Re: [PATCH 1/7] KVM: nVMX: Use kvm_set_msr to load IA32_PERF_GLOBAL_CTRL on vmexit

[Oliver Upton <oupton@google.com>]

On Wed, Aug 28, 2019 at 06:30:29PM -0700, Krish Sadhukhan wrote:
> 
> 
> On 08/28/2019 04:41 PM, Oliver Upton wrote:
> > The existing implementation for loading the IA32_PERF_GLOBAL_CTRL MSR
> > on VM-exit was incorrect, as the next call to atomic_switch_perf_msrs()
> > could cause this value to be overwritten. Instead, call kvm_set_msr()
> > which will allow atomic_switch_perf_msrs() to correctly set the values.
> > 
> > Suggested-by: Jim Mattson <jmattson@google.com>
> > Signed-off-by: Oliver Upton <oupton@google.com>
> > ---
> >   arch/x86/kvm/vmx/nested.c | 13 ++++++++++---
> >   1 file changed, 10 insertions(+), 3 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> > index ced9fba32598..b0ca34bf4d21 100644
> > --- a/arch/x86/kvm/vmx/nested.c
> > +++ b/arch/x86/kvm/vmx/nested.c
> > @@ -3724,6 +3724,7 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
> >   				   struct vmcs12 *vmcs12)
> >   {
> >   	struct kvm_segment seg;
> > +	struct msr_data msr_info;
> >   	u32 entry_failure_code;
> >   	if (vmcs12->vm_exit_controls & VM_EXIT_LOAD_IA32_EFER)
> > @@ -3800,9 +3801,15 @@ static void load_vmcs12_host_state(struct kvm_vcpu *vcpu,
> >   		vmcs_write64(GUEST_IA32_PAT, vmcs12->host_ia32_pat);
> >   		vcpu->arch.pat = vmcs12->host_ia32_pat;
> >   	}
> > -	if (vmcs12->vm_exit_controls & VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL)
> > -		vmcs_write64(GUEST_IA32_PERF_GLOBAL_CTRL,
> > -			vmcs12->host_ia32_perf_global_ctrl);
> > +	if (vmcs12->vm_exit_controls & VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL) {
> > +		msr_info.host_initiated = false;
> > +		msr_info.index = MSR_CORE_PERF_GLOBAL_CTRL;
> > +		msr_info.data = vmcs12->host_ia32_perf_global_ctrl;
> > +		if (kvm_set_msr(vcpu, &msr_info))
> > +			pr_debug_ratelimited(
> > +				"%s cannot write MSR (0x%x, 0x%llx)\n",
> > +				__func__, msr_info.index, msr_info.data);
> > +	}
> >   	/* Set L1 segment info according to Intel SDM
> >   	    27.5.2 Loading Host Segment and Descriptor-Table Registers */
> 
> These patches are what I am already working on. I sent the following:
> 
>         [KVM nVMX]: Check "load IA32_PERF_GLOBAL_CTRL" on vmentry of nested
> guests
>         [PATCH 0/4][kvm-unit-test nVMX]: Test "load
> IA32_PERF_GLOBAL_CONTROL" VM-entry control on vmentry of nested guests
> 
> a few months back. I got feedback from the alias and am working on v2 which
> I will send soon...
>
Yes, I saw your previous mail for this feature. I started work on this
because of a need for this feature + mentioned you in the cover letter.
However, it would be better to give codeveloper credit with your
permission.

May I resend this patchset with a 'Co-Developed-by' tag crediting you?