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KVM: x86: Update guest cpu_caps at runtime for dynamic CPUID-based features

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When updating guest CPUID entries to emulate runtime behavior, e.g. when
the guest enables a CR4-based feature that is tied to a CPUID flag, also
update the vCPU's cpu_caps accordingly.  This will allow replacing all
usage of guest_cpuid_has() with guest_cpu_cap_has().

Note, this relies on kvm_set_cpuid() taking a snapshot of cpu_caps before
invoking kvm_update_cpuid_runtime(), i.e. when KVM is updating CPUID
entries that *may* become the vCPU's CPUID, so that unwinding to the old
cpu_caps is possible if userspace tries to set bogus CPUID information.

Note #2, none of the features in question use guest_cpu_cap_has() at this
time, i.e. aside from settings bits in cpu_caps, this is a glorified nop.

Cc: Yang Weijiang <weijiang.yang@intel.com>
Cc: Robert Hoo <robert.hoo.linux@gmail.com>
Reviewed-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://lore.kernel.org/r/20241128013424.4096668-49-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-11-27 17:34:15 -08:00
parent 1f66590d7f
commit 75d4642fce
1 changed files with 19 additions and 9 deletions
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28
arch/x86/kvm/cpuid.c
View File

@ -291,28 +291,38 @@ static u64 cpuid_get_supported_xcr0(struct kvm_vcpu *vcpu)
return (best->eax | ((u64)best->edx << 32)) & kvm_caps.supported_xcr0;
}
static __always_inline void kvm_update_feature_runtime(struct kvm_vcpu *vcpu,
struct kvm_cpuid_entry2 *entry,
unsigned int x86_feature,
bool has_feature)
{
cpuid_entry_change(entry, x86_feature, has_feature);
guest_cpu_cap_change(vcpu, x86_feature, has_feature);
}
void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu)
{
struct kvm_cpuid_entry2 *best;
best = kvm_find_cpuid_entry(vcpu, 1);
if (best) {
cpuid_entry_change(best, X86_FEATURE_OSXSAVE,
kvm_is_cr4_bit_set(vcpu, X86_CR4_OSXSAVE));
kvm_update_feature_runtime(vcpu, best, X86_FEATURE_OSXSAVE,
kvm_is_cr4_bit_set(vcpu, X86_CR4_OSXSAVE));
cpuid_entry_change(best, X86_FEATURE_APIC,
vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE);
kvm_update_feature_runtime(vcpu, best, X86_FEATURE_APIC,
vcpu->arch.apic_base & MSR_IA32_APICBASE_ENABLE);
if (!kvm_check_has_quirk(vcpu->kvm, KVM_X86_QUIRK_MISC_ENABLE_NO_MWAIT))
cpuid_entry_change(best, X86_FEATURE_MWAIT,
vcpu->arch.ia32_misc_enable_msr &
MSR_IA32_MISC_ENABLE_MWAIT);
kvm_update_feature_runtime(vcpu, best, X86_FEATURE_MWAIT,
vcpu->arch.ia32_misc_enable_msr &
MSR_IA32_MISC_ENABLE_MWAIT);
}
best = kvm_find_cpuid_entry_index(vcpu, 7, 0);
if (best)
cpuid_entry_change(best, X86_FEATURE_OSPKE,
kvm_is_cr4_bit_set(vcpu, X86_CR4_PKE));
kvm_update_feature_runtime(vcpu, best, X86_FEATURE_OSPKE,
kvm_is_cr4_bit_set(vcpu, X86_CR4_PKE));
best = kvm_find_cpuid_entry_index(vcpu, 0xD, 0);
if (best)