From: Avi Kivity <[email protected]>

The simplistic clts implementation has a couple of flaws:
- kvm_read_cr0_bits() is temporarily unsynchronized when vcpu->arch.cr0 changes
- if the fpu is active, we need to clear GUEST_CR0.TS, not just
  CR_READ_SHADOW.TS, so that we don't send the guest an unexpected #NM.

Fix by replacing custom logic with a call to vmx_set_cr0(), which does the
right thing, albeit less efficiently.

Signed-off-by: Avi Kivity <[email protected]>
Signed-off-by: Marcelo Tosatti <[email protected]>

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4745c7d..0fa5906 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -3002,8 +3002,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
                };
                break;
        case 2: /* clts */
-               vcpu->arch.cr0 &= ~X86_CR0_TS;
-               vmcs_writel(CR0_READ_SHADOW, kvm_read_cr0(vcpu));
+               vmx_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS));
                trace_kvm_cr_write(0, kvm_read_cr0(vcpu));
                skip_emulated_instruction(vcpu);
                vmx_fpu_activate(vcpu);
--
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