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Message-ID: <20200423132208.i522jqpevglruhur@liuwe-devbox-debian-v2.j3c5onc20sse1dnehy4noqpfcg.zx.internal.cloudapp.net>
Date: Thu, 23 Apr 2020 13:22:08 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Michael Kelley <mikelley@...rosoft.com>
Cc: kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com,
wei.liu@...nel.org, tglx@...utronix.de, mingo@...hat.com,
bp@...en8.de, x86@...nel.org, hpa@...or.com, pbonzini@...hat.com,
sean.j.christopherson@...el.com, vkuznets@...hat.com,
wanpengli@...cent.com, jmattson@...gle.com, joro@...tes.org,
kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-hyperv@...r.kernel.org
Subject: Re: [PATCH v2 0/4] Split hyperv-tlfs.h into generic and arch
specific files
On Wed, Apr 22, 2020 at 12:57:33PM -0700, Michael Kelley wrote:
> This series splits hyperv-tlfs.h into architecture independent and
> architecture specific files so that the arch independent portion can
> be shared between the x86/x64 and ARM64 code for Hyper-V. While the
> Hyper-V team has not released a version of the TLFS document that
> clearly specifies which portions of the interface are arch independent,
> we can make a fairly good assessment based on implementation work done
> to support Linux guests on Hyper-V on ARM64, and on private communication
> with the Hyper-V team. Definitions are considered arch independent if
> they are implemented by Hyper-V on both architectures (x86/x64 and ARM64),
> even if they are currently needed by Linux code only on one architecture.
>
> Many definitions in hyperv-tlfs.h have historically contained "X64" in the
> name, which doesn't make sense for architecture independent definitions.
> While many of the occurrences of "X64" have already been removed, some
> still remain in definitions that should be arch independent. The
> split removes the "X64" from the definitions so that the arch
> independent hyper-tlfs.h has no occurrences of "X64". However, to
> keep this patch set separate from a wider change in the names, aliases
> are added in the x86/x64 specific hyperv-tlfs.h so that existing code
> continues to compile. The definitions can be fixed throughout the code
> in a more incremental fashion in separate patches, and then the aliases
> can be removed.
>
> Where it is not clear if definitions are arch independent, they have been
> kept in the x86/x64 specific file. The Hyper-V team is aiming to have a
> version of the TLFS document covering ARM64 by the end of calendar 2020,
> so additional definitions may be moved into the arch independent portion
> after the new TLFS document is released.
>
> The first two patches in the series clean up the existing hyperv-tlfs.h
> file a bit by removing duplicate or unnecessary definitions so they are
> not propagated across the split. The third patch does the split, and the
> fourth patch adds new definitions that are needed on ARM64 but are generic.
>
> These changes have no functional impact.
>
> These patches are built against linux-next-20200415
Applied to hyperv-next. Thanks.
Wei.
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