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authorPaolo Bonzini <pbonzini@redhat.com>2013-10-02 16:06:15 +0200
committerGleb Natapov <gleb@redhat.com>2013-10-03 12:29:07 +0300
commitd7876f1be40a16223a44355740de625849504eb5 (patch)
tree33e0f69e36fd042139eb490745515c466a1685d2 /arch/x86/kvm
parent647e23bb333ff196e7be8ae08c842d855fb850f6 (diff)
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 <pbonzini@redhat.com> Signed-off-by: Gleb Natapov <gleb@redhat.com>
Diffstat (limited to 'arch/x86/kvm')
-rw-r--r--arch/x86/kvm/cpuid.c8
-rw-r--r--arch/x86/kvm/x86.c18
2 files changed, 23 insertions, 3 deletions
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index a03a9faf81b..5a5ff94fef6 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 187f824b145..7d5c5207a41 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);