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 [thread overview]
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 ?
next prev parent reply other threads:[~2019-08-23 5:30 UTC|newest]
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" on vmentry of nested guests 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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