linux-kernel - Re: [PATCH v2 10/15] KVM: x86/vmx: Check Arch LBR config when return perf capabilities

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Date:   Sun, 25 Dec 2022 12:28:25 +0800
From:   "Yang, Weijiang" <weijiang.yang@...el.com>
To:     Like Xu <like.xu.linux@...il.com>
CC:     <kan.liang@...ux.intel.com>, <wei.w.wang@...el.com>,
        <seanjc@...gle.com>, <pbonzini@...hat.com>, <jmattson@...gle.com>,
        <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 10/15] KVM: x86/vmx: Check Arch LBR config when return
 perf capabilities


On 12/22/2022 7:06 PM, Like Xu wrote:
> On 25/11/2022 12:05 pm, Yang Weijiang wrote:
>> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
>> index b28be793de29..59bdd9873fb5 100644
>> --- a/arch/x86/kvm/vmx/nested.c
>> +++ b/arch/x86/kvm/vmx/nested.c
>> @@ -2360,6 +2360,10 @@ static void prepare_vmcs02_early(struct 
>> vcpu_vmx *vmx, struct loaded_vmcs *vmcs0
>>           if (guest_efer != host_efer)
>>               exec_control |= VM_ENTRY_LOAD_IA32_EFER;
>>       }
>> +
>> +    if (cpu_has_vmx_arch_lbr())
>> +        exec_control &= ~VM_ENTRY_LOAD_IA32_LBR_CTL;
>
> Please verify that (arch) lbr is not available in the nested test case.
> Thus when we support nested lbr, the developer will be aware of the 
> need for test case updates


It's not available in either KUT or selftest cases now.



>
>> +
>>       vm_entry_controls_set(vmx, exec_control);
>>         /*