linux-kernel - Re: [PATCH] KVM: X86: Expose KVM_HINTS_REALTIME in KVM_GET_SUPPORTED

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Message-ID: <18e7a0c6-faff-8c4c-0830-a0bc02627a36@intel.com>
Date:   Thu, 22 Oct 2020 22:28:01 +0800
From:   Xiaoyao Li <xiaoyao.li@...el.com>
To:     Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <kernellwp@...il.com>, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org
Cc:     Sean Christopherson <sean.j.christopherson@...el.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>
Subject: Re: [PATCH] KVM: X86: Expose KVM_HINTS_REALTIME in
 KVM_GET_SUPPORTED_CPUID

On 10/22/2020 10:06 PM, Paolo Bonzini wrote:
> On 22/10/20 15:31, Xiaoyao Li wrote:
>>>
>>> It's common for userspace to copy all supported CPUID bits to
>>> KVM_SET_CPUID2, I don't think this is the right behavior for
>>> KVM_HINTS_REALTIME.
>>
>> It reminds of X86_FEATURE_WAITPKG, which is added to supported CPUID
>> recently as a fix but QEMU exposes it to guest only when "-overcommit
>> cpu-pm"
> 
> WAITPKG is not included in KVM_GET_SUPPORTED_CPUID either.  QEMU detects
> it through the MSR_IA32_UMWAIT register.

Doesn't 0abcc8f65cc2 ("KVM: VMX: enable X86_FEATURE_WAITPKG in KVM 
capabilities") add WAITPKG to KVM_GET_SUPPORTED_CPUID?

> Paolo
>