Re: [PATCH 3/3] X86/nVMX: Update the MSR_BITMAP field with the L02 MSR BITMAP

[KarimAllah Ahmed]

On 02/10/2018 12:26 AM, Jim Mattson wrote:
> On Thu, Feb 8, 2018 at 2:53 PM, KarimAllah Ahmed <karahmed@xxxxxxxxx> wrote:
> > ... otherwise we will just be running with the L1 MSR BITMAP!
> >
> > It does not seem that we ever update the MSR_BITMAP when the nested guest
> > is running. The only place where we update the MSR_BITMAP field in VMCS is
> > for the L1 guest!
> >
> > Signed-off-by: KarimAllah Ahmed <karahmed@xxxxxxxxx>
> > Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
> > Cc: Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx>
> > Cc: kvm@xxxxxxxxxxxxxxx
> > Cc: linux-kernel@xxxxxxxxxxxxxxx
> > ---
> >   arch/x86/kvm/vmx.c | 3 +++
> >   1 file changed, 3 insertions(+)
> >
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index 91e3539..f40be10 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -10589,6 +10589,9 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
> >          vmcs_writel(GUEST_GDTR_BASE, vmcs12->guest_gdtr_base);
> >          vmcs_writel(GUEST_IDTR_BASE, vmcs12->guest_idtr_base);
> >
> > +       if (cpu_has_vmx_msr_bitmap())
> > +               vmcs_write64(MSR_BITMAP, __pa(vmx->nested.vmcs02.msr_bitmap));
> > +
>
> This is already in David's "[PATCH 5/9] KVM: VMX: make MSR bitmaps
> per-VCPU," isn't it?

I assume you are referring to this:

https://patchwork.kernel.org/patch/10194819/

.. which is now:

commit 904e14fb7cb9 ("KVM: VMX: make MSR bitmaps per-VCPU")

right?

If this is the case, then I do not see where the MSR_BITMAP is being
updated here. In fact, would not this be the commit that actually broke
it?

Now MSR_BITMAP is only set in vmx_vcpu_setup:

        if (cpu_has_vmx_msr_bitmap())
                vmcs_write64(MSR_BITMAP, __pa(vmx->vmcs01.msr_bitmap));

> >          if (from_vmentry &&
> >              (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS)) {
> >                  kvm_set_dr(vcpu, 7, vmcs12->guest_dr7);
> > --
> > 2.7.4
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