KVM: SVM: Fix lazy FPU switching

If the guest writes to cr0 and leaves the TS flag at 0 while vcpu->fpu_active
is also 0, the TS flag in the guest's cr0 gets lost. This leads to corrupt FPU
state an causes Windows Vista 64bit to crash very soon after boot.  This patch
fixes this bug.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Markus Rechberger <markus.rechberger@amd.com>
Signed-off-by: Avi Kivity <avi@qumranet.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index de755cb1431d..511628916c4b 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -792,6 +792,8 @@ static void svm_set_cr0(struct kvm_vcpu *vcpu, unsigned long cr0)
         vcpu->arch.cr0 = cr0;
         cr0 |= X86_CR0_PG | X86_CR0_WP;
         cr0 &= ~(X86_CR0_CD | X86_CR0_NW);
+        if (!vcpu->fpu_active)
+                cr0 |= X86_CR0_TS;
         svm->vmcb->save.cr0 = cr0;
 }