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From: Krish Sadhukhan <krish.sadhukhan@oracle.com>
To: Jim Mattson <jmattson@google.com>
Cc: "kvm list" <kvm@vger.kernel.org>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [PATCH 6/8][KVM nVMX]: Load IA32_PERF_GLOBAL_CTRL MSR on vmentry of nested guests
Date: Thu, 22 Aug 2019 22:29:36 -0700
Message-ID: <a2889868-eb62-5843-f3d2-fe066055e80c@oracle.com> (raw)
In-Reply-To: <CALMp9eR8u6qPF5Gv-UEXSmB9NX=H=AGb4jh4d=mEm7jyTqBfWg@mail.gmail.com>


On 8/15/19 3:44 PM, Jim Mattson wrote:
> On Wed, Apr 24, 2019 at 4:43 PM Krish Sadhukhan
> <krish.sadhukhan@oracle.com> wrote:
>> According to section "Loading Guest State" in Intel SDM vol 3C, the
>> IA32_PERF_GLOBAL_CTRL MSR is loaded on vmentry of nested guests:
>>
>>      "If the “load IA32_PERF_GLOBAL_CTRL” VM-entry control is 1, the
>>       IA32_PERF_GLOBAL_CTRL MSR is loaded from the IA32_PERF_GLOBAL_CTRL
>>       field."
>>
>> Signed-off-by: Krish Sadhukhan <krish.sadhukhan@oracle.com>
>> Suggested-by: Jim Mattson <jmattson@google.com>
>> Reviewed-by: Karl Heubaum <karl.heubaum@oracle.com>
>> ---
>>   arch/x86/kvm/vmx/nested.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
>> index a7bf19eaa70b..8177374886a9 100644
>> --- a/arch/x86/kvm/vmx/nested.c
>> +++ b/arch/x86/kvm/vmx/nested.c
>> @@ -2300,6 +2300,10 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
>>          vcpu->arch.cr0_guest_owned_bits &= ~vmcs12->cr0_guest_host_mask;
>>          vmcs_writel(CR0_GUEST_HOST_MASK, ~vcpu->arch.cr0_guest_owned_bits);
>>
>> +       if (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PERF_GLOBAL_CTRL)
>> +               vmcs_write64(GUEST_IA32_PERF_GLOBAL_CTRL,
>> +                            vmcs12->guest_ia32_perf_global_ctrl);
>> +
>>          if (vmx->nested.nested_run_pending &&
>>              (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_IA32_PAT)) {
>>                  vmcs_write64(GUEST_IA32_PAT, vmcs12->guest_ia32_pat);
>> --
>> 2.17.2
>>
> This isn't quite right. The GUEST_IA32_PERF_GLOBAL_CTRL value is just
> going to get overwritten later by atomic_switch_perf_msrs().
>
> Instead of writing the vmcs12 value directly into the vmcs02, you
> should call kvm_set_msr(), exactly as it would have been called if
> MSR_CORE_PERF_GLOBAL_CTRL had been in the vmcs12
> VM-entry MSR-load list. Then, atomic_switch_perf_msrs() will
> automatically do the right thing.


I notice that the existing code for VM_EXIT_LOAD_IA32_PERF_GLOBAL_CTRL 
in load_vmcs12_host_state() doesn't use kvm_set_msr():

             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);

This should also be changed to use kvm_set_msr() then ?


  parent reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-04-24 23:17 [KVM nVMX]: Check "load IA32_PERF_GLOBAL_CTRL" " Krish Sadhukhan
2019-04-24 23:17 ` [PATCH 1/8][KVMnVMX]: Enable "load IA32_PERF_GLOBAL_CTRL" VM-exit control for " Krish Sadhukhan
2019-05-13 18:49   ` Sean Christopherson
2019-05-13 22:08     ` Krish Sadhukhan
2019-04-24 23:17 ` [PATCH 2/8][KVM nVMX]: Enable "load IA32_PERF_GLOBAL_CTRL" VM-entry " Krish Sadhukhan
2019-05-13 18:49   ` Sean Christopherson
2019-04-24 23:17 ` [PATCH 3/8][KVM VMX]: Add a function to check reserved bits in MSR_CORE_PERF_GLOBAL_CTRL Krish Sadhukhan
2019-05-13 18:57   ` Sean Christopherson
2019-08-15 22:29     ` Jim Mattson
2019-04-24 23:17 ` [PATCH 4/8][KVM nVMX]: Check "load IA32_PERF_GLOBAL_CTRL" VM-exit control on vmentry of nested guests Krish Sadhukhan
2019-05-13 19:00   ` Sean Christopherson
2019-05-16 22:07     ` Krish Sadhukhan
2019-05-17 20:34       ` Sean Christopherson
2019-08-15 22:54         ` Jim Mattson
2019-04-24 23:17 ` [PATCH 5/8][KVM nVMX]: Check "load IA32_PERF_GLOBAL_CTRL" VM-entry " Krish Sadhukhan
2019-08-15 22:36   ` Jim Mattson
2019-04-24 23:17 ` [PATCH 6/8][KVM nVMX]: Load IA32_PERF_GLOBAL_CTRL MSR " Krish Sadhukhan
2019-08-15 22:44   ` Jim Mattson
2019-08-21 23:05     ` Krish Sadhukhan
2019-08-21 23:10       ` Jim Mattson
2019-08-23  5:29     ` Krish Sadhukhan [this message]
2019-08-23 15:57       ` Jim Mattson
2019-04-24 23:17 ` [PATCH 7/8][KVM nVMX]: Enable "load IA32_PERF_GLOBAL_CTRL VM-{entry,exit} controls Krish Sadhukhan
2019-05-13 19:12   ` Sean Christopherson
2019-08-15 23:02     ` Jim Mattson
2019-04-24 23:17 ` [PATCH 8/8][KVM nVMX]: Test "load IA32_PERF_GLOBAL_CTRL" controls on vmentry of nested guests Krish Sadhukhan
2019-05-13 18:46 ` [KVM nVMX]: Check "load IA32_PERF_GLOBAL_CTRL" " Sean Christopherson

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