Skip to contentSkip to conversation

KVM: SVM: Add initial GHCB protocol version 2 support

PATCH Superseded Joerg Roedel 2 participants 7 messages Sep 13, 2021 – Sep 24, 2021

Subsystems (3)
x86 KVM KVM x86

v3 of 6 Superseded Latest is v6 →

lore
Share & tools
lore

Joerg Roedel

author
#0 lore raw

v3 cover KVM: SVM: Add initial GHCB protocol version 2 support

From: Joerg Roedel <[email protected]>

Hi,

here is a small set of patches which I took from the pending SEV-SNP patch-sets to enable basic support for GHCB protocol version 2.

When SEV-SNP is not supported, only two new MSR protocol VMGEXIT calls need to be supported:

- MSR-based AP-reset-hold
- MSR-based HV-feature-request

These calls are implemented here and then the protocol is lifted to version 2.

This is submitted separately because the MSR-based AP-reset-hold call is required to support kexec/kdump in SEV-ES guests.

Regards,

Joerg

Changes v2->v3:

- Rebased to v5.15-rc1

- Reworked GHCB_MSR access interfaces as suggested by Sean Christopherson.

Brijesh Singh (2):
KVM: SVM: Add support for Hypervisor Feature support MSR protocol
KVM: SVM: Increase supported GHCB protocol version

Joerg Roedel (1):
KVM: SVM: Get rid of set_ghcb_msr() and *ghcb_msr_bits() functions

Tom Lendacky (1):
KVM: SVM: Add support to handle AP reset MSR protocol

 arch/x86/include/asm/kvm_host.h   |  10 ++-
 arch/x86/include/asm/sev-common.h |   9 +++
 arch/x86/include/uapi/asm/svm.h   |   1 +
 arch/x86/kvm/svm/sev.c            | 115 +++++++++++++++++++-----------
 arch/x86/kvm/svm/svm.h            |   3 +-
 arch/x86/kvm/x86.c                |   5 +-
 6 files changed, 98 insertions(+), 45 deletions(-)

base-commit: 6880fa6c56601bb8ed59df6c30fd390cc5f6dd8f

Signature · 1 line
2.33.0
author
#1 lore raw

PATCH v3 1/4 KVM: SVM: Get rid of set_ghcb_msr() and *ghcb_msr_bits() functions

From: Joerg Roedel <[email protected]>

Replace the get_ghcb_msr_bits() function with macros and open code the GHCB MSR setters with hypercall specific helper macros and functions. This will avoid preserving any previous bits in the GHCB-MSR and improves code readability.

Also get rid of the set_ghcb_msr() function and open-code it at its call-sites for better code readability.

Suggested-by Sean Christopherson <[email protected]>
Signed-off-by Joerg Roedel <[email protected]>
---
 arch/x86/include/asm/sev-common.h |  9 +++++
 arch/x86/kvm/svm/sev.c            | 56 +++++++++++--------------------
 2 files changed, 29 insertions(+), 36 deletions(-)
arch/x86/include/asm/sev-common.h +9 -0
index 2cef6c5a52c2..8540972cad04 100644
@@ -50,6 +50,10 @@
 		(GHCB_MSR_CPUID_REQ | \
 		(((unsigned long)reg & GHCB_MSR_CPUID_REG_MASK) << GHCB_MSR_CPUID_REG_POS) | \
 		(((unsigned long)fn) << GHCB_MSR_CPUID_FUNC_POS))
+#define GHCB_MSR_CPUID_FN(msr)		\
+	(((msr) >> GHCB_MSR_CPUID_FUNC_POS) & GHCB_MSR_CPUID_FUNC_MASK)
+#define GHCB_MSR_CPUID_REG(msr)		\
+	(((msr) >> GHCB_MSR_CPUID_REG_POS) & GHCB_MSR_CPUID_REG_MASK)
 
 /* AP Reset Hold */
 #define GHCB_MSR_AP_RESET_HOLD_REQ		0x006

@@ -67,6 +71,11 @@
 #define GHCB_SEV_TERM_REASON(reason_set, reason_val)						  \
 	(((((u64)reason_set) &  GHCB_MSR_TERM_REASON_SET_MASK) << GHCB_MSR_TERM_REASON_SET_POS) | \
 	((((u64)reason_val) & GHCB_MSR_TERM_REASON_MASK) << GHCB_MSR_TERM_REASON_POS))
+#define GHCB_MSR_TERM_REASON_SET(msr)	\
+	(((msr) >> GHCB_MSR_TERM_REASON_SET_POS) & GHCB_MSR_TERM_REASON_SET_MASK)
+#define GHCB_MSR_TERM_REASON(msr)	\
+	(((msr) >> GHCB_MSR_TERM_REASON_POS) & GHCB_MSR_TERM_REASON_MASK)
+
 
 #define GHCB_SEV_ES_REASON_GENERAL_REQUEST	0
 #define GHCB_SEV_ES_REASON_PROTOCOL_UNSUPPORTED	1
arch/x86/kvm/svm/sev.c +20 -36

101 lines not on this page · raw message

Signature · 1 line
2.33.0
maintainer Reviewed-by on v3 1/4
#2 lore raw

Re: [PATCH v3 1/4] KVM: SVM: Get rid of set_ghcb_msr() and *ghcb_msr_bits() functions

Review static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm) · line 2376

Quoted 11 lines · Joerg Roedel

static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)

(quoted diff) +3 -3
@@ -2377,16 +2371,14 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 
 	switch (ghcb_info) {
 	case GHCB_MSR_SEV_INFO_REQ:
-		set_ghcb_msr(svm, GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
-						    GHCB_VERSION_MIN,
-						    sev_enc_bit));
+		svm->vmcb->control.ghcb_gpa = GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
+								GHCB_VERSION_MIN,
+								sev_enc_bit);

Nit, "svm->vmcb->control." can be "control->".

With that fixed,

Reviewed-by Sean Christopherson <[email protected]>
Quoted 25 lines
(quoted diff) +3 -6
 		break;
 	case GHCB_MSR_CPUID_REQ: {
 		u64 cpuid_fn, cpuid_reg, cpuid_value;
 
-		cpuid_fn = get_ghcb_msr_bits(svm,
-					     GHCB_MSR_CPUID_FUNC_MASK,
-					     GHCB_MSR_CPUID_FUNC_POS);
+		cpuid_fn = GHCB_MSR_CPUID_FN(control->ghcb_gpa);
 
 		/* Initialize the registers needed by the CPUID intercept */
 		vcpu->arch.regs[VCPU_REGS_RAX] = cpuid_fn;

@@ -2398,9 +2390,8 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 			break;
 		}
 
-		cpuid_reg = get_ghcb_msr_bits(svm,
-					      GHCB_MSR_CPUID_REG_MASK,
-					      GHCB_MSR_CPUID_REG_POS);
+		cpuid_reg = GHCB_MSR_CPUID_REG(control->ghcb_gpa);
+
 		if (cpuid_reg == 0)
 			cpuid_value = vcpu->arch.regs[VCPU_REGS_RAX];
 		else if (cpuid_reg == 1)

@@ -2410,26 +2401,19 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 		else

Review static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm) · line 2419

Quoted 10 lines
(quoted diff) +1 -6
 			cpuid_value = vcpu->arch.regs[VCPU_REGS_RDX];
 
-		set_ghcb_msr_bits(svm, cpuid_value,
-				  GHCB_MSR_CPUID_VALUE_MASK,
-				  GHCB_MSR_CPUID_VALUE_POS);
+		svm->vmcb->control.ghcb_gpa = ghcb_msr_cpuid_resp(cpuid_reg, cpuid_value);
 
-		set_ghcb_msr_bits(svm, GHCB_MSR_CPUID_RESP,
-				  GHCB_MSR_INFO_MASK,
-				  GHCB_MSR_INFO_POS);

I don't mind using a helper instead of a macro (I completely agree the helper is easier to read), but we should be consistent, i.e. get rid of GHCB_MSR_SEV_INFO. And IMO that helper should handle the min/max version, not the callers. Add this after patch 01 (modulo the above nit)?

From 5c329f9e7156948697955a2745f32df024aa5ee6 Mon Sep 17 00:00:00 2001
From: Sean Christopherson <[email protected]>
Date: Fri, 24 Sep 2021 12:58:31 -0700
Subject: [PATCH] KVM: SVM: Add helper to generate GHCB MSR verson info, and
drop macro

Convert the GHCB_MSR_SEV_INFO macro into a helper function, and have the helper hardcode the min/max versions instead of relying on the caller to do the same. Under no circumstance should different pieces of KVM define different min/max versions.

No functional change intended.

Signed-off-by Sean Christopherson <[email protected]>
---
 arch/x86/include/asm/sev-common.h |  5 -----
 arch/x86/kvm/svm/sev.c            | 24 ++++++++++++++++++------
 arch/x86/kvm/svm/svm.h            |  5 -----
 3 files changed, 18 insertions(+), 16 deletions(-)
arch/x86/include/asm/sev-common.h +0 -5
index 8540972cad04..886c36f0cb16 100644
@@ -24,11 +24,6 @@
 #define GHCB_MSR_VER_MIN_MASK		0xffff
 #define GHCB_MSR_CBIT_POS		24
 #define GHCB_MSR_CBIT_MASK		0xff
-#define GHCB_MSR_SEV_INFO(_max, _min, _cbit)				\
-	((((_max) & GHCB_MSR_VER_MAX_MASK) << GHCB_MSR_VER_MAX_POS) |	\
-	 (((_min) & GHCB_MSR_VER_MIN_MASK) << GHCB_MSR_VER_MIN_POS) |	\
-	 (((_cbit) & GHCB_MSR_CBIT_MASK) << GHCB_MSR_CBIT_POS) |	\
-	 GHCB_MSR_SEV_INFO_RESP)
 #define GHCB_MSR_INFO(v)		((v) & 0xfffUL)
 #define GHCB_MSR_PROTO_MAX(v)		(((v) >> GHCB_MSR_VER_MAX_POS) & GHCB_MSR_VER_MAX_MASK)
 #define GHCB_MSR_PROTO_MIN(v)		(((v) >> GHCB_MSR_VER_MIN_POS) & GHCB_MSR_VER_MIN_MASK)
arch/x86/kvm/svm/sev.c +18 -6
index 7aa6ad4c3118..159b22bb74e4 100644
@@ -2389,6 +2389,22 @@ static u64 ghcb_msr_cpuid_resp(u64 reg, u64 value)
 	return msr;
 }
 
+/* The min/max GHCB version supported by KVM. */
+#define GHCB_VERSION_MAX	1ULL
+#define GHCB_VERSION_MIN	1ULL
+
+static u64 ghcb_msr_version_info(void)
+{
+	u64 msr;
+
+	msr  = GHCB_MSR_SEV_INFO_RESP;
+	msr |= GHCB_VERSION_MAX << GHCB_MSR_VER_MAX_POS;
+	msr |= GHCB_VERSION_MIN << GHCB_MSR_VER_MIN_POS;
+	msr |= sev_enc_bit << GHCB_MSR_CBIT_POS;
+
+	return msr;
+}
+
 static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 {
 	struct vmcb_control_area *control = &svm->vmcb->control;

@@ -2403,9 +2419,7 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 
 	switch (ghcb_info) {
 	case GHCB_MSR_SEV_INFO_REQ:
-		svm->vmcb->control.ghcb_gpa = GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
-								GHCB_VERSION_MIN,
-								sev_enc_bit);
+		control->ghcb_gpa = ghcb_msr_version_info();
 		break;
 	case GHCB_MSR_CPUID_REQ: {
 		u64 cpuid_fn, cpuid_reg, cpuid_value;

@@ -2621,9 +2635,7 @@ void sev_es_vcpu_reset(struct vcpu_svm *svm)
 	 * Set the GHCB MSR value as per the GHCB specification when emulating
 	 * vCPU RESET for an SEV-ES guest.
 	 */
-	svm->vmcb->control.ghcb_gpa = GHCB_MSR_SEV_INFO(GHCB_VERSION_MAX,
-							GHCB_VERSION_MIN,
-							sev_enc_bit);
+	svm->vmcb->control.ghcb_gpa = ghcb_msr_version_info();
 }
 
 void sev_es_prepare_guest_switch(struct vcpu_svm *svm, unsigned int cpu)
arch/x86/kvm/svm/svm.h +0 -5
index 0d7bbe548ac3..68e5f16a0554 100644
@@ -544,11 +544,6 @@ void svm_vcpu_blocking(struct kvm_vcpu *vcpu);
 void svm_vcpu_unblocking(struct kvm_vcpu *vcpu);
 
 /* sev.c */
-
-#define GHCB_VERSION_MAX	1ULL
-#define GHCB_VERSION_MIN	1ULL
-
-
 extern unsigned int max_sev_asid;
 
 void sev_vm_destroy(struct kvm *kvm);

--
2.33.0.685.g46640cef36-goog

author
#3 lore raw

PATCH v3 2/4 KVM: SVM: Add support to handle AP reset MSR protocol

In reply to Joerg Roedel

From: Tom Lendacky <[email protected]>

Add support for AP Reset Hold being invoked using the GHCB MSR protocol, available in version 2 of the GHCB specification.

Signed-off-by Tom Lendacky <[email protected]>
Signed-off-by Brijesh Singh <[email protected]>
Signed-off-by Joerg Roedel <[email protected]>
---
 arch/x86/include/asm/kvm_host.h | 10 ++++++-
 arch/x86/kvm/svm/sev.c          | 48 ++++++++++++++++++++++++++-------
 arch/x86/kvm/x86.c              |  5 +++-
 3 files changed, 51 insertions(+), 12 deletions(-)
arch/x86/include/asm/kvm_host.h +9 -1
index f8f48a7ec577..2f84cda48cdf 100644
@@ -237,6 +237,11 @@ enum x86_intercept_stage;
 	KVM_GUESTDBG_INJECT_DB | \
 	KVM_GUESTDBG_BLOCKIRQ)
 
+enum ap_reset_hold_type {
+	AP_RESET_HOLD_NONE,
+	AP_RESET_HOLD_NAE_EVENT,
+	AP_RESET_HOLD_MSR_PROTO,
+};
 
 #define PFERR_PRESENT_BIT 0
 #define PFERR_WRITE_BIT 1

@@ -909,6 +914,8 @@ struct kvm_vcpu_arch {
 #if IS_ENABLED(CONFIG_HYPERV)
 	hpa_t hv_root_tdp;
 #endif
+
+	enum ap_reset_hold_type reset_hold_type;
 };
 
 struct kvm_lpage_info {

@@ -1675,7 +1682,8 @@ int kvm_fast_pio(struct kvm_vcpu *vcpu, int size, unsigned short port, int in);
 int kvm_emulate_cpuid(struct kvm_vcpu *vcpu);
 int kvm_emulate_halt(struct kvm_vcpu *vcpu);
 int kvm_vcpu_halt(struct kvm_vcpu *vcpu);
-int kvm_emulate_ap_reset_hold(struct kvm_vcpu *vcpu);
+int kvm_emulate_ap_reset_hold(struct kvm_vcpu *vcpu,
+			      enum ap_reset_hold_type type);
 int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu);
 
 void kvm_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg);
arch/x86/kvm/svm/sev.c +38 -10

76 lines not on this page · raw message

arch/x86/kvm/x86.c +4 -1
index 28ef14155726..412a195b07af 100644
@@ -8516,10 +8516,13 @@ int kvm_emulate_halt(struct kvm_vcpu *vcpu)
 }
 EXPORT_SYMBOL_GPL(kvm_emulate_halt);
 
-int kvm_emulate_ap_reset_hold(struct kvm_vcpu *vcpu)
+int kvm_emulate_ap_reset_hold(struct kvm_vcpu *vcpu,
+			      enum ap_reset_hold_type type)
 {
 	int ret = kvm_skip_emulated_instruction(vcpu);
 
+	vcpu->arch.reset_hold_type = type;
+
 	return __kvm_vcpu_halt(vcpu, KVM_MP_STATE_AP_RESET_HOLD, KVM_EXIT_AP_RESET_HOLD) && ret;
 }
 EXPORT_SYMBOL_GPL(kvm_emulate_ap_reset_hold);
Signature · 1 line
2.33.0
author
#4 lore raw

PATCH v3 3/4 KVM: SVM: Add support for Hypervisor Feature support MSR protocol

In reply to Joerg Roedel

From: Brijesh Singh <[email protected]>

Version 2 of the GHCB specification introduced advertisement of supported Hypervisor SEV features. This request is required to support a the GHCB version 2 protocol.

Signed-off-by Brijesh Singh <[email protected]>
Signed-off-by Joerg Roedel <[email protected]>
---
 arch/x86/include/uapi/asm/svm.h |  1 +
 arch/x86/kvm/svm/sev.c          | 19 +++++++++++++++++++
 arch/x86/kvm/svm/svm.h          |  1 +
 3 files changed, 21 insertions(+)
arch/x86/include/uapi/asm/svm.h +1 -0
index efa969325ede..67cf153fe580 100644
@@ -108,6 +108,7 @@
 #define SVM_VMGEXIT_AP_JUMP_TABLE		0x80000005
 #define SVM_VMGEXIT_SET_AP_JUMP_TABLE		0
 #define SVM_VMGEXIT_GET_AP_JUMP_TABLE		1
+#define SVM_VMGEXIT_HYPERVISOR_FEATURES		0x8000fffd
 #define SVM_VMGEXIT_UNSUPPORTED_EVENT		0x8000ffff
 
 /* Exit code reserved for hypervisor/software use */
arch/x86/kvm/svm/sev.c +19 -0
index 8cd1e4ebb4a8..b3fdfccf0499 100644
@@ -2184,6 +2184,7 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
 	case SVM_VMGEXIT_AP_HLT_LOOP:
 	case SVM_VMGEXIT_AP_JUMP_TABLE:
 	case SVM_VMGEXIT_UNSUPPORTED_EVENT:
+	case SVM_VMGEXIT_HYPERVISOR_FEATURES:
 		break;
 	default:
 		goto vmgexit_err;

@@ -2365,6 +2366,16 @@ static u64 ghcb_msr_ap_rst_resp(u64 value)
 	return (u64)GHCB_MSR_AP_RESET_HOLD_RESP | (value << GHCB_DATA_LOW);
 }
 
+static u64 ghcb_msr_hv_feat_resp(u64 value)
+{
+	u64 msr;
+
+	msr  = GHCB_MSR_HV_FT_RESP;
+	msr |= (value << GHCB_DATA_LOW);
+
+	return msr;
+}
+
 static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 {
 	struct vmcb_control_area *control = &svm->vmcb->control;

@@ -2422,6 +2433,9 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 		 */
 		svm->vmcb->control.ghcb_gpa = ghcb_msr_ap_rst_resp(0);
 
+		break;
+	case GHCB_MSR_HV_FT_REQ:
+		svm->vmcb->control.ghcb_gpa = ghcb_msr_hv_feat_resp(GHCB_HV_FT_SUPPORTED);
 		break;
 	case GHCB_MSR_TERM_REQ: {
 		u64 reason_set, reason_code;

@@ -2535,6 +2549,11 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
 		ret = 1;
 		break;
 	}
+	case SVM_VMGEXIT_HYPERVISOR_FEATURES:
+		ghcb_set_sw_exit_info_2(ghcb, GHCB_HV_FT_SUPPORTED);
+
+		ret = 1;
+		break;
 	case SVM_VMGEXIT_UNSUPPORTED_EVENT:
 		vcpu_unimpl(vcpu,
 			    "vmgexit: unsupported event - exit_info_1=%#llx, exit_info_2=%#llx\n",
arch/x86/kvm/svm/svm.h +1 -0
index 524d943f3efc..f019da28ff06 100644
@@ -542,6 +542,7 @@ void svm_vcpu_unblocking(struct kvm_vcpu *vcpu);
 #define GHCB_VERSION_MAX	1ULL
 #define GHCB_VERSION_MIN	1ULL
 
+#define GHCB_HV_FT_SUPPORTED	0
 
 extern unsigned int max_sev_asid;
Signature · 1 line
2.33.0
maintainer
#5 lore raw

Re: [PATCH v3 3/4] KVM: SVM: Add support for Hypervisor Feature support MSR protocol

arch/x86/kvm/svm/svm.h void svm_vcpu_unblocking(struct kvm_vcpu *vcpu); · line 545

Quoted 9 lines · Joerg Roedel
arch/x86/kvm/svm/svm.h +1 -0
index 524d943f3efc..f019da28ff06 100644
@@ -542,6 +542,7 @@ void svm_vcpu_unblocking(struct kvm_vcpu *vcpu);
 #define GHCB_VERSION_MAX	1ULL
 #define GHCB_VERSION_MIN	1ULL
 
+#define GHCB_HV_FT_SUPPORTED	0

I'd prefer to keep these SEV-only defines in sev.c. I also think it should have KVM somewhere in the name, a la KVM_SUPPORTED_XCR0, e.g. KVM_SUPPORTED_GHCB_FEATURES?

author
#6 lore raw

PATCH v3 4/4 KVM: SVM: Increase supported GHCB protocol version

In reply to Joerg Roedel

From: Brijesh Singh <[email protected]>

Now that KVM has basic support for version 2 of the GHCB specification, bump the maximum supported protocol version. The SNP specific functions are still missing, but those are only required when the Hypervisor supports running SNP guests.

Signed-off-by Brijesh Singh <[email protected]>
Signed-off-by Joerg Roedel <[email protected]>
---
 arch/x86/kvm/svm/svm.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
arch/x86/kvm/svm/svm.h +1 -1
index f019da28ff06..0650f51f7de0 100644
@@ -539,7 +539,7 @@ void svm_vcpu_unblocking(struct kvm_vcpu *vcpu);
 
 /* sev.c */
 
-#define GHCB_VERSION_MAX	1ULL
+#define GHCB_VERSION_MAX	2ULL
 #define GHCB_VERSION_MIN	1ULL
 
 #define GHCB_HV_FT_SUPPORTED	0
Signature · 1 line
2.33.0