Commit 1b385cbd authored Feb 27, 2014 by Paolo Bonzini

kvm, vmx: Really fix lazy FPU on nested guest



Commit e504c909 (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: e504c909
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>

parent a08d3b3b

arch/x86/kvm/vmx.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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));

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