linux-kernel - Re: [PATCH v2 1/5] x86/kvm: rename HV_X64_MSR_APIC_ASSIST_PAGE to HV_X64_MSR_VP_ASSIST

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Date:   Thu, 08 Mar 2018 11:17:34 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Radim Krčmář <rkrcmar@...hat.com>
Cc:     Roman Kagan <rkagan@...tuozzo.com>, kvm@...r.kernel.org,
        x86@...nel.org, Paolo Bonzini <pbonzini@...hat.com>,
        "K. Y. Srinivasan" <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "Michael Kelley \(EOSG\)" <Michael.H.Kelley@...rosoft.com>,
        Mohammed Gamal <mmorsy@...hat.com>,
        Cathy Avery <cavery@...hat.com>, Bandan Das <bsd@...hat.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/5] x86/kvm: rename HV_X64_MSR_APIC_ASSIST_PAGE to HV_X64_MSR_VP_ASSIST_PAGE

Radim Krčmář <rkrcmar@...hat.com> writes:

> 2018-03-07 19:48+0300, Roman Kagan:
>> On Wed, Mar 07, 2018 at 05:19:44PM +0100, Radim Krčmář wrote:
>> > 2018-02-26 18:11+0100, Vitaly Kuznetsov:
>> > > diff --git a/arch/x86/include/uapi/asm/hyperv.h b/arch/x86/include/uapi/asm/hyperv.h
>> > > @@ -275,10 +275,10 @@ struct hv_tsc_emulation_status {
>> > >  #define HVCALL_POST_MESSAGE			0x005c
>> > >  #define HVCALL_SIGNAL_EVENT			0x005d
>> > >  
>> > > -#define HV_X64_MSR_APIC_ASSIST_PAGE_ENABLE		0x00000001
>> > > -#define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT	12
>> > > -#define HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_MASK	\
>> > > -		(~((1ull << HV_X64_MSR_APIC_ASSIST_PAGE_ADDRESS_SHIFT) - 1))
>> > 
>> > Removing definitions from userspace api isn't a good idea.
>> > 
>> > I have no idea why hyper.h is a userspace api, though -- Linux doesn't
>> > define any of those, so we could copy the definitions to a private
>> > header, rename, and never look at this file again.
>> 
>> That was a thinko when it was moved to uapi, and it has already been
>> identified as a problem, so now QEMU has its own header with the
>> definitions it needs, and I'm unaware of any other userspace project
>> that depends on this stuff.  So I've been planning to remove it from
>> uapi but still haven't got around to posting the patch :(
>
> Great, let's be bold here.

asm/hyperv.h is not uapi.

I would include a patch renaming arch/x86/include/uapi/asm/hyperv.h to
arch/x86/include/asm/hyperv.h but we already have 'mshyperv.h' there and
I don't quite understand the difference. We can either merge them or
come up with a rule distinguishing them.

K. Y., Michael, what do you think?

-- 
  Vitaly