Re: [PATCH 4/7] KVM: nVMX: check GUEST_IA32_PERF_GLOBAL_CTRL on VM-Entry

[Oliver Upton <oupton@google.com>]

On Fri, Aug 30, 2019 at 11:37:03AM -0700, Sean Christopherson wrote:
> On Wed, Aug 28, 2019 at 04:41:31PM -0700, Oliver Upton wrote:
> > According to the SDM 26.3.1.1, "If the "load IA32_PERF_GLOBAL_CTRL" VM-entry
> > control is 1, bits reserved in the IA32_PERF_GLOBAL_CTRL MSR must be 0 in the
> > field for that register".
> > 
> > Adding condition to nested_vmx_check_guest_state() to check the validity of
> > GUEST_IA32_PERF_GLOBAL_CTRL if the "load IA32_PERF_GLOBAL_CTRL" bit is
> > set on the VM-entry control.
> 
> Same comment on mood.  And for this case, it's probably overkill to
> give a play-by-play of the code, just state that you're adding a check
> as described in the SDM, e.g.:
> 
> Add a nested VM-Enter consistency check when loading the guest's
> IA32_PERF_GLOBAL_CTRL MSR from vmcs12.  Per Intel's SDM:
> 
>   If the "load IA32_PERF_GLOBAL_CTRL" VM-entry control is 1, bits
>   reserved in the IA32_PERF_GLOBAL_CTRL MSR must be 0 in the field for
>   that register.

Ack. This is a style problem throughout, I will make sure to address in
the next set I send out. Thanks for the suggested text as well, reads a
lot better than what I had before!
> > 
> > Suggested-by: Jim Mattson <jmattson@google.com>
> > Signed-off-by: Oliver Upton <oupton@google.com>
> > ---
> >  arch/x86/kvm/vmx/nested.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> > index 9ba90b38d74b..8d6f0144b1bd 100644
> > --- a/arch/x86/kvm/vmx/nested.c
> > +++ b/arch/x86/kvm/vmx/nested.c
> > @@ -10,6 +10,7 @@
> >  #include "hyperv.h"
> >  #include "mmu.h"
> >  #include "nested.h"
> > +#include "pmu.h"
> >  #include "trace.h"
> >  #include "x86.h"
> >  
> > @@ -2748,6 +2749,11 @@ static int nested_vmx_check_guest_state(struct kvm_vcpu *vcpu,
> >  		return -EINVAL;
> >  	}
> >  
> > +	if (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL &&
> > +	    !kvm_is_valid_perf_global_ctrl(vcpu,
> > +					   vmcs12->guest_ia32_perf_global_ctrl))
> > +		return -EINVAL;
> > +
> >  	/*
> >  	 * If the load IA32_EFER VM-entry control is 1, the following checks
> >  	 * are performed on the field for the IA32_EFER MSR:
> > -- 
> > 2.23.0.187.g17f5b7556c-goog
> >