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

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On 8/29/19 1:07 AM, Oliver Upton wrote:
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@xxxxxxxxxx>
Signed-off-by: Oliver Upton <oupton@xxxxxxxxxx>
---
    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?
Absolutely. Thanks !



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