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Subject[PATCH 2/3] KVM: x86: always expose VIRT_SSBD to guests
Date
Even though it is preferrable to use SPEC_CTRL (represented by
X86_FEATURE_AMD_SSBD) instead of VIRT_SPEC, VIRT_SPEC is always
supported anyway because otherwise it would be impossible to
migrate from old to new CPUs. Make this apparent in the
result of KVM_GET_SUPPORTED_CPUID as well.

While at it, reuse X86_FEATURE_* constants for the SVM leaf too.

However, we need to hide the bit on Intel processors, so move
the setting to svm_set_supported_cpuid.

Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reported-by: Eduardo Habkost <ehabkost@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/svm.c | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index e3d3b2128f2b..c5120a9519f3 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -68,10 +68,8 @@
#define SEG_TYPE_LDT 2
#define SEG_TYPE_BUSY_TSS16 3

-#define SVM_FEATURE_NPT (1 << 0)
#define SVM_FEATURE_LBRV (1 << 1)
#define SVM_FEATURE_SVML (1 << 2)
-#define SVM_FEATURE_NRIP (1 << 3)
#define SVM_FEATURE_TSC_RATE (1 << 4)
#define SVM_FEATURE_VMCB_CLEAN (1 << 5)
#define SVM_FEATURE_FLUSH_ASID (1 << 6)
@@ -5933,6 +5931,8 @@ static void svm_cpuid_update(struct kvm_vcpu *vcpu)
guest_cpuid_clear(vcpu, X86_FEATURE_X2APIC);
}

+#define F(x) bit(X86_FEATURE_##x)
+
static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
{
switch (func) {
@@ -5944,6 +5944,11 @@ static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)
if (nested)
entry->ecx |= (1 << 2); /* Set SVM bit */
break;
+ case 0x80000008:
+ if (boot_cpu_has(X86_FEATURE_LS_CFG_SSBD) ||
+ boot_cpu_has(X86_FEATURE_AMD_SSBD))
+ entry->ebx |= F(VIRT_SSBD);
+ break;
case 0x8000000A:
entry->eax = 1; /* SVM revision 1 */
entry->ebx = 8; /* Lets support 8 ASIDs in case we add proper
@@ -5954,11 +5959,11 @@ static void svm_set_supported_cpuid(u32 func, struct kvm_cpuid_entry2 *entry)

/* Support next_rip if host supports it */
if (boot_cpu_has(X86_FEATURE_NRIPS))
- entry->edx |= SVM_FEATURE_NRIP;
+ entry->edx |= F(NRIPS);

/* Support NPT for the guest if enabled */
if (npt_enabled)
- entry->edx |= SVM_FEATURE_NPT;
+ entry->edx |= F(NPT);

break;
case 0x8000001F:
--
1.8.3.1

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