diff mbox

[v2,5/6] KVM/nVMX: Set the CPU_BASED_USE_MSR_BITMAPS if we have a valid L02 MSR bitmap

Message ID 1518305967-31356-6-git-send-email-dwmw@amazon.co.uk (mailing list archive)
State New, archived
Headers show

Commit Message

Woodhouse, David Feb. 10, 2018, 11:39 p.m. UTC 
From: KarimAllah Ahmed <karahmed@amazon.de>

We either clear the CPU_BASED_USE_MSR_BITMAPS and end up intercepting all
MSR accesses or create a valid L02 MSR bitmap and use that. This decision
has to be made every time we evaluate whether we are going to generate the
L02 MSR bitmap.

Before commit 086e7d4118cc ("KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL")
this was probably OK since the decision was always identical. This is no
longer the case now since the MSR bitmap might actually change once we
decide to not intercept SPEC_CTRL and PRED_CMD.

Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de>
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---
 arch/x86/kvm/vmx.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

Comments

Ingo Molnar Feb. 11, 2018, 10:19 a.m. UTC | #1 
* David Woodhouse <dwmw@amazon.co.uk> wrote:

> From: KarimAllah Ahmed <karahmed@amazon.de>
> 
> We either clear the CPU_BASED_USE_MSR_BITMAPS and end up intercepting all
> MSR accesses or create a valid L02 MSR bitmap and use that. This decision
> has to be made every time we evaluate whether we are going to generate the
> L02 MSR bitmap.
> 
> Before commit 086e7d4118cc ("KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL")
> this was probably OK since the decision was always identical. This is no
> longer the case now since the MSR bitmap might actually change once we
> decide to not intercept SPEC_CTRL and PRED_CMD.

Note, I fixed the changelog to refer to the correct upstream SHA1, which is:

  d28b387fb74d: KVM/VMX: Allow direct access to MSR_IA32_SPEC_CTRL

Thanks,

	Ingo
Ingo Molnar Feb. 11, 2018, 10:55 a.m. UTC | #2 
* Woodhouse, David <dwmw@amazon.co.uk> wrote:

> On Sun, 2018-02-11 at 11:19 +0100, Ingo Molnar wrote:
> > Note, I fixed the changelog to refer to the correct upstream SHA1,
> > which is:
> > 
> >   d28b387fb74d: KVM/VMX: Allow direct access to MSR_IA32_SPEC_CTRL
> 
> Thanks for catching that.
> 
> Wouldn't it be nice if 'git rebase --interactive tip/x86/pti' had done
> that *for* me? :)

Yeah, but given that the commit title changed as well:

   086e7d4118cc ("KVM: VMX: Allow direct access to MSR_IA32_SPEC_CTRL")
   d28b387fb74d ("KVM/VMX: Allow direct access to MSR_IA32_SPEC_CTRL")

I'd rather not have tooling guess about such things.

Thanks,

	Ingo
diff mbox

Patch

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 599179b..91e3539 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -10130,7 +10130,8 @@  static void nested_get_vmcs12_pages(struct kvm_vcpu *vcpu,
 	if (cpu_has_vmx_msr_bitmap() &&
 	    nested_cpu_has(vmcs12, CPU_BASED_USE_MSR_BITMAPS) &&
 	    nested_vmx_merge_msr_bitmap(vcpu, vmcs12))
-		;
+		vmcs_set_bits(CPU_BASED_VM_EXEC_CONTROL,
+			      CPU_BASED_USE_MSR_BITMAPS);
 	else
 		vmcs_clear_bits(CPU_BASED_VM_EXEC_CONTROL,
 				CPU_BASED_USE_MSR_BITMAPS);