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KVM: x86: Correct adjustment of KVM_CPUID_FEATURES

PATCH Applied Paul Durrant 2 participants 4 messages Nov 5, 2021 – Nov 11, 2021

Subsystems (5)
Stable branch x86 KVM KVM x86 +1 more subsystems
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Paul Durrant

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#0 lore raw

v2 cover KVM: x86: Correct adjustment of KVM_CPUID_FEATURES

v2: Pre-requisite patch from Sean.

Paul Durrant (1):
KVM: x86: Make sure KVM_CPUID_FEATURES really are KVM_CPUID_FEATURES

Sean Christopherson (1):
KVM: x86: Add helper to consolidate core logic of SET_CPUID{2} flows

 arch/x86/include/asm/kvm_host.h      |  1 +
 arch/x86/include/asm/processor.h     |  5 +-
 arch/x86/include/uapi/asm/kvm_para.h |  1 +
 arch/x86/kernel/kvm.c                |  2 +-
 arch/x86/kvm/cpuid.c                 | 93 +++++++++++++++++++---------
 5 files changed, 71 insertions(+), 31 deletions(-)

---
Cc: Paolo Bonzini <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Jim Mattson <[email protected]>
Cc: Joerg Roedel <[email protected]>

author
#1 lore raw

PATCH v2 1/2 KVM: x86: Add helper to consolidate core logic of SET_CPUID{2} flows

From: Sean Christopherson <[email protected]>

Move the core logic of SET_CPUID and SET_CPUID2 to a common helper, the only difference between the two ioctls() is the format of the userspace struct. A future fix will add yet more code to the core logic.

No functional change intended.

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

---
Cc: Paolo Bonzini <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Jim Mattson <[email protected]>
Cc: Joerg Roedel <[email protected]>

v2:
- New in v2

---
 arch/x86/kvm/cpuid.c | 47 ++++++++++++++++++++++----------------------
 1 file changed, 24 insertions(+), 23 deletions(-)
arch/x86/kvm/cpuid.c +24 -23
index 2d70edb0f323..41529c168e91 100644
@@ -239,6 +239,25 @@ u64 kvm_vcpu_reserved_gpa_bits_raw(struct kvm_vcpu *vcpu)
 	return rsvd_bits(cpuid_maxphyaddr(vcpu), 63);
 }
 
+static int kvm_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2,
+                        int nent)
+{
+    int r;
+
+    r = kvm_check_cpuid(e2, nent);
+    if (r)
+        return r;
+
+    kvfree(vcpu->arch.cpuid_entries);
+    vcpu->arch.cpuid_entries = e2;
+    vcpu->arch.cpuid_nent = nent;
+
+    kvm_update_cpuid_runtime(vcpu);
+    kvm_vcpu_after_set_cpuid(vcpu);
+
+    return 0;
+}
+
 /* when an old userspace process fills a new kernel module */
 int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
 			     struct kvm_cpuid *cpuid,

@@ -275,18 +294,9 @@ int kvm_vcpu_ioctl_set_cpuid(struct kvm_vcpu *vcpu,
 		e2[i].padding[2] = 0;
 	}
 
-	r = kvm_check_cpuid(e2, cpuid->nent);
-	if (r) {
+	r = kvm_set_cpuid(vcpu, e2, cpuid->nent);
+	if (r)
 		kvfree(e2);
-		goto out_free_cpuid;
-	}
-
-	kvfree(vcpu->arch.cpuid_entries);
-	vcpu->arch.cpuid_entries = e2;
-	vcpu->arch.cpuid_nent = cpuid->nent;
-
-	kvm_update_cpuid_runtime(vcpu);
-	kvm_vcpu_after_set_cpuid(vcpu);
 
 out_free_cpuid:
 	kvfree(e);

@@ -310,20 +320,11 @@ int kvm_vcpu_ioctl_set_cpuid2(struct kvm_vcpu *vcpu,
 			return PTR_ERR(e2);
 	}
 
-	r = kvm_check_cpuid(e2, cpuid->nent);
-	if (r) {
+	r = kvm_set_cpuid(vcpu, e2, cpuid->nent);
+	if (r)
 		kvfree(e2);
-		return r;
-	}
 
-	kvfree(vcpu->arch.cpuid_entries);
-	vcpu->arch.cpuid_entries = e2;
-	vcpu->arch.cpuid_nent = cpuid->nent;
-
-	kvm_update_cpuid_runtime(vcpu);
-	kvm_vcpu_after_set_cpuid(vcpu);
-
-	return 0;
+	return r;
 }
 
 int kvm_vcpu_ioctl_get_cpuid2(struct kvm_vcpu *vcpu,
Signature · 1 line
2.20.1
author
#2 lore raw

PATCH v2 2/2 KVM: x86: Make sure KVM_CPUID_FEATURES really are KVM_CPUID_FEATURES

In reply to Paul Durrant

Currently when kvm_update_cpuid_runtime() runs, it assumes that the KVM_CPUID_FEATURES leaf is located at 0x40000001. This is not true, however, if Hyper-V support is enabled. In this case the KVM leaves will be offset.

This patch introdues as new 'kvm_cpuid_base' field into struct kvm_vcpu_arch to track the location of the KVM leaves and function kvm_update_kvm_cpuid_base() (called from kvm_set_cpuid()) to locate the leaves using the 'KVMKVMKVM\0\0\0' signature (which is now given a definition in kvm_para.h). Adjustment of KVM_CPUID_FEATURES will hence now target the correct leaf.

NOTE: A new for_each_possible_hypervisor_cpuid_base() macro is intoduced
into processor.h to avoid having duplicate code for the iteration over possible hypervisor base leaves.

Signed-off-by Paul Durrant <[email protected]>

---
Cc: Paolo Bonzini <[email protected]>
Cc: Sean Christopherson <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Jim Mattson <[email protected]>
Cc: Joerg Roedel <[email protected]>

v2:
- Added new for_each_possible_hypervisor_cpuid_base() macro
- Added KVM_SIGNATURE definition
- Other amendments as requested by Sean

---
 arch/x86/include/asm/kvm_host.h      |  1 +
 arch/x86/include/asm/processor.h     |  5 ++-
 arch/x86/include/uapi/asm/kvm_para.h |  1 +
 arch/x86/kernel/kvm.c                |  2 +-
 arch/x86/kvm/cpuid.c                 | 46 ++++++++++++++++++++++++----
 5 files changed, 47 insertions(+), 8 deletions(-)
arch/x86/include/asm/kvm_host.h +1 -0
index 88fce6ab4bbd..21133ffa23e9 100644
@@ -725,6 +725,7 @@ struct kvm_vcpu_arch {
 
 	int cpuid_nent;
 	struct kvm_cpuid_entry2 *cpuid_entries;
+	u32 kvm_cpuid_base;
 
 	u64 reserved_gpa_bits;
 	int maxphyaddr;
arch/x86/include/asm/processor.h +4 -1
index 9ad2acaaae9b..726318cda082 100644
@@ -807,11 +807,14 @@ static inline u32 amd_get_nodes_per_socket(void)	{ return 0; }
 static inline u32 amd_get_highest_perf(void)		{ return 0; }
 #endif
 
+#define for_each_possible_hypervisor_cpuid_base(function) \
+	for (function = 0x40000000; function < 0x40010000; function += 0x100)
+
 static inline uint32_t hypervisor_cpuid_base(const char *sig, uint32_t leaves)
 {
 	uint32_t base, eax, signature[3];
 
-	for (base = 0x40000000; base < 0x40010000; base += 0x100) {
+	for_each_possible_hypervisor_cpuid_base(base) {
 		cpuid(base, &eax, &signature[0], &signature[1], &signature[2]);
 
 		if (!memcmp(sig, signature, 12) &&
arch/x86/include/uapi/asm/kvm_para.h +1 -0
index 5146bbab84d4..6e64b27b2c1e 100644
@@ -8,6 +8,7 @@
  * should be used to determine that a VM is running under KVM.
  */
 #define KVM_CPUID_SIGNATURE	0x40000000
+#define KVM_SIGNATURE "KVMKVMKVM\0\0\0"
 
 /* This CPUID returns two feature bitmaps in eax, edx. Before enabling
  * a particular paravirtualization, the appropriate feature bit should
arch/x86/kernel/kvm.c +1 -1
index b656456c3a94..c97859170286 100644
@@ -755,7 +755,7 @@ static noinline uint32_t __kvm_cpuid_base(void)
 		return 0;	/* So we don't blow up on old processors */
 
 	if (boot_cpu_has(X86_FEATURE_HYPERVISOR))
-		return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);
+		return hypervisor_cpuid_base(KVM_SIGNATURE, 0);
 
 	return 0;
 }
arch/x86/kvm/cpuid.c +40 -6

72 lines not on this page · raw message

Signature · 1 line
2.20.1
maintainer Applied
#3 lore raw
In reply to Paul Durrant
Quoted 14 lines · Paul Durrant

v2: Pre-requisite patch from Sean.

Paul Durrant (1):
KVM: x86: Make sure KVM_CPUID_FEATURES really are KVM_CPUID_FEATURES

Sean Christopherson (1):
KVM: x86: Add helper to consolidate core logic of SET_CPUID{2} flows

  arch/x86/include/asm/kvm_host.h      |  1 +
  arch/x86/include/asm/processor.h     |  5 +-
  arch/x86/include/uapi/asm/kvm_para.h |  1 +
  arch/x86/kernel/kvm.c                |  2 +-
  arch/x86/kvm/cpuid.c                 | 93 +++++++++++++++++++---------
  5 files changed, 71 insertions(+), 31 deletions(-)
Quoted 7 lines

---
Cc: Paolo Bonzini <[email protected]>
Cc: Vitaly Kuznetsov <[email protected]>
Cc: Wanpeng Li <[email protected]>
Cc: Jim Mattson <[email protected]>
Cc: Joerg Roedel <[email protected]>

Queued, thanks.

Paolo