linux-kernel - Re: [PATCH] x86/acrn: Improve ACRN hypercalls

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Message-ID: <6c516a7c-ac97-e0b1-b056-06a17d1b7420@intel.com>
Date:   Thu, 4 Aug 2022 12:03:56 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     Uros Bizjak <ubizjak@...il.com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86/acrn: Improve ACRN hypercalls

On 8/4/22 11:56, Uros Bizjak wrote:
> The %r8 is not preserved across function calls, so your statement
> above is correct. But as long as there is no function call *between*
> the variable definition and the assembly, the approach with the local
> register variable works without any problems. It is even something GCC
> itself has used in its library for years.

I'm glad it's workout out for GCC.  But, the kernel is not GCC.  I
specifically asked for the ACRN code to be the way that it is today and
your argument is not making me reconsider it in the slightest.

So, thanks for the patch, but I don't think we should apply it.