linux-kernel - Re: [PATCH 01/15] hyperv-tlfs: Change shared HV_REGISTER_* defines to HV_MSR

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Message-ID: <ZMsCDk68qo3WDcUo@liuwe-devbox-debian-v2>
Date:   Thu, 3 Aug 2023 01:25:34 +0000
From:   Wei Liu <wei.liu@...nel.org>
To:     Nuno Das Neves <nunodasneves@...ux.microsoft.com>
Cc:     linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        x86@...nel.org, linux-arm-kernel@...ts.infradead.org,
        linux-arch@...r.kernel.org, mikelley@...rosoft.com,
        kys@...rosoft.com, wei.liu@...nel.org, haiyangz@...rosoft.com,
        decui@...rosoft.com, ssengar@...ux.microsoft.com,
        mukeshrathor@...rosoft.com, stanislav.kinsburskiy@...il.com,
        jinankjain@...ux.microsoft.com, apais@...ux.microsoft.com,
        Tianyu.Lan@...rosoft.com, vkuznets@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, will@...nel.org, catalin.marinas@....com
Subject: Re: [PATCH 01/15] hyperv-tlfs: Change shared HV_REGISTER_* defines
 to HV_MSR_*

On Thu, Jul 27, 2023 at 12:54:36PM -0700, Nuno Das Neves wrote:
> In x86 hyperv-tlfs, HV_REGISTER_ prefix is used to indicate MSRs
> accessed via rdmsrl/wrmsrl. But in ARM64, HV_REGISTER_ instead indicates
> VP registers accessed via get/set vp registers hypercall.
> 
> This is due to HV_REGISTER_* names being used by hv_set/get_register,
> with the arch-specific version delegating to the appropriate mechanism.
> 
> The problem is, using prefix HV_REGISTER_ for MSRs will conflict with
> VP registers when they are introduced for x86 in future.
> 
> This patch solves the issue by:
> 
> 1. Defining all the x86 MSRs with a consistent prefix: HV_X64_MSR_.
>    This is so HV_REGISTER_ can be reserved for VP registers.
> 
> 2. Change the non-arch-specific alias used by hv_set/get_register to
>    HV_MSR_. This is also happens to be the same name HyperV uses for this
>    purpose.
> 
> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>

Assuming the prior (private?) discussion with Michael led to this patch:

Acked-by: Wei Liu <wei.liu@...nel.org>