ASSIGN_PCI_2_3		(1 << 1)
  #define KVM_DEV_ASSIGN_MASK_INTX	(1 << 2)

Quoted 4 lines · Ashish Kalra

+    }
+
+    sev->handle = start->handle;
+    sev->fd = argp->sev_fd;

These two lines are spurious, I'll delete them.

From: Brijesh Singh <[email protected]>

Invoke a hypercall when a memory region is changed from encrypted -> decrypted and vice versa. Hypervisor needs to know the page encryption status during the guest migration.

Cc Thomas Gleixner <[email protected]>

Cc Ingo Molnar <[email protected]>

Cc "H. Peter Anvin" <[email protected]>

Cc Paolo Bonzini <[email protected]>

Cc Joerg Roedel <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Tom Lendacky <[email protected]>

Cc [email protected]

Cc [email protected]

Cc [email protected]

Reviewed-by Steve Rutherford <[email protected]>

Reviewed-by Venu Busireddy <[email protected]>

Signed-off-by Brijesh Singh <[email protected]>

Signed-off-by Ashish Kalra <[email protected]>

---
  arch/x86/include/asm/paravirt.h       | 10 +++++
  arch/x86/include/asm/paravirt_types.h |  2 +
  arch/x86/kernel/paravirt.c            |  1 +
  arch/x86/mm/mem_encrypt.c             | 57 ++++++++++++++++++++++++++-
  arch/x86/mm/pat/set_memory.c          |  7 ++++
  5 files changed, 76 insertions(+), 1 deletion(-)

arch/x86/include/asm/paravirt.h +10 -0

index 4abf110e2243..efaa3e628967 100644
@@ -84,6 +84,12 @@ static inline void paravirt_arch_exit_mmap(struct mm_struct *mm)
  	PVOP_VCALL1(mmu.exit_mmap, mm);
  }
 
+static inline void page_encryption_changed(unsigned long vaddr, int npages,
+						bool enc)
+{
+	PVOP_VCALL3(mmu.page_encryption_changed, vaddr, npages, enc);
+}
+
  #ifdef CONFIG_PARAVIRT_XXL
  static inline void load_sp0(unsigned long sp0)
  {

@@ -799,6 +805,10 @@ static inline void paravirt_arch_dup_mmap(struct mm_struct *oldmm,
  static inline void paravirt_arch_exit_mmap(struct mm_struct *mm)
  {
  }
+
+static inline void page_encryption_changed(unsigned long vaddr, int npages, bool enc)
+{
+}
  #endif
  #endif /* __ASSEMBLY__ */
  #endif /* _ASM_X86_PARAVIRT_H */

arch/x86/include/asm/paravirt_types.h +2 -0

index de87087d3bde..69ef9c207b38 100644
@@ -195,6 +195,8 @@ struct pv_mmu_ops {
 
  	/* Hook for intercepting the destruction of an mm_struct. */
  	void (*exit_mmap)(struct mm_struct *mm);
+	void (*page_encryption_changed)(unsigned long vaddr, int npages,
+					bool enc);
 
  #ifdef CONFIG_PARAVIRT_XXL
  	struct paravirt_callee_save read_cr2;

arch/x86/kernel/paravirt.c +1 -0

index c60222ab8ab9..9f206e192f6b 100644
@@ -335,6 +335,7 @@ struct paravirt_patch_template pv_ops = {
  			(void (*)(struct mmu_gather *, void *))tlb_remove_page,
 
  	.mmu.exit_mmap		= paravirt_nop,
+	.mmu.page_encryption_changed	= paravirt_nop,
 
  #ifdef CONFIG_PARAVIRT_XXL
  	.mmu.read_cr2		= __PV_IS_CALLEE_SAVE(native_read_cr2),

arch/x86/mm/mem_encrypt.c +56 -1

index ae78cef79980..fae9ccbd0da7 100644
@@ -19,6 +19,7 @@
  #include <linux/kernel.h>
  #include <linux/bitops.h>
  #include <linux/dma-mapping.h>
+#include <linux/kvm_para.h>
 
  #include <asm/tlbflush.h>
  #include <asm/fixmap.h>

@@ -29,6 +30,7 @@
  #include <asm/processor-flags.h>
  #include <asm/msr.h>
  #include <asm/cmdline.h>
+#include <asm/kvm_para.h>
 
  #include "mm_internal.h"
 

@@ -229,6 +231,47 @@ void __init sev_setup_arch(void)
  	swiotlb_adjust_size(size);
  }
 
+static void set_memory_enc_dec_hypercall(unsigned long vaddr, int npages,
+					bool enc)
+{
+	unsigned long sz = npages << PAGE_SHIFT;
+	unsigned long vaddr_end, vaddr_next;
+
+	vaddr_end = vaddr + sz;
+
+	for (; vaddr < vaddr_end; vaddr = vaddr_next) {
+		int psize, pmask, level;
+		unsigned long pfn;
+		pte_t *kpte;
+
+		kpte = lookup_address(vaddr, &level);
+		if (!kpte || pte_none(*kpte))
+			return;
+
+		switch (level) {
+		case PG_LEVEL_4K:
+			pfn = pte_pfn(*kpte);
+			break;
+		case PG_LEVEL_2M:
+			pfn = pmd_pfn(*(pmd_t *)kpte);
+			break;
+		case PG_LEVEL_1G:
+			pfn = pud_pfn(*(pud_t *)kpte);
+			break;
+		default:
+			return;
+		}
+
+		psize = page_level_size(level);
+		pmask = page_level_mask(level);
+
+		kvm_sev_hypercall3(KVM_HC_PAGE_ENC_STATUS,
+				   pfn << PAGE_SHIFT, psize >> PAGE_SHIFT, enc);
+
+		vaddr_next = (vaddr & pmask) + psize;
+	}
+}
+
  static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
  {
  	pgprot_t old_prot, new_prot;

@@ -286,12 +329,13 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
  static int __init early_set_memory_enc_dec(unsigned long vaddr,
  					   unsigned long size, bool enc)
  {
-	unsigned long vaddr_end, vaddr_next;
+	unsigned long vaddr_end, vaddr_next, start;
  	unsigned long psize, pmask;
  	int split_page_size_mask;
  	int level, ret;
  	pte_t *kpte;
 
+	start = vaddr;
  	vaddr_next = vaddr;
  	vaddr_end = vaddr + size;
 

@@ -346,6 +390,8 @@ static int __init early_set_memory_enc_dec(unsigned long vaddr,
 
  	ret = 0;
 
+	set_memory_enc_dec_hypercall(start, PAGE_ALIGN(size) >> PAGE_SHIFT,
+					enc);
  out:
  	__flush_tlb_all();
  	return ret;

@@ -481,6 +527,15 @@ void __init mem_encrypt_init(void)
  	if (sev_active() && !sev_es_active())
  		static_branch_enable(&sev_enable_key);
 
+#ifdef CONFIG_PARAVIRT
+	/*
+	 * With SEV, we need to make a hypercall when page encryption state is
+	 * changed.
+	 */
+	if (sev_active())
+		pv_ops.mmu.page_encryption_changed = set_memory_enc_dec_hypercall;
+#endif
+
  	print_mem_encrypt_feature_info();
  }
 

arch/x86/mm/pat/set_memory.c +7 -0

index 16f878c26667..3576b583ac65 100644
@@ -27,6 +27,7 @@
  #include <asm/proto.h>
  #include <asm/memtype.h>
  #include <asm/set_memory.h>
+#include <asm/paravirt.h>
 
  #include "../mm_internal.h"
 

@@ -2012,6 +2013,12 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
  	 */
  	cpa_flush(&cpa, 0);
 
+	/* Notify hypervisor that a given memory range is mapped encrypted
+	 * or decrypted. The hypervisor will use this information during the
+	 * VM migration.
+	 */
+	page_encryption_changed(addr, numpages, enc);
+
  	return ret;
  }
 

From: Ashish Kalra <[email protected]>

Add new KVM_FEATURE_SEV_LIVE_MIGRATION feature for guest to check for host-side support for SEV live migration. Also add a new custom MSR_KVM_SEV_LIVE_MIGRATION for guest to enable the SEV live migration feature.

MSR is handled by userspace using MSR filters.

Signed-off-by Ashish Kalra <[email protected]>

Reviewed-by Steve Rutherford <[email protected]>

---
  Documentation/virt/kvm/cpuid.rst     |  5 +++++
  Documentation/virt/kvm/msr.rst       | 12 ++++++++++++
  arch/x86/include/uapi/asm/kvm_para.h |  4 ++++
  arch/x86/kvm/cpuid.c                 |  3 ++-
  4 files changed, 23 insertions(+), 1 deletion(-)

Documentation/virt/kvm/cpuid.rst +5 -0

index cf62162d4be2..0bdb6cdb12d3 100644
@@ -96,6 +96,11 @@ KVM_FEATURE_MSI_EXT_DEST_ID        15          guest checks this feature bit
                                                 before using extended destination
                                                 ID bits in MSI address bits 11-5.
 
+KVM_FEATURE_SEV_LIVE_MIGRATION     16          guest checks this feature bit before
+                                               using the page encryption state
+                                               hypercall to notify the page state
+                                               change
+
  KVM_FEATURE_CLOCKSOURCE_STABLE_BIT 24          host will warn if no guest-side
                                                 per-cpu warps are expected in
                                                 kvmclock

Documentation/virt/kvm/msr.rst +12 -0

index e37a14c323d2..020245d16087 100644
@@ -376,3 +376,15 @@ data:
  	write '1' to bit 0 of the MSR, this causes the host to re-scan its queue
  	and check if there are more notifications pending. The MSR is available
  	if KVM_FEATURE_ASYNC_PF_INT is present in CPUID.
+
+MSR_KVM_SEV_LIVE_MIGRATION:
+        0x4b564d08
+
+	Control SEV Live Migration features.
+
+data:
+        Bit 0 enables (1) or disables (0) host-side SEV Live Migration feature,
+        in other words, this is guest->host communication that it's properly
+        handling the shared pages list.
+
+        All other bits are reserved.

arch/x86/include/uapi/asm/kvm_para.h +4 -0

index 950afebfba88..f6bfa138874f 100644
@@ -33,6 +33,7 @@
  #define KVM_FEATURE_PV_SCHED_YIELD	13
  #define KVM_FEATURE_ASYNC_PF_INT	14
  #define KVM_FEATURE_MSI_EXT_DEST_ID	15
+#define KVM_FEATURE_SEV_LIVE_MIGRATION	16
 
  #define KVM_HINTS_REALTIME      0
 

@@ -54,6 +55,7 @@
  #define MSR_KVM_POLL_CONTROL	0x4b564d05
  #define MSR_KVM_ASYNC_PF_INT	0x4b564d06
  #define MSR_KVM_ASYNC_PF_ACK	0x4b564d07
+#define MSR_KVM_SEV_LIVE_MIGRATION	0x4b564d08
 
  struct kvm_steal_time {
  	__u64 steal;

@@ -136,4 +138,6 @@ struct kvm_vcpu_pv_apf_data {
  #define KVM_PV_EOI_ENABLED KVM_PV_EOI_MASK
  #define KVM_PV_EOI_DISABLED 0x0
 
+#define KVM_SEV_LIVE_MIGRATION_ENABLED BIT_ULL(0)
+
  #endif /* _UAPI_ASM_X86_KVM_PARA_H */

arch/x86/kvm/cpuid.c +2 -1

index 6bd2f8b830e4..4e2e69a692aa 100644
@@ -812,7 +812,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
  			     (1 << KVM_FEATURE_PV_SEND_IPI) |
  			     (1 << KVM_FEATURE_POLL_CONTROL) |
  			     (1 << KVM_FEATURE_PV_SCHED_YIELD) |
-			     (1 << KVM_FEATURE_ASYNC_PF_INT);
+			     (1 << KVM_FEATURE_ASYNC_PF_INT) |
+			     (1 << KVM_FEATURE_SEV_LIVE_MIGRATION);
 
  		if (sched_info_on())
  			entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);

Quoted 24 lines

arch/x86/include/uapi/asm/kvm_para.h +2 -0

index 950afebfba88..f6bfa138874f 100644
@@ -33,6 +33,7 @@
  #define KVM_FEATURE_PV_SCHED_YIELD	13
  #define KVM_FEATURE_ASYNC_PF_INT	14
  #define KVM_FEATURE_MSI_EXT_DEST_ID	15
+#define KVM_FEATURE_SEV_LIVE_MIGRATION	16
 
  #define KVM_HINTS_REALTIME      0
 

@@ -54,6 +55,7 @@
  #define MSR_KVM_POLL_CONTROL	0x4b564d05
  #define MSR_KVM_ASYNC_PF_INT	0x4b564d06
  #define MSR_KVM_ASYNC_PF_ACK	0x4b564d07
+#define MSR_KVM_SEV_LIVE_MIGRATION	0x4b564d08
 
  struct kvm_steal_time {
  	__u64 steal;

@@ -136,4 +138,6 @@ struct kvm_vcpu_pv_apf_data {
  #define KVM_PV_EOI_ENABLED KVM_PV_EOI_MASK
  #define KVM_PV_EOI_DISABLED 0x0
 

arch/x86/include/uapi/asm/kvm_para.h struct kvm_vcpu_pv_apf_data { · line 141

Quoted 1 line

arch/x86/include/uapi/asm/kvm_para.h +1 -0

+#define KVM_SEV_LIVE_MIGRATION_ENABLED BIT_ULL(0)

Even though the intent is to "force" userspace to intercept the MSR, I think KVM should at least emulate the legal bits as a nop. Deferring completely to userspace is rather bizarre as there's not really anything to justify KVM getting involved. It would also force userspace to filter the MSR just to support the hypercall.

Somewhat of a nit, but I think we should do something like s/ENABLED/READY,

From: Ashish Kalra <[email protected]>

The guest support for detecting and enabling SEV Live migration feature uses the following logic :

- kvm_init_plaform() invokes check_kvm_sev_migration() which checks if its booted under the EFI

- If not EFI,

i) check for the KVM_FEATURE_CPUID

ii) if CPUID reports that migration is supported, issue a wrmsrl()
to enable the SEV live migration support

- If EFI,

i) check for the KVM_FEATURE_CPUID

ii) If CPUID reports that migration is supported, read the UEFI variable which
indicates OVMF support for live migration

iii) the variable indicates live migration is supported, issue a wrmsrl() to
enable the SEV live migration support

The EFI live migration check is done using a late_initcall() callback.

Also, ensure that _bss_decrypted section is marked as decrypted in the shared pages list.

Also adds kexec support for SEV Live Migration.

Reset the host's shared pages list related to kernel specific page encryption status settings before we load a new kernel by kexec. We cannot reset the complete shared pages list here as we need to retain the UEFI/OVMF firmware specific settings.

The host's shared pages list is maintained for the guest to keep track of all unencrypted guest memory regions, therefore we need to explicitly mark all shared pages as encrypted again before rebooting into the new guest kernel.

Signed-off-by Ashish Kalra <[email protected]>

---
  arch/x86/include/asm/mem_encrypt.h |  8 ++++
  arch/x86/kernel/kvm.c              | 55 +++++++++++++++++++++++++
  arch/x86/mm/mem_encrypt.c          | 64 ++++++++++++++++++++++++++++++
  3 files changed, 127 insertions(+)

arch/x86/include/asm/mem_encrypt.h +8 -0

index 31c4df123aa0..19b77f3a62dc 100644
@@ -21,6 +21,7 @@
  extern u64 sme_me_mask;
  extern u64 sev_status;
  extern bool sev_enabled;
+extern bool sev_live_migration_enabled;
 
  void sme_encrypt_execute(unsigned long encrypted_kernel_vaddr,
  			 unsigned long decrypted_kernel_vaddr,

@@ -44,8 +45,11 @@ void __init sme_enable(struct boot_params *bp);
 
  int __init early_set_memory_decrypted(unsigned long vaddr, unsigned long size);
  int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size);
+void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages,
+					    bool enc);
 
  void __init mem_encrypt_free_decrypted_mem(void);
+void __init check_kvm_sev_migration(void);
 
  /* Architecture __weak replacement functions */
  void __init mem_encrypt_init(void);

@@ -60,6 +64,7 @@ bool sev_es_active(void);
  #else	/* !CONFIG_AMD_MEM_ENCRYPT */
 
  #define sme_me_mask	0ULL
+#define sev_live_migration_enabled	false
 
  static inline void __init sme_early_encrypt(resource_size_t paddr,
  					    unsigned long size) { }

@@ -84,8 +89,11 @@ static inline int __init
  early_set_memory_decrypted(unsigned long vaddr, unsigned long size) { return 0; }
  static inline int __init
  early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; }
+static inline void __init
+early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages, bool enc) {}
 
  static inline void mem_encrypt_free_decrypted_mem(void) { }
+static inline void check_kvm_sev_migration(void) { }
 
  #define __bss_decrypted
 

arch/x86/kernel/kvm.c +55 -0

index 78bb0fae3982..94ef16d263a7 100644
@@ -26,6 +26,7 @@
  #include <linux/kprobes.h>
  #include <linux/nmi.h>
  #include <linux/swait.h>
+#include <linux/efi.h>
  #include <asm/timer.h>
  #include <asm/cpu.h>
  #include <asm/traps.h>

@@ -429,6 +430,59 @@ static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
  	early_set_memory_decrypted((unsigned long) ptr, size);
  }
 
+static int __init setup_kvm_sev_migration(void)
+{
+	efi_char16_t efi_sev_live_migration_enabled[] = L"SevLiveMigrationEnabled";
+	efi_guid_t efi_variable_guid = MEM_ENCRYPT_GUID;
+	efi_status_t status;
+	unsigned long size;
+	bool enabled;
+
+	/*
+	 * check_kvm_sev_migration() invoked via kvm_init_platform() before
+	 * this callback would have setup the indicator that live migration
+	 * feature is supported/enabled.
+	 */
+	if (!sev_live_migration_enabled)
+		return 0;
+
+	if (!efi_enabled(EFI_BOOT))
+		return 0;
+
+	if (!efi_enabled(EFI_RUNTIME_SERVICES)) {
+		pr_info("%s : EFI runtime services are not enabled\n", __func__);
+		return 0;
+	}
+
+	size = sizeof(enabled);
+
+	/* Get variable contents into buffer */
+	status = efi.get_variable(efi_sev_live_migration_enabled,
+				  &efi_variable_guid, NULL, &size, &enabled);
+
+	if (status == EFI_NOT_FOUND) {
+		pr_info("%s : EFI live migration variable not found\n", __func__);
+		return 0;
+	}
+
+	if (status != EFI_SUCCESS) {
+		pr_info("%s : EFI variable retrieval failed\n", __func__);
+		return 0;
+	}
+
+	if (enabled == 0) {
+		pr_info("%s: live migration disabled in EFI\n", __func__);
+		return 0;
+	}
+
+	pr_info("%s : live migration enabled in EFI\n", __func__);
+	wrmsrl(MSR_KVM_SEV_LIVE_MIGRATION, KVM_SEV_LIVE_MIGRATION_ENABLED);
+
+	return true;
+}
+
+late_initcall(setup_kvm_sev_migration);
+
  /*
   * Iterate through all possible CPUs and map the memory region pointed
   * by apf_reason, steal_time and kvm_apic_eoi as decrypted at once.

@@ -747,6 +801,7 @@ static bool __init kvm_msi_ext_dest_id(void)
 
  static void __init kvm_init_platform(void)
  {
+	check_kvm_sev_migration();
  	kvmclock_init();
  	x86_platform.apic_post_init = kvm_apic_init;
  }

arch/x86/mm/mem_encrypt.c +64 -0

index fae9ccbd0da7..382d1d4f00f5 100644
@@ -20,6 +20,7 @@
  #include <linux/bitops.h>
  #include <linux/dma-mapping.h>
  #include <linux/kvm_para.h>
+#include <linux/efi.h>
 
  #include <asm/tlbflush.h>
  #include <asm/fixmap.h>

@@ -31,6 +32,7 @@
  #include <asm/msr.h>
  #include <asm/cmdline.h>
  #include <asm/kvm_para.h>
+#include <asm/e820/api.h>
 
  #include "mm_internal.h"
 

@@ -48,6 +50,8 @@ EXPORT_SYMBOL_GPL(sev_enable_key);
 
  bool sev_enabled __section(".data");
 
+bool sev_live_migration_enabled __section(".data");
+
  /* Buffer used for early in-place encryption by BSP, no locking needed */
  static char sme_early_buffer[PAGE_SIZE] __initdata __aligned(PAGE_SIZE);
 

@@ -237,6 +241,9 @@ static void set_memory_enc_dec_hypercall(unsigned long vaddr, int npages,
  	unsigned long sz = npages << PAGE_SHIFT;
  	unsigned long vaddr_end, vaddr_next;
 
+	if (!sev_live_migration_enabled)
+		return;
+
  	vaddr_end = vaddr + sz;
 
  	for (; vaddr < vaddr_end; vaddr = vaddr_next) {

@@ -407,6 +414,12 @@ int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size)
  	return early_set_memory_enc_dec(vaddr, size, true);
  }
 
+void __init early_set_mem_enc_dec_hypercall(unsigned long vaddr, int npages,
+					bool enc)
+{
+	set_memory_enc_dec_hypercall(vaddr, npages, enc);
+}
+
  /*
   * SME and SEV are very similar but they are not the same, so there are
   * times that the kernel will need to distinguish between SME and SEV. The

@@ -462,6 +475,57 @@ bool force_dma_unencrypted(struct device *dev)
  	return false;
  }
 
+void __init check_kvm_sev_migration(void)
+{
+	if (sev_active() &&
+	    kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)) {
+		unsigned long nr_pages;
+		int i;
+
+		pr_info("KVM enable live migration\n");
+		WRITE_ONCE(sev_live_migration_enabled, true);
+
+		/*
+		 * Reset the host's shared pages list related to kernel
+		 * specific page encryption status settings before we load a
+		 * new kernel by kexec. Reset the page encryption status
+		 * during early boot intead of just before kexec to avoid SMP
+		 * races during kvm_pv_guest_cpu_reboot().
+		 * NOTE: We cannot reset the complete shared pages list
+		 * here as we need to retain the UEFI/OVMF firmware
+		 * specific settings.
+		 */
+
+		for (i = 0; i < e820_table->nr_entries; i++) {
+			struct e820_entry *entry = &e820_table->entries[i];
+
+			if (entry->type != E820_TYPE_RAM)
+				continue;
+
+			nr_pages = DIV_ROUND_UP(entry->size, PAGE_SIZE);
+
+			kvm_sev_hypercall3(KVM_HC_PAGE_ENC_STATUS, entry->addr,
+					   nr_pages, 1);
+		}
+
+		/*
+		 * Ensure that _bss_decrypted section is marked as decrypted in the
+		 * shared pages list.
+		 */
+		nr_pages = DIV_ROUND_UP(__end_bss_decrypted - __start_bss_decrypted,
+					PAGE_SIZE);
+		early_set_mem_enc_dec_hypercall((unsigned long)__start_bss_decrypted,
+						nr_pages, 0);
+
+		/*
+		 * If not booted using EFI, enable Live migration support.
+		 */
+		if (!efi_enabled(EFI_BOOT))
+			wrmsrl(MSR_KVM_SEV_LIVE_MIGRATION,
+			       KVM_SEV_LIVE_MIGRATION_ENABLED);
+	}
+}
+
  void __init mem_encrypt_free_decrypted_mem(void)
  {
  	unsigned long vaddr, vaddr_end, npages;

From: Ashish Kalra <[email protected]>

This hypercall is used by the SEV guest to notify a change in the page encryption status to the hypervisor. The hypercall should be invoked only when the encryption attribute is changed from encrypted -> decrypted and vice versa. By default all guest pages are considered encrypted.

The hypercall exits to userspace to manage the guest shared regions and integrate with the userspace VMM's migration code.

Cc Thomas Gleixner <[email protected]>

Cc Ingo Molnar <[email protected]>

Cc "H. Peter Anvin" <[email protected]>

Cc Paolo Bonzini <[email protected]>

Cc Joerg Roedel <[email protected]>

Cc Borislav Petkov <[email protected]>

Cc Tom Lendacky <[email protected]>

Cc [email protected]

Cc [email protected]

Cc [email protected]

Reviewed-by Steve Rutherford <[email protected]>

Signed-off-by Brijesh Singh <[email protected]>

Signed-off-by Ashish Kalra <[email protected]>

Co-developed-by Sean Christopherson <[email protected]>

Signed-off-by Sean Christopherson <[email protected]>

---
  Documentation/virt/kvm/hypercalls.rst | 15 ++++++++++++++
  arch/x86/include/asm/kvm_host.h       |  2 ++
  arch/x86/kvm/svm/sev.c                |  1 +
  arch/x86/kvm/x86.c                    | 29 +++++++++++++++++++++++++++
  include/uapi/linux/kvm_para.h         |  1 +
  5 files changed, 48 insertions(+)

Documentation/virt/kvm/hypercalls.rst +15 -0

index ed4fddd364ea..7aff0cebab7c 100644
@@ -169,3 +169,18 @@ a0: destination APIC ID
 
  :Usage example: When sending a call-function IPI-many to vCPUs, yield if
  	        any of the IPI target vCPUs was preempted.
+
+
+8. KVM_HC_PAGE_ENC_STATUS
+-------------------------
+:Architecture: x86
+:Status: active
+:Purpose: Notify the encryption status changes in guest page table (SEV guest)
+
+a0: the guest physical address of the start page
+a1: the number of pages
+a2: encryption attribute
+
+   Where:
+	* 1: Encryption attribute is set
+	* 0: Encryption attribute is cleared

arch/x86/include/asm/kvm_host.h +2 -0

index 3768819693e5..42eb0fe3df5d 100644
@@ -1050,6 +1050,8 @@ struct kvm_arch {
 
  	bool bus_lock_detection_enabled;
 
+	bool page_enc_hc_enable;
+
  	/* Deflect RDMSR and WRMSR to user space when they trigger a #GP */
  	u32 user_space_msr_mask;
  	struct kvm_x86_msr_filter __rcu *msr_filter;

arch/x86/kvm/svm/sev.c +1 -0

index c9795a22e502..5184a0c0131a 100644
@@ -197,6 +197,7 @@ static int sev_guest_init(struct kvm *kvm, struct kvm_sev_cmd *argp)
  	sev->active = true;
  	sev->asid = asid;
  	INIT_LIST_HEAD(&sev->regions_list);
+	kvm->arch.page_enc_hc_enable = true;
 
  	return 0;
 

arch/x86/kvm/x86.c +29 -0

index f7d12fca397b..e8986478b653 100644
@@ -8208,6 +8208,13 @@ static void kvm_sched_yield(struct kvm *kvm, unsigned long dest_id)
  		kvm_vcpu_yield_to(target);
  }
 
+static int complete_hypercall_exit(struct kvm_vcpu *vcpu)
+{
+	kvm_rax_write(vcpu, vcpu->run->hypercall.ret);
+	++vcpu->stat.hypercalls;
+	return kvm_skip_emulated_instruction(vcpu);
+}
+
  int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
  {
  	unsigned long nr, a0, a1, a2, a3, ret;

@@ -8273,6 +8280,28 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu)
  		kvm_sched_yield(vcpu->kvm, a0);
  		ret = 0;
  		break;
+	case KVM_HC_PAGE_ENC_STATUS: {
+		u64 gpa = a0, npages = a1, enc = a2;
+
+		ret = -KVM_ENOSYS;
+		if (!vcpu->kvm->arch.page_enc_hc_enable)
+			break;
+
+		if (!PAGE_ALIGNED(gpa) || !npages ||
+		    gpa_to_gfn(gpa) + npages <= gpa_to_gfn(gpa)) {
+			ret = -EINVAL;
+			break;
+		}
+
+		vcpu->run->exit_reason        = KVM_EXIT_HYPERCALL;
+		vcpu->run->hypercall.nr       = KVM_HC_PAGE_ENC_STATUS;
+		vcpu->run->hypercall.args[0]  = gpa;
+		vcpu->run->hypercall.args[1]  = npages;
+		vcpu->run->hypercall.args[2]  = enc;
+		vcpu->run->hypercall.longmode = op_64_bit;
+		vcpu->arch.complete_userspace_io = complete_hypercall_exit;
+		return 0;
+	}
  	default:
  		ret = -KVM_ENOSYS;
  		break;

include/uapi/linux/kvm_para.h +1 -0

index 8b86609849b9..847b83b75dc8 100644
@@ -29,6 +29,7 @@
  #define KVM_HC_CLOCK_PAIRING		9
  #define KVM_HC_SEND_IPI		10
  #define KVM_HC_SCHED_YIELD		11
+#define KVM_HC_PAGE_ENC_STATUS		12
 
  /*
   * hypercalls use architecture specific

From: Ashish Kalra <[email protected]>

The series add support for AMD SEV guest live migration commands. To protect the confidentiality of an SEV protected guest memory while in transit we need to use the SEV commands defined in SEV API spec [1].

SEV guest VMs have the concept of private and shared memory. Private memory is encrypted with the guest-specific key, while shared memory may be encrypted with hypervisor key. The commands provided by the SEV FW are meant to be used for the private memory only. The patch series introduces a new hypercall. The guest OS can use this hypercall to notify the page encryption status. If the page is encrypted with guest specific-key then we use SEV command during the migration. If page is not encrypted then fallback to default.

The patch uses the KVM_EXIT_HYPERCALL exitcode and hypercall to userspace exit functionality as a common interface from the guest back to the VMM and passing on the guest shared/unencrypted page information to the userspace VMM/Qemu. Qemu can consult this information during migration to know whether the page is encrypted.

This section descibes how the SEV live migration feature is negotiated between the host and guest, the host indicates this feature support via KVM_FEATURE_CPUID. The guest firmware (OVMF) detects this feature and sets a UEFI enviroment variable indicating OVMF support for live migration, the guest kernel also detects the host support for this feature via cpuid and in case of an EFI boot verifies if OVMF also supports this feature by getting the UEFI enviroment variable and if it set then enables live migration feature on host by writing to a custom MSR, if not booted under EFI, then it simply enables the feature by again writing to the custom MSR. The MSR is also handled by the userspace VMM/Qemu.

A branch containing these patches is available here:
https://github.com/AMDESE/linux/tree/sev-migration-v13

[1] https://developer.amd.com/wp-content/resources/55766.PDF

Changes since v12:
- Reset page encryption status during early boot instead of just before the kexec to avoid SMP races during kvm_pv_guest_cpu_reboot().
- Remove incorrect log message in case of non-EFI boot and implicit enabling of SEV live migration feature.

Changes since v11:
- Clean up and remove kvm_x86_ops callback for page_enc_status_hc and instead add a new per-VM flag to support/enable the page encryption status hypercall.
- Remove KVM_EXIT_DMA_SHARE/KVM_EXIT_DMA_UNSHARE exitcodes and instead use the KVM_EXIT_HYPERCALL exitcode for page encryption status hypercall to userspace functionality.

Changes since v10:
- Adds new KVM_EXIT_DMA_SHARE/KVM_EXIT_DMA_UNSHARE hypercall to userspace exit functionality as a common interface from the guest back to the KVM and passing on the guest shared/unencrypted region information to the userspace VMM/Qemu. KVM/host kernel does not maintain the guest shared memory regions information anymore.
- Remove implicit enabling of SEV live migration feature for an SEV guest, now this is explicitly in control of the userspace VMM/Qemu.
- Custom MSR handling is also now moved into userspace VMM/Qemu.
- As KVM does not maintain the guest shared memory region information anymore, sev_dbg_crypt() cannot bypass unencrypted guest memory regions without support from userspace VMM/Qemu.

Changes since v9:
- Transitioning from page encryption bitmap to the shared pages list to keep track of guest's shared/unencrypted memory regions.
- Move back to marking the complete _bss_decrypted section as decrypted in the shared pages list.
- Invoke a new function check_kvm_sev_migration() via kvm_init_platform() for guest to query for host-side support for SEV live migration and to enable the SEV live migration feature, to avoid #ifdefs in code
- Rename MSR_KVM_SEV_LIVE_MIG_EN to MSR_KVM_SEV_LIVE_MIGRATION.
- Invoke a new function handle_unencrypted_region() from sev_dbg_crypt() to bypass unencrypted guest memory regions.

Changes since v8:
- Rebasing to kvm next branch.
- Fixed and added comments as per review feedback on v8 patches.
- Removed implicitly enabling live migration for incoming VMs in in KVM_SET_PAGE_ENC_BITMAP, it is now done via KVM_SET_MSR ioctl.
- Adds support for bypassing unencrypted guest memory regions for DBG_DECRYPT API calls, guest memory region encryption status in sev_dbg_decrypt() is referenced using the page encryption bitmap.

Changes since v7:
- Removed the hypervisor specific hypercall/paravirt callback for SEV live migration and moved back to calling kvm_sev_hypercall3 directly.
- Fix build errors as

Reported-by kbuild test robot <[email protected]>, specifically fixed

build error when CONFIG_HYPERVISOR_GUEST=y and CONFIG_AMD_MEM_ENCRYPT=n.
- Implicitly enabled live migration for incoming VM(s) to handle A->B->C->... VM migrations.
- Fixed Documentation as per comments on v6 patches.
- Fixed error return path in sev_send_update_data() as per comments on v6 patches.

Changes since v6:
- Rebasing to mainline and refactoring to the new split SVM infrastructre.
- Move to static allocation of the unified Page Encryption bitmap instead of the dynamic resizing of the bitmap, the static allocation is done implicitly by extending kvm_arch_commit_memory_region() callack to add svm specific x86_ops which can read the userspace provided memory region/memslots and calculate the amount of guest RAM managed by the KVM and grow the bitmap.
- Fixed KVM_SET_PAGE_ENC_BITMAP ioctl to set the whole bitmap instead of simply clearing specific bits.
- Removed KVM_PAGE_ENC_BITMAP_RESET ioctl, which is now performed using KVM_SET_PAGE_ENC_BITMAP.
- Extended guest support for enabling Live Migration feature by adding a check for UEFI environment variable indicating OVMF support for Live Migration feature and additionally checking for KVM capability for the same feature. If not booted under EFI, then we simply check for KVM capability.
- Add hypervisor specific hypercall for SEV live migration by adding a new paravirt callback as part of x86_hyper_runtime.
(x86 hypervisor specific runtime callbacks)
- Moving MSR handling for MSR_KVM_SEV_LIVE_MIG_EN into svm/sev code and adding check for SEV live migration enabled by guest in the KVM_GET_PAGE_ENC_BITMAP ioctl.
- Instead of the complete __bss_decrypted section, only specific variables such as hv_clock_boot and wall_clock are marked as decrypted in the page encryption bitmap

Changes since v5:
- Fix build errors as

Reported-by kbuild test robot <[email protected]>

Changes since v4:
- Host support has been added to extend KVM capabilities/feature bits to include a new KVM_FEATURE_SEV_LIVE_MIGRATION, which the guest can query for host-side support for SEV live migration and a new custom MSR MSR_KVM_SEV_LIVE_MIG_EN is added for guest to enable the SEV live migration feature.
- Ensure that _bss_decrypted section is marked as decrypted in the page encryption bitmap.
- Fixing KVM_GET_PAGE_ENC_BITMAP ioctl to return the correct bitmap as per the number of pages being requested by the user. Ensure that we only copy bmap->num_pages bytes in the userspace buffer, if bmap->num_pages is not byte aligned we read the trailing bits from the userspace and copy those bits as is. This fixes guest page(s) corruption issues observed after migration completion.
- Add kexec support for SEV Live Migration to reset the host's page encryption bitmap related to kernel specific page encryption status settings before we load a new kernel by kexec. We cannot reset the complete page encryption bitmap here as we need to retain the UEFI/OVMF firmware specific settings.

Changes since v3:
- Rebasing to mainline and testing.
- Adding a new KVM_PAGE_ENC_BITMAP_RESET ioctl, which resets the page encryption bitmap on a guest reboot event.
- Adding a more reliable sanity check for GPA range being passed to the hypercall to ensure that guest MMIO ranges are also marked in the page encryption bitmap.

Changes since v2:
- reset the page encryption bitmap on vcpu reboot

Changes since v1:
- Add support to share the page encryption between the source and target machine.
- Fix review feedbacks from Tom Lendacky.
- Add check to limit the session blob length.
- Update KVM_GET_PAGE_ENC_BITMAP icotl to use the base_gfn instead of the memory slot when querying the bitmap.

Ashish Kalra (4):
KVM: X86: Introduce KVM_HC_PAGE_ENC_STATUS hypercall
KVM: x86: Introduce new KVM_FEATURE_SEV_LIVE_MIGRATION feature &
Custom MSR.
EFI: Introduce the new AMD Memory Encryption GUID. x86/kvm: Add guest support for detecting and enabling SEV Live
Migration feature.

Brijesh Singh (8):
KVM: SVM: Add KVM_SEV SEND_START command
KVM: SVM: Add KVM_SEND_UPDATE_DATA command
KVM: SVM: Add KVM_SEV_SEND_FINISH command
KVM: SVM: Add support for KVM_SEV_RECEIVE_START command
KVM: SVM: Add KVM_SEV_RECEIVE_UPDATE_DATA command
KVM: SVM: Add KVM_SEV_RECEIVE_FINISH command
KVM: x86: Add AMD SEV specific Hypercall3
mm: x86: Invoke hypercall when page encryption status is changed

  .../virt/kvm/amd-memory-encryption.rst        | 120 +++++
  Documentation/virt/kvm/cpuid.rst              |   5 +
  Documentation/virt/kvm/hypercalls.rst         |  15 +
  Documentation/virt/kvm/msr.rst                |  12 +
  arch/x86/include/asm/kvm_host.h               |   2 +
  arch/x86/include/asm/kvm_para.h               |  12 +
  arch/x86/include/asm/mem_encrypt.h            |   8 +
  arch/x86/include/asm/paravirt.h               |  10 +
  arch/x86/include/asm/paravirt_types.h         |   2 +
  arch/x86/include/uapi/asm/kvm_para.h          |   4 +
  arch/x86/kernel/kvm.c                         |  55 +++
  arch/x86/kernel/paravirt.c                    |   1 +
  arch/x86/kvm/cpuid.c                          |   3 +-
  arch/x86/kvm/svm/sev.c                        | 454 ++++++++++++++++++
  arch/x86/kvm/x86.c                            |  29 ++
  arch/x86/mm/mem_encrypt.c                     | 121 ++++-
  arch/x86/mm/pat/set_memory.c                  |   7 +
  include/linux/efi.h                           |   1 +
  include/linux/psp-sev.h                       |   8 +-
  include/uapi/linux/kvm.h                      |  39 ++
  include/uapi/linux/kvm_para.h                 |   1 +
  21 files changed, 903 insertions(+), 6 deletions(-)

Quoted 9 lines · Ashish Kalra

From: Ashish Kalra <[email protected]>

This hypercall is used by the SEV guest to notify a change in the page encryption status to the hypervisor. The hypercall should be invoked only when the encryption attribute is changed from encrypted -> decrypted and vice versa. By default all guest pages are considered encrypted.

The hypercall exits to userspace to manage the guest shared regions and integrate with the userspace VMM's migration code.

I think this should be exposed to userspace as a capability, rather than as a CPUID bit. Userspace then can enable the capability and set the CPUID bit if it wants.

The reason is that userspace could pass KVM_GET_SUPPORTED_CPUID to KVM_SET_CPUID2 and the hypercall then would break the guest.

I have queued patches 1-6.

For patches 8 and 10 I will post my own version based on my review and feedback.

For guest patches, please repost separately so that x86 maintainers will notice them and ack them.

Hey Paolo,

Quoted 4 lines · Paolo Bonzini

I have queued patches 1-6.

For patches 8 and 10 I will post my own version based on my review and feedback.

can you pls push that tree up to here to a branch somewhere so that ...

Quoted 2 lines

For guest patches, please repost separately so that x86 maintainers will notice them and ack them.

... I can take a look at the guest bits in the full context of the changes?

Yup, for now it's all at kvm/queue and it will land in kvm/next tomorrow (hopefully). The guest interface patches in KVM are very near the top.

+static void set_memory_enc_dec_hypercall(unsigned long vaddr, int npages,

arch/x86/mm/mem_encrypt.c +19 -0

+					bool enc)
+{
+	unsigned long sz = npages << PAGE_SHIFT;
+	unsigned long vaddr_end, vaddr_next;
+
+	vaddr_end = vaddr + sz;
+
+	for (; vaddr < vaddr_end; vaddr = vaddr_next) {
+		int psize, pmask, level;
+		unsigned long pfn;
+		pte_t *kpte;
+
+		kpte = lookup_address(vaddr, &level);
+		if (!kpte || pte_none(*kpte))
+			return;
+
+		switch (level) {
+		case PG_LEVEL_4K:
+			pfn = pte_pfn(*kpte);

arch/x86/mm/mem_encrypt.c +6 -1

+}
+
 static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 {
 	pgprot_t old_prot, new_prot;

@@ -286,12 +329,13 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 static int __init early_set_memory_enc_dec(unsigned long vaddr,
 					   unsigned long size, bool enc)
 {
-	unsigned long vaddr_end, vaddr_next;
+	unsigned long vaddr_end, vaddr_next, start;
 	unsigned long psize, pmask;
 	int split_page_size_mask;
 	int level, ret;
 	pte_t *kpte;
 
+	start = vaddr;
 	vaddr_next = vaddr;
 	vaddr_end = vaddr + size;
 

@@ -346,6 +390,8 @@ static int __init early_set_memory_enc_dec(unsigned long vaddr,
 
 	ret = 0;
 
+	set_memory_enc_dec_hypercall(start, PAGE_ALIGN(size) >> PAGE_SHIFT,
+					enc);
 out:
 	__flush_tlb_all();
 	return ret;

@@ -481,6 +527,15 @@ void __init mem_encrypt_init(void)
 	if (sev_active() && !sev_es_active())

arch/x86/mm/mem_encrypt.c +1 -0

+
 	print_mem_encrypt_feature_info();
 }
 

arch/x86/mm/pat/set_memory.c +1 -0

index 16f878c26667..3576b583ac65 100644
@@ -27,6 +27,7 @@
 #include <asm/proto.h>
 #include <asm/memtype.h>
 #include <asm/set_memory.h>
+#include <asm/paravirt.h>
 
 #include "../mm_internal.h"
 

arch/x86/include/asm/paravirt.h static inline void paravirt_arch_exit_mmap(struct mm_struct *mm) · line 88

Quoted 2 lines · Ashish Kalra

arch/x86/include/asm/paravirt.h +2 -0

+static inline void page_encryption_changed(unsigned long vaddr, int npages,
+						bool enc)

When you see a function name "page_encryption_changed", what does that tell you about what that function does?

Dunno but it doesn't tell me a whole lot.

Now look at the other function names in struct pv_mmu_ops.

See the difference?

Quoted 1 line

+static void set_memory_enc_dec_hypercall(unsigned long vaddr, int npages,

If I had to guess what that function does just by reading its name, it sets a memory encryption/decryption hypercall.

Am I close?

Quoted 19 lines

arch/x86/mm/mem_encrypt.c +19 -0

+					bool enc)
+{
+	unsigned long sz = npages << PAGE_SHIFT;
+	unsigned long vaddr_end, vaddr_next;
+
+	vaddr_end = vaddr + sz;
+
+	for (; vaddr < vaddr_end; vaddr = vaddr_next) {
+		int psize, pmask, level;
+		unsigned long pfn;
+		pte_t *kpte;
+
+		kpte = lookup_address(vaddr, &level);
+		if (!kpte || pte_none(*kpte))
+			return;
+
+		switch (level) {
+		case PG_LEVEL_4K:
+			pfn = pte_pfn(*kpte);

arch/x86/mm/mem_encrypt.c void __init sev_setup_arch(void) · line 263

Quoted 10 lines

arch/x86/mm/mem_encrypt.c +10 -0

+			break;
+		case PG_LEVEL_2M:
+			pfn = pmd_pfn(*(pmd_t *)kpte);
+			break;
+		case PG_LEVEL_1G:
+			pfn = pud_pfn(*(pud_t *)kpte);
+			break;
+		default:
+			return;
+		}

Pretty much that same thing is in __set_clr_pte_enc(). Make a helper function pls.

arch/x86/mm/mem_encrypt.c void __init sev_setup_arch(void) · line 272

Quoted 9 lines

arch/x86/mm/mem_encrypt.c +9 -0

+
+		psize = page_level_size(level);
+		pmask = page_level_mask(level);
+
+		kvm_sev_hypercall3(KVM_HC_PAGE_ENC_STATUS,
+				   pfn << PAGE_SHIFT, psize >> PAGE_SHIFT, enc);
+
+		vaddr_next = (vaddr & pmask) + psize;
+	}

As with other patches from Brijesh, that should be a while loop. :)

Quoted 31 lines

arch/x86/mm/mem_encrypt.c +6 -1

+}
+
  static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
  {
  	pgprot_t old_prot, new_prot;

@@ -286,12 +329,13 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
  static int __init early_set_memory_enc_dec(unsigned long vaddr,
  					   unsigned long size, bool enc)
  {
-	unsigned long vaddr_end, vaddr_next;
+	unsigned long vaddr_end, vaddr_next, start;
  	unsigned long psize, pmask;
  	int split_page_size_mask;
  	int level, ret;
  	pte_t *kpte;
 
+	start = vaddr;
  	vaddr_next = vaddr;
  	vaddr_end = vaddr + size;
 

@@ -346,6 +390,8 @@ static int __init early_set_memory_enc_dec(unsigned long vaddr,
 
  	ret = 0;
 
+	set_memory_enc_dec_hypercall(start, PAGE_ALIGN(size) >> PAGE_SHIFT,
+					enc);
  out:
  	__flush_tlb_all();
  	return ret;

@@ -481,6 +527,15 @@ void __init mem_encrypt_init(void)
  	if (sev_active() && !sev_es_active())

arch/x86/mm/mem_encrypt.c void __init mem_encrypt_init(void) · line 537

Quoted 10 lines

arch/x86/mm/mem_encrypt.c +8 -0

  		static_branch_enable(&sev_enable_key);
 
+#ifdef CONFIG_PARAVIRT
+	/*
+	 * With SEV, we need to make a hypercall when page encryption state is
+	 * changed.
+	 */
+	if (sev_active())
+		pv_ops.mmu.page_encryption_changed = set_memory_enc_dec_hypercall;
+#endif

There's already a sev_active() check above it. Merge the two pls.

Quoted 17 lines

arch/x86/mm/mem_encrypt.c +1 -0

+
  	print_mem_encrypt_feature_info();
  }
 

arch/x86/mm/pat/set_memory.c +1 -0

index 16f878c26667..3576b583ac65 100644
@@ -27,6 +27,7 @@
  #include <asm/proto.h>
  #include <asm/memtype.h>
  #include <asm/set_memory.h>
+#include <asm/paravirt.h>
 
  #include "../mm_internal.h"
 

arch/x86/mm/pat/set_memory.c static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc) · line 2019

Quoted 7 lines

arch/x86/mm/pat/set_memory.c +4 -0

@@ -2012,6 +2013,12 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
  	 */
  	cpa_flush(&cpa, 0);
 
+	/* Notify hypervisor that a given memory range is mapped encrypted
+	 * or decrypted. The hypervisor will use this information during the
+	 * VM migration.
+	 */

Kernel comments style is:

/*
* A sentence ending with a full-stop.
* Another sentence. ...
* More sentences. ...
*/

arch/x86/include/asm/paravirt.h static inline void paravirt_arch_exit_mmap(struct mm_struct *mm) · line 88

Quoted 2 lines · Ashish Kalra

arch/x86/include/asm/paravirt.h +2 -0

+static inline void page_encryption_changed(unsigned long vaddr, int npages,
+						bool enc)

When you see a function name "page_encryption_changed", what does that tell you about what that function does?

Dunno but it doesn't tell me a whole lot.

Now look at the other function names in struct pv_mmu_ops.

See the difference?

Quoted 1 line

+static void set_memory_enc_dec_hypercall(unsigned long vaddr, int npages,

If I had to guess what that function does just by reading its name, it sets a memory encryption/decryption hypercall.

Am I close?

Quoted 24 lines

arch/x86/mm/mem_encrypt.c +24 -0

+					bool enc)
+{
+	unsigned long sz = npages << PAGE_SHIFT;
+	unsigned long vaddr_end, vaddr_next;
+
+	vaddr_end = vaddr + sz;
+
+	for (; vaddr < vaddr_end; vaddr = vaddr_next) {
+		int psize, pmask, level;
+		unsigned long pfn;
+		pte_t *kpte;
+
+		kpte = lookup_address(vaddr, &level);
+		if (!kpte || pte_none(*kpte))
+			return;
+
+		switch (level) {
+		case PG_LEVEL_4K:
+			pfn = pte_pfn(*kpte);
+			break;
+		case PG_LEVEL_2M:
+			pfn = pmd_pfn(*(pmd_t *)kpte);
+			break;
+		case PG_LEVEL_1G:

arch/x86/mm/mem_encrypt.c void __init sev_setup_arch(void) · line 263

Quoted 5 lines

arch/x86/mm/mem_encrypt.c +5 -0

+			pfn = pud_pfn(*(pud_t *)kpte);
+			break;
+		default:
+			return;
+		}

Pretty much that same thing is in __set_clr_pte_enc(). Make a helper function pls.

arch/x86/mm/mem_encrypt.c void __init sev_setup_arch(void) · line 272

Quoted 9 lines

arch/x86/mm/mem_encrypt.c +9 -0

+
+		psize = page_level_size(level);
+		pmask = page_level_mask(level);
+
+		kvm_sev_hypercall3(KVM_HC_PAGE_ENC_STATUS,
+				   pfn << PAGE_SHIFT, psize >> PAGE_SHIFT, enc);
+
+		vaddr_next = (vaddr & pmask) + psize;
+	}

As with other patches from Brijesh, that should be a while loop. :)

Quoted 33 lines

arch/x86/mm/mem_encrypt.c +6 -1

+}
+
 static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 {
 	pgprot_t old_prot, new_prot;

@@ -286,12 +329,13 @@ static void __init __set_clr_pte_enc(pte_t *kpte, int level, bool enc)
 static int __init early_set_memory_enc_dec(unsigned long vaddr,
 					   unsigned long size, bool enc)
 {
-	unsigned long vaddr_end, vaddr_next;
+	unsigned long vaddr_end, vaddr_next, start;
 	unsigned long psize, pmask;
 	int split_page_size_mask;
 	int level, ret;
 	pte_t *kpte;
 
+	start = vaddr;
 	vaddr_next = vaddr;
 	vaddr_end = vaddr + size;
 

@@ -346,6 +390,8 @@ static int __init early_set_memory_enc_dec(unsigned long vaddr,
 
 	ret = 0;
 
+	set_memory_enc_dec_hypercall(start, PAGE_ALIGN(size) >> PAGE_SHIFT,
+					enc);
 out:
 	__flush_tlb_all();
 	return ret;

@@ -481,6 +527,15 @@ void __init mem_encrypt_init(void)
 	if (sev_active() && !sev_es_active())
 		static_branch_enable(&sev_enable_key);
 

arch/x86/mm/mem_encrypt.c void __init mem_encrypt_init(void) · line 537

Quoted 8 lines

arch/x86/mm/mem_encrypt.c +8 -0

+#ifdef CONFIG_PARAVIRT
+	/*
+	 * With SEV, we need to make a hypercall when page encryption state is
+	 * changed.
+	 */
+	if (sev_active())
+		pv_ops.mmu.page_encryption_changed = set_memory_enc_dec_hypercall;
+#endif

There's already a sev_active() check above it. Merge the two pls.

Quoted 17 lines

arch/x86/mm/mem_encrypt.c +1 -0

+
 	print_mem_encrypt_feature_info();
 }
 

arch/x86/mm/pat/set_memory.c +1 -0

index 16f878c26667..3576b583ac65 100644
@@ -27,6 +27,7 @@
 #include <asm/proto.h>
 #include <asm/memtype.h>
 #include <asm/set_memory.h>
+#include <asm/paravirt.h>
 
 #include "../mm_internal.h"
 

arch/x86/mm/pat/set_memory.c static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc) · line 2019

Quoted 7 lines

arch/x86/mm/pat/set_memory.c +4 -0

@@ -2012,6 +2013,12 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc)
 	 */
 	cpa_flush(&cpa, 0);
 
+	/* Notify hypervisor that a given memory range is mapped encrypted
+	 * or decrypted. The hypervisor will use this information during the
+	 * VM migration.
+	 */

Kernel comments style is:

/*
* A sentence ending with a full-stop.
* Another sentence. ...
* More sentences. ...
*/

Signature · 5 lines

-- 
Regards/Gruss,
    Boris.

https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpeople.kernel.org%2Ftglx%2Fnotes-about-netiquette&data=04%7C01%7CAshish.Kalra%40amd.com%7Cf953299226ec42b5077308d904ad427c%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637545964477197662%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=XS9tvx%2BlDPCKGFgsv7jruSrF6kUzAMIqUhBke7rtO5k%3D&reserved=0

Quoted 11 lines

arch/x86/mm/mem_encrypt.c void __init sev_setup_arch(void) · line 272

Quoted 9 lines

arch/x86/mm/mem_encrypt.c +9 -0

+
+		psize = page_level_size(level);
+		pmask = page_level_mask(level);
+
+		kvm_sev_hypercall3(KVM_HC_PAGE_ENC_STATUS,
+				   pfn << PAGE_SHIFT, psize >> PAGE_SHIFT, enc);
+
+		vaddr_next = (vaddr & pmask) + psize;
+	}

As with other patches from Brijesh, that should be a while loop. :)

I see that early_set_memory_enc_dec() is also using a for loop, so which patches are you referring to ?

Yes, both have some common code, but it is only this page level/size
...

I see that early_set_memory_enc_dec() is also using a for loop, so which patches are you referring to ?

The words are right but the order is wrong (more like "hypercall to set some memory's encrypted/decrypted state"). Perhaps? kvm_hypercall_set_page_enc_status.

page_encryption_changed does not sound bad to me though, it's a notification-like function name. Maybe notify_page_enc_status_changed?

From: Ashish Kalra <[email protected]>

The guest support for detecting and enabling SEV Live migration feature uses the following logic :

- kvm_init_plaform() invokes check_kvm_sev_migration() which checks if its booted under the EFI

- If not EFI,

i) check for the KVM_FEATURE_CPUID

arch/x86/kernel/kvm.c +1 -0

index 78bb0fae3982..94ef16d263a7 100644
@@ -26,6 +26,7 @@
 #include <linux/kprobes.h>
 #include <linux/nmi.h>
 #include <linux/swait.h>
+#include <linux/efi.h>
 #include <asm/timer.h>
 #include <asm/cpu.h>
 #include <asm/traps.h>

Quoted 11 lines · Ashish Kalra

From: Ashish Kalra <[email protected]>

The guest support for detecting and enabling SEV Live migration feature uses the following logic :

- kvm_init_plaform() invokes check_kvm_sev_migration() which checks if its booted under the EFI

- If not EFI,

i) check for the KVM_FEATURE_CPUID

Where do you do that?

$ git grep KVM_FEATURE_CPUID
$

Do you mean

kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)

per chance?

Quoted 13 lines

arch/x86/kernel/kvm.c +1 -0

index 78bb0fae3982..94ef16d263a7 100644
@@ -26,6 +26,7 @@
 #include <linux/kprobes.h>
 #include <linux/nmi.h>
 #include <linux/swait.h>
+#include <linux/efi.h>
 #include <asm/timer.h>
 #include <asm/cpu.h>
 #include <asm/traps.h>

arch/x86/kernel/kvm.c static inline void __set_percpu_decrypted(void *ptr, unsigned long size) · line 433

Quoted 4 lines

arch/x86/kernel/kvm.c +1 -0

@@ -429,6 +430,59 @@ static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
 	early_set_memory_decrypted((unsigned long) ptr, size);
 }
 
+static int __init setup_kvm_sev_migration(void)

kvm_init_sev_migration() or so.

...

arch/x86/kernel/kvm.c EXPORT_SYMBOL_GPL(sev_enable_key); · line 53

Quoted 5 lines

arch/x86/kernel/kvm.c +1 -0

@@ -48,6 +50,8 @@ EXPORT_SYMBOL_GPL(sev_enable_key);
 
 bool sev_enabled __section(".data");
 
+bool sev_live_migration_enabled __section(".data");

Pls add a function called something like:

bool sev_feature_enabled(enum sev_feature)

and gets SEV_FEATURE_LIVE_MIGRATION and then use it instead of adding yet another boolean which contains whether some aspect of SEV has been enabled or not.

Then add a

static enum sev_feature sev_features;

in mem_encrypt.c and that function above will query that sev_features enum for set flags.

Then, if you feel bored, you could convert sme_active, sev_active, sev_es_active, mem_encrypt_active and whetever else code needs to query any aspect of SEV being enabled or not, to that function.

arch/x86/kernel/kvm.c EXPORT_SYMBOL_GPL(sev_enable_key); · line 57

Quoted 4 lines

arch/x86/kernel/kvm.c +4 -0

+void __init check_kvm_sev_migration(void)
+{
+	if (sev_active() &&
+	    kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)) {

Save an indentation level:

	if (!sev_active() ||
	    !kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION))
		return;

arch/x86/kernel/kvm.c EXPORT_SYMBOL_GPL(sev_enable_key);

Quoted 4 lines

arch/x86/kernel/kvm.c +4 -0

+		unsigned long nr_pages;
+		int i;
+
+		pr_info("KVM enable live migration\n");

That should be at the end of the function and say:

		pr_info("KVM live migration enabled.\n");

arch/x86/kernel/kvm.c

Quoted 1 line

arch/x86/kernel/kvm.c +1 -0

+		WRITE_ONCE(sev_live_migration_enabled, true);

Why WRITE_ONCE?

And that needs to go to the end of the function too.

Thx.

Signature · 4 lines

Regards/Gruss,
    Boris.

https://nam11.safelinks.protection.outlook.com/?url=https%3A%2F%2Fpeople.kernel.org%2Ftglx%2Fnotes-about-netiquette&data=04%7C01%7CAshish.Kalra%40amd.com%7Cfe47697d718c4326b62108d904d3e9ad%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637546130496140162%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=d%2F%2Bx8t8R7zJclA7ENc%2Fxwt5%2FU13m%2FWObem2Hq8yH190%3D&reserved=0

Yes, the above mentions to get KVM_FEATURE_CPUID and then check if live migration feature is supported, i.e., kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION). The above comments are written more generically.

Just to ensure that the sev_live_migration_enabled is set to TRUE before it is used immediately next in the function.

Quoted 11 lines · Ashish Kalra

From: Ashish Kalra <[email protected]>

The guest support for detecting and enabling SEV Live migration feature uses the following logic :

- kvm_init_plaform() invokes check_kvm_sev_migration() which checks if its booted under the EFI

- If not EFI,

i) check for the KVM_FEATURE_CPUID

Where do you do that?

$ git grep KVM_FEATURE_CPUID
$

Do you mean

kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)

per chance?

Quoted 14 lines

arch/x86/kernel/kvm.c +1 -0

index 78bb0fae3982..94ef16d263a7 100644
@@ -26,6 +26,7 @@
  #include <linux/kprobes.h>
  #include <linux/nmi.h>
  #include <linux/swait.h>
+#include <linux/efi.h>
  #include <asm/timer.h>
  #include <asm/cpu.h>
  #include <asm/traps.h>

arch/x86/kernel/kvm.c static inline void __set_percpu_decrypted(void *ptr, unsigned long size) · line 433

Quoted 4 lines

arch/x86/kernel/kvm.c +1 -0

@@ -429,6 +430,59 @@ static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
  	early_set_memory_decrypted((unsigned long) ptr, size);
  }
 
+static int __init setup_kvm_sev_migration(void)

kvm_init_sev_migration() or so.

...

arch/x86/kernel/kvm.c EXPORT_SYMBOL_GPL(sev_enable_key); · line 53

Quoted 5 lines

arch/x86/kernel/kvm.c +1 -0

@@ -48,6 +50,8 @@ EXPORT_SYMBOL_GPL(sev_enable_key);
 
  bool sev_enabled __section(".data");
 
+bool sev_live_migration_enabled __section(".data");

Pls add a function called something like:

bool sev_feature_enabled(enum sev_feature)

and gets SEV_FEATURE_LIVE_MIGRATION and then use it instead of adding yet another boolean which contains whether some aspect of SEV has been enabled or not.

Then add a

static enum sev_feature sev_features;

in mem_encrypt.c and that function above will query that sev_features enum for set flags.

+static int __init setup_kvm_sev_migration(void)

Quoted 15 lines · Borislav Petkov

Quoted 11 lines · Ashish Kalra

From: Ashish Kalra <[email protected]>

The guest support for detecting and enabling SEV Live migration feature uses the following logic :

- kvm_init_plaform() invokes check_kvm_sev_migration() which checks if its booted under the EFI

- If not EFI,

i) check for the KVM_FEATURE_CPUID

Where do you do that?

Quoted 8 lines

$ git grep KVM_FEATURE_CPUID
$

Do you mean

kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)

per chance?

Yep. Or KVM_CPUID_FEATURES perhaps.

Quoted 34 lines

Quoted 14 lines

arch/x86/kernel/kvm.c +1 -0

index 78bb0fae3982..94ef16d263a7 100644
@@ -26,6 +26,7 @@
  #include <linux/kprobes.h>
  #include <linux/nmi.h>
  #include <linux/swait.h>
+#include <linux/efi.h>
  #include <asm/timer.h>
  #include <asm/cpu.h>
  #include <asm/traps.h>

arch/x86/kernel/kvm.c static inline void __set_percpu_decrypted(void *ptr, unsigned long size) · line 432

Quoted 3 lines

arch/x86/kernel/kvm.c +1 -0

@@ -429,6 +430,59 @@ static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
  	early_set_memory_decrypted((unsigned long) ptr, size);
  }
+static int __init setup_kvm_sev_migration(void)

kvm_init_sev_migration() or so.

...

arch/x86/kernel/kvm.c EXPORT_SYMBOL_GPL(sev_enable_key); · line 51

Quoted 3 lines

arch/x86/kernel/kvm.c +1 -0

@@ -48,6 +50,8 @@ EXPORT_SYMBOL_GPL(sev_enable_key);
  bool sev_enabled __section(".data");
+bool sev_live_migration_enabled __section(".data");

Pls add a function called something like:

bool sev_feature_enabled(enum sev_feature)

and gets SEV_FEATURE_LIVE_MIGRATION and then use it instead of adding yet another boolean which contains whether some aspect of SEV has been enabled or not.

Quoted 6 lines

Then add a

static enum sev_feature sev_features;

in mem_encrypt.c and that function above will query that sev_features enum for set flags.

Even better: let's stop callings things SEV/SEV_ES. Long term we want anyway to use things like mem_encrypt_enabled (SEV), guest_instruction_trap_enabled (SEV/ES), etc.

For this one we don't need a bool at all, we can simply check whether the pvop points to paravirt_nop. Also keep everything but the BSS handling in arch/x86/kernel/kvm.c. Only the BSS handling should be in arch/x86/mm/mem_encrypt.c. This way all KVM paravirt hypercalls and MSRs are in kvm.c.

That is:

void kvm_init_platform(void)

{
	if (sev_active() &&
	    kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)) {
		pv_ops.mmu.notify_page_enc_status_changed =
			kvm_sev_hc_page_enc_status;
		/* this takes care of bss_decrypted */
		early_set_page_enc_status();
		if (!efi_enabled(EFI_BOOT))
			wrmsrl(MSR_KVM_SEV_LIVE_MIGRATION,
			       KVM_SEV_LIVE_MIGRATION_ENABLED);
	}
	/* existing kvm_init_platform code goes here */
}

// the pvop is changed to take the pfn, so that the vaddr loop // is not KVM specific
static inline void notify_page_enc_status_changed(unsigned long pfn,
int npages, bool enc)

{
	PVOP_VCALL3(mmu.page_encryption_changed, pfn, npages, enc);
}

static void notify_addr_enc_status_changed(unsigned long addr,
int numpages, bool enc)
{

#ifdef CONFIG_PARAVIRT
	if (pv_ops.mmu.notify_page_enc_status_changed == paravirt_nop)
		return;

	/* the body of set_memory_enc_dec_hypercall goes here */
	for (; vaddr < vaddr_end; vaddr = vaddr_next) {
		...
		notify_page_enc_status_changed(pfn, psize >> PAGE_SHIFT,
					       enc);
		vaddr_next = (vaddr & pmask) + psize;
	}

#endif
}

static int __set_memory_enc_dec(unsigned long addr,
int numpages, bool enc)

{
	...
 	cpa_flush(&cpa, 0);
	notify_addr_enc_status_changed(addr, numpages, enc);

return ret;
}

Quoted 1 line

+static int __init setup_kvm_sev_migration(void)

Please rename this to include efi in the function name.

arch/x86/mm/mem_encrypt.c bool force_dma_unencrypted(struct device *dev) · line 527

Quoted 9 lines

arch/x86/mm/mem_encrypt.c +8 -0

+		 */
+		if (!efi_enabled(EFI_BOOT))
+			wrmsrl(MSR_KVM_SEV_LIVE_MIGRATION,
+			       KVM_SEV_LIVE_MIGRATION_ENABLED);
+		} else {
+			pr_info("KVM enable live migration feature unsupported\n");
+		}
+}

I think this pr_info is incorrect, because it can still be enabled in the late_initcall. Just remove it as in the sketch above.

Paolo

Hello Paolo,

The earlier patch#10 of SEV live migration patches which is now part of the guest interface patches used to define KVM_FEATURE_SEV_LIVE_MIGRATION.

So now, will the guest patches need to define this feature ?

Thanks,
Ashish

Quoted 149 lines · Paolo Bonzini

Quoted 15 lines · Borislav Petkov

Quoted 11 lines · Ashish Kalra

From: Ashish Kalra <[email protected]>

The guest support for detecting and enabling SEV Live migration feature uses the following logic :

- kvm_init_plaform() invokes check_kvm_sev_migration() which checks if its booted under the EFI

- If not EFI,

i) check for the KVM_FEATURE_CPUID

Where do you do that?

Quoted 8 lines

$ git grep KVM_FEATURE_CPUID
$

Do you mean

kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)

per chance?

Yep. Or KVM_CPUID_FEATURES perhaps.

Quoted 34 lines

Quoted 14 lines

arch/x86/kernel/kvm.c +1 -0

index 78bb0fae3982..94ef16d263a7 100644
@@ -26,6 +26,7 @@
  #include <linux/kprobes.h>
  #include <linux/nmi.h>
  #include <linux/swait.h>
+#include <linux/efi.h>
  #include <asm/timer.h>
  #include <asm/cpu.h>
  #include <asm/traps.h>

arch/x86/kernel/kvm.c static inline void __set_percpu_decrypted(void *ptr, unsigned long size) · line 432

Quoted 3 lines

arch/x86/kernel/kvm.c +1 -0

@@ -429,6 +430,59 @@ static inline void __set_percpu_decrypted(void *ptr, unsigned long size)
  	early_set_memory_decrypted((unsigned long) ptr, size);
  }
+static int __init setup_kvm_sev_migration(void)

kvm_init_sev_migration() or so.

...

arch/x86/kernel/kvm.c EXPORT_SYMBOL_GPL(sev_enable_key); · line 51

Quoted 3 lines

arch/x86/kernel/kvm.c +1 -0

@@ -48,6 +50,8 @@ EXPORT_SYMBOL_GPL(sev_enable_key);
  bool sev_enabled __section(".data");
+bool sev_live_migration_enabled __section(".data");

Pls add a function called something like:

bool sev_feature_enabled(enum sev_feature)

and gets SEV_FEATURE_LIVE_MIGRATION and then use it instead of adding yet another boolean which contains whether some aspect of SEV has been enabled or not.

Quoted 6 lines

Then add a

static enum sev_feature sev_features;

in mem_encrypt.c and that function above will query that sev_features enum for set flags.

Even better: let's stop callings things SEV/SEV_ES. Long term we want anyway to use things like mem_encrypt_enabled (SEV), guest_instruction_trap_enabled (SEV/ES), etc.

For this one we don't need a bool at all, we can simply check whether the pvop points to paravirt_nop. Also keep everything but the BSS handling in arch/x86/kernel/kvm.c. Only the BSS handling should be in arch/x86/mm/mem_encrypt.c. This way all KVM paravirt hypercalls and MSRs are in kvm.c.

That is:

void kvm_init_platform(void)

{
	if (sev_active() &&
	    kvm_para_has_feature(KVM_FEATURE_SEV_LIVE_MIGRATION)) {
		pv_ops.mmu.notify_page_enc_status_changed =
			kvm_sev_hc_page_enc_status;
		/* this takes care of bss_decrypted */
		early_set_page_enc_status();
		if (!efi_enabled(EFI_BOOT))
			wrmsrl(MSR_KVM_SEV_LIVE_MIGRATION,
			       KVM_SEV_LIVE_MIGRATION_ENABLED);
	}
	/* existing kvm_init_platform code goes here */
}

// the pvop is changed to take the pfn, so that the vaddr loop // is not KVM specific
static inline void notify_page_enc_status_changed(unsigned long pfn,
int npages, bool enc)

{
	PVOP_VCALL3(mmu.page_encryption_changed, pfn, npages, enc);
}

static void notify_addr_enc_status_changed(unsigned long addr,
int numpages, bool enc)
{

#ifdef CONFIG_PARAVIRT
	if (pv_ops.mmu.notify_page_enc_status_changed == paravirt_nop)
		return;

	/* the body of set_memory_enc_dec_hypercall goes here */
	for (; vaddr < vaddr_end; vaddr = vaddr_next) {
		...
		notify_page_enc_status_changed(pfn, psize >> PAGE_SHIFT,
					       enc);
		vaddr_next = (vaddr & pmask) + psize;
	}

#endif
}

static int __set_memory_enc_dec(unsigned long addr,
int numpages, bool enc)

{
	...
 	cpa_flush(&cpa, 0);
	notify_addr_enc_status_changed(addr, numpages, enc);

return ret;
}

Quoted 1 line

+static int __init setup_kvm_sev_migration(void)

Please rename this to include efi in the function name.

arch/x86/mm/mem_encrypt.c bool force_dma_unencrypted(struct device *dev) · line 527

Quoted 9 lines

arch/x86/mm/mem_encrypt.c +8 -0

+		 */
+		if (!efi_enabled(EFI_BOOT))
+			wrmsrl(MSR_KVM_SEV_LIVE_MIGRATION,
+			       KVM_SEV_LIVE_MIGRATION_ENABLED);
+		} else {
+			pr_info("KVM enable live migration feature unsupported\n");
+		}
+}

I think this pr_info is incorrect, because it can still be enabled in the late_initcall. Just remove it as in the sketch above.

Paolo