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kvm: x86: ensure pv_cpuid.features is initialized when enabling cap

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Make the paravirtual cpuid enforcement mechanism idempotent to ioctl()
ordering by updating pv_cpuid.features whenever userspace requests the
capability. Extract this update out of kvm_update_cpuid_runtime() into a
new helper function and move its other call site into
kvm_vcpu_after_set_cpuid() where it more likely belongs.

Fixes: 66570e966d ("kvm: x86: only provide PV features if enabled in guest's CPUID")
Signed-off-by: Oliver Upton <oupton@google.com>
Reviewed-by: Peter Shier <pshier@google.com>
Message-Id: <20201027231044.655110-5-oupton@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Oliver Upton 2020-10-27 16:10:42 -07:00 committed by Paolo Bonzini
parent 1930e5ddce
commit 01b4f510b9
3 changed files with 19 additions and 7 deletions
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23
arch/x86/kvm/cpuid.c
View File

@ -90,6 +90,20 @@ static int kvm_check_cpuid(struct kvm_cpuid_entry2 *entries, int nent)
return 0;
}
void kvm_update_pv_runtime(struct kvm_vcpu *vcpu)
{
struct kvm_cpuid_entry2 *best;
best = kvm_find_cpuid_entry(vcpu, KVM_CPUID_FEATURES, 0);
/*
* save the feature bitmap to avoid cpuid lookup for every PV
* operation
*/
if (best)
vcpu->arch.pv_cpuid.features = best->eax;
}
void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
{
struct kvm_cpuid_entry2 *best;
@ -124,13 +138,6 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
(best->eax & (1 << KVM_FEATURE_PV_UNHALT)))
best->eax &= ~(1 << KVM_FEATURE_PV_UNHALT);
/*
* save the feature bitmap to avoid cpuid lookup for every PV
* operation
*/
if (best)
vcpu->arch.pv_cpuid.features = best->eax;
if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT)) {
best = kvm_find_cpuid_entry(vcpu, 0x1, 0);
if (best)
@ -162,6 +169,8 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu)
vcpu->arch.guest_supported_xcr0 =
(best->eax | ((u64)best->edx << 32)) & supported_xcr0;
kvm_update_pv_runtime(vcpu);
vcpu->arch.maxphyaddr = cpuid_query_maxphyaddr(vcpu);
kvm_mmu_reset_context(vcpu);

1
arch/x86/kvm/cpuid.h
View File

@ -11,6 +11,7 @@ extern u32 kvm_cpu_caps[NCAPINTS] __read_mostly;
void kvm_set_cpu_caps(void);
void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu);
void kvm_update_pv_runtime(struct kvm_vcpu *vcpu);
struct kvm_cpuid_entry2 *kvm_find_cpuid_entry(struct kvm_vcpu *vcpu,
u32 function, u32 index);
int kvm_dev_ioctl_get_cpuid(struct kvm_cpuid2 *cpuid,

2
arch/x86/kvm/x86.c
View File

@ -4611,6 +4611,8 @@ static int kvm_vcpu_ioctl_enable_cap(struct kvm_vcpu *vcpu,
case KVM_CAP_ENFORCE_PV_FEATURE_CPUID:
vcpu->arch.pv_cpuid.enforce = cap->args[0];
if (vcpu->arch.pv_cpuid.enforce)
kvm_update_pv_runtime(vcpu);
return 0;