Statically enable all xfeatures allowed by guest perm in KVM_SET_CPUID2, with fpstate buffer sized accordingly. This avoids run-time expansion in the emulation and restore path of XCR0 and XFD MSR [1]. Change kvm_vcpu_after_set_cpuid() to return error given fpstate reallocation may fail. [1] https://lore.kernel.org/all/20211214024948.048572883@xxxxxxxxxxxxx/ Suggested-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Suggested-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> Signed-off-by: Jing Liu <jing2.liu@xxxxxxxxx> --- arch/x86/kvm/cpuid.c | 24 +++++++++++++++++------- 1 file changed, 17 insertions(+), 7 deletions(-) diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index a068373a7fbd..eb5a5070accb 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -204,10 +204,12 @@ void kvm_update_cpuid_runtime(struct kvm_vcpu *vcpu) } EXPORT_SYMBOL_GPL(kvm_update_cpuid_runtime); -static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) +static int kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) { struct kvm_lapic *apic = vcpu->arch.apic; struct kvm_cpuid_entry2 *best; + u64 xfeatures; + int r; best = kvm_find_cpuid_entry(vcpu, 1, 0); if (best && apic) { @@ -222,9 +224,17 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) best = kvm_find_cpuid_entry(vcpu, 0xD, 0); if (!best) vcpu->arch.guest_supported_xcr0 = 0; - else - vcpu->arch.guest_supported_xcr0 = - (best->eax | ((u64)best->edx << 32)) & supported_xcr0; + else { + xfeatures = best->eax | ((u64)best->edx << 32); + + vcpu->arch.guest_supported_xcr0 = xfeatures & supported_xcr0; + + if (xfeatures != vcpu->arch.guest_fpu.xfeatures) { + r = fpu_update_guest_perm_features(&vcpu->arch.guest_fpu); + if (r) + return r; + } + } /* * Bits 127:0 of the allowed SECS.ATTRIBUTES (CPUID.0x12.0x1) enumerate @@ -260,6 +270,8 @@ static void kvm_vcpu_after_set_cpuid(struct kvm_vcpu *vcpu) * adjustments to the reserved GPA bits. */ kvm_mmu_after_set_cpuid(vcpu); + + return 0; } int cpuid_query_maxphyaddr(struct kvm_vcpu *vcpu) @@ -301,9 +313,7 @@ static int kvm_set_cpuid(struct kvm_vcpu *vcpu, struct kvm_cpuid_entry2 *e2, kvm_update_kvm_cpuid_base(vcpu); kvm_update_cpuid_runtime(vcpu); - kvm_vcpu_after_set_cpuid(vcpu); - - return 0; + return kvm_vcpu_after_set_cpuid(vcpu); } /* when an old userspace process fills a new kernel module */ -- 2.27.0
