From d7876f1be40a16223a44355740de625849504eb5 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 2 Oct 2013 16:06:15 +0200 Subject: [PATCH] KVM: x86: prevent setting unsupported XSAVE states A guest can still attempt to save and restore XSAVE states even if they have been masked in CPUID leaf 0Dh. This usually is not visible to the guest, but is still wrong: "Any attempt to set a reserved bit (as determined by the contents of EAX and EDX after executing CPUID with EAX=0DH, ECX= 0H) in XCR0 for a given processor will result in a #GP exception". The patch also performs the same checks as __kvm_set_xcr in KVM_SET_XSAVE. This catches migration from newer to older kernel/processor before the guest starts running. Signed-off-by: Paolo Bonzini Signed-off-by: Gleb Natapov --- arch/x86/include/asm/kvm_host.h | 1 + arch/x86/kvm/cpuid.c | 8 ++++++++ arch/x86/kvm/x86.c | 18 +++++++++++++++--- 3 files changed, 24 insertions(+), 3 deletions(-) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index c76ff74a98f2..35d10d1a6b58 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -389,6 +389,7 @@ struct kvm_vcpu_arch { struct fpu guest_fpu; u64 xcr0; + u64 guest_supported_xcr0; struct kvm_pio_request pio; void *pio_data; diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c index a03a9faf81b0..5a5ff94fef65 100644 --- a/arch/x86/kvm/cpuid.c +++ b/arch/x86/kvm/cpuid.c @@ -46,6 +46,14 @@ void kvm_update_cpuid(struct kvm_vcpu *vcpu) apic->lapic_timer.timer_mode_mask = 1 << 17; } + 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)) & + host_xcr0 & KVM_SUPPORTED_XCR0; + kvm_pmu_cpuid_update(vcpu); } diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 187f824b1454..7d5c5207a414 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -586,7 +586,7 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr) return 1; if ((xcr0 & XSTATE_YMM) && !(xcr0 & XSTATE_SSE)) return 1; - if (xcr0 & ~host_xcr0) + if (xcr0 & ~vcpu->arch.guest_supported_xcr0) return 1; kvm_put_guest_xcr0(vcpu); vcpu->arch.xcr0 = xcr0; @@ -3003,10 +3003,19 @@ static int kvm_vcpu_ioctl_x86_set_xsave(struct kvm_vcpu *vcpu, u64 xstate_bv = *(u64 *)&guest_xsave->region[XSAVE_HDR_OFFSET / sizeof(u32)]; - if (cpu_has_xsave) + if (cpu_has_xsave) { + /* + * Here we allow setting states that are not present in + * CPUID leaf 0xD, index 0, EDX:EAX. This is for compatibility + * with old userspace. + */ + if (xstate_bv & ~KVM_SUPPORTED_XCR0) + return -EINVAL; + if (xstate_bv & ~host_xcr0) + return -EINVAL; memcpy(&vcpu->arch.guest_fpu.state->xsave, guest_xsave->region, xstate_size); - else { + } else { if (xstate_bv & ~XSTATE_FPSSE) return -EINVAL; memcpy(&vcpu->arch.guest_fpu.state->fxsave, @@ -6940,6 +6949,9 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu) vcpu->arch.ia32_tsc_adjust_msr = 0x0; vcpu->arch.pv_time_enabled = false; + + vcpu->arch.guest_supported_xcr0 = 0; + kvm_async_pf_hash_reset(vcpu); kvm_pmu_init(vcpu);