linux-kernel - Re: [PATCH v3 06/21] KVM:x86: Report XSS as to-be-saved if there are supported features

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Message-ID: <90eb3d2c-f692-b6d4-d1ba-2e63b4d11936@intel.com>
Date:   Wed, 24 May 2023 16:19:29 +0800
From:   "Yang, Weijiang" <weijiang.yang@...el.com>
To:     Chao Gao <chao.gao@...el.com>
CC:     <seanjc@...gle.com>, <pbonzini@...hat.com>, <kvm@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <peterz@...radead.org>,
        <rppt@...nel.org>, <binbin.wu@...ux.intel.com>,
        <rick.p.edgecombe@...el.com>, <john.allen@....com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [PATCH v3 06/21] KVM:x86: Report XSS as to-be-saved if there are
 supported features


On 5/24/2023 3:06 PM, Chao Gao wrote:
> On Thu, May 11, 2023 at 12:08:42AM -0400, Yang Weijiang wrote:
>> From: Sean Christopherson <sean.j.christopherson@...el.com>
>>
>> Add MSR_IA32_XSS to the list of MSRs reported to userspace if
>> supported_xss is non-zero, i.e. KVM supports at least one XSS based
>> feature.
> The changelog doesn't match what the patch does.
>
> Do you need to check if supported_xss is non-zero in kvm_probe_msr_to_save(),
> e.g.,
>          case MSR_IA32_XSS:
>                  if (!kvm_caps.supported_xss)
>                          return;
>                  break;

I looked back the history of this patch, there's similar check 
originally, however it's lost

during following rebases. I'll add it back. Thanks for pointing it out!

>> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
>> Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
>> ---
>> arch/x86/kvm/x86.c | 1 +
>> 1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
>> index e7f78fe79b32..33a780fe820b 100644
>> --- a/arch/x86/kvm/x86.c
>> +++ b/arch/x86/kvm/x86.c
>> @@ -1454,6 +1454,7 @@ static const u32 msrs_to_save_base[] = {
>> 	MSR_IA32_UMWAIT_CONTROL,
>>
>> 	MSR_IA32_XFD, MSR_IA32_XFD_ERR,
>> +	MSR_IA32_XSS,
>> };
>>
>> static const u32 msrs_to_save_pmu[] = {
>> -- 
>> 2.27.0
>>