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

[Oliver Upton <oupton@google.com>]

On Thu, Aug 29, 2019 at 12:19:21AM -0700, Krish Sadhukhan wrote:
> 
> On 8/28/19 7:02 PM, Oliver Upton wrote:
> > 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
> I understand. I know that I have been bit late on this...
No worries here! Glad I had a good starting point to go from :-)
> > + 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?
> 
> Sure. Thank you !

One last thing, need a Signed-off-by tag corresponding to this. Do I
have your permission to do so in the resend?