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Subject[PATCH] kvm, vmx: Really fix lazy FPU on nested guest
Date
Commit e504c9098ed6 (kvm, vmx: Fix lazy FPU on nested guest, 2013-11-13)
highlighted a real problem, but the fix was subtly wrong.

nested_read_cr0 is the CR0 as read by L2, but here we want to look at
the CR0 value reflecting L1's setup. In other words, L2 might think
that TS=0 (so nested_read_cr0 has the bit clear); but if L1 is actually
running it with TS=1, we should inject the fault into L1.

The effective value of CR0 in L2 is contained in vmcs12->guest_cr0, use
it.

Fixes: e504c9098ed6acd9e1079c5e10e4910724ad429f
Reported-by: Kashyap Chamarty <kchamart@redhat.com>
Reported-by: Stefan Bader <stefan.bader@canonical.com>
Tested-by: Kashyap Chamarty <kchamart@redhat.com>
Tested-by: Anthoine Bourgeois <bourgeois@bertin.fr>
Cc: stable@vger.kernel.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/kvm/vmx.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index a06f101ef64b..392752834751 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -6688,7 +6688,7 @@ static bool nested_vmx_exit_handled(struct kvm_vcpu *vcpu)
else if (is_page_fault(intr_info))
return enable_ept;
else if (is_no_device(intr_info) &&
- !(nested_read_cr0(vmcs12) & X86_CR0_TS))
+ !(vmcs12->guest_cr0 & X86_CR0_TS))
return 0;
return vmcs12->exception_bitmap &
(1u << (intr_info & INTR_INFO_VECTOR_MASK));
--
1.8.3.1


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