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

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Message-ID: <31b189e0-503f-157d-7af0-329744ed5369@redhat.com>
Date:   Thu, 22 Oct 2020 16:06:43 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Xiaoyao Li <xiaoyao.li@...el.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 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.

Paolo