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From:   Jim Mattson <jmattson@google.com>
Date:   Thu, 22 Oct 2020 09:35:03 -0700
Message-ID: <CALMp9eR3Ng-WBrumXaJAecLWZECf-1NfzW+eTA0VxWuAcKAjAA@mail.gmail.com>
Subject: Re: [PATCH] KVM: X86: Expose KVM_HINTS_REALTIME in KVM_GET_SUPPORTED_CPUID
To:     Paolo Bonzini <pbonzini@redhat.com>
Cc:     Wanpeng Li <kernellwp@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        kvm list <kvm@vger.kernel.org>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Wanpeng Li <wanpengli@tencent.com>,
        Joerg Roedel <joro@8bytes.org>
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On Thu, Oct 22, 2020 at 6:02 AM Paolo Bonzini <pbonzini@redhat.com> wrote:
>
> On 22/10/20 03:34, Wanpeng Li wrote:
> > From: Wanpeng Li <wanpengli@tencent.com>
> >
> > Per KVM_GET_SUPPORTED_CPUID ioctl documentation:
> >
> > This ioctl returns x86 cpuid features which are supported by both the
> > hardware and kvm in its default configuration.
> >
> > A well-behaved userspace should not set the bit if it is not supported.
> >
> > Suggested-by: Jim Mattson <jmattson@google.com>
> > Signed-off-by: Wanpeng Li <wanpengli@tencent.com>
>
> 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.

That is not how the API is defined, but I'm sure you know that. :-)

> (But maybe this was discussed already; if so, please point me to the
> previous discussion).
>
> Paolo