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

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Message-ID: <CANRm+CxDBHnz1crs8_Lkb6-KRHCSwjk6bEMz3n2FwDs2ypbhQw@mail.gmail.com>
Date:   Fri, 23 Oct 2020 08:27:21 +0800
From:   Wanpeng Li <kernellwp@...il.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     LKML <linux-kernel@...r.kernel.org>, kvm <kvm@...r.kernel.org>,
        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 Thu, 22 Oct 2020 at 21:02, Paolo Bonzini <pbonzini@...hat.com> wrote:
>
> On 22/10/20 03:34, Wanpeng Li wrote:
> > From: Wanpeng Li <wanpengli@...cent.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@...gle.com>
> > Signed-off-by: Wanpeng Li <wanpengli@...cent.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.
>
> (But maybe this was discussed already; if so, please point me to the
> previous discussion).

The discussion is here. :) https://www.spinics.net/lists/kvm/msg227265.html

    Wanpeng