linux-kernel - Re: [RFC PATCH v5 4/4] x86/acrn: Add hypercall for ACRN guest

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Date:   Mon, 29 Apr 2019 09:36:25 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Zhao, Yakui" <yakui.zhao@...el.com>
Cc:     Ingo Molnar <mingo@...nel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "Chen, Jason CJ" <jason.cj.chen@...el.com>
Subject: Re: [RFC PATCH v5 4/4] x86/acrn: Add hypercall for ACRN guest

On Mon, Apr 29, 2019 at 09:24:12AM +0800, Zhao, Yakui wrote:
> Yes. "movq" only indicates explicitly that it is 64-bit mov as ACRN guest
> only works under 64-bit mode.
> I also check the usage of "mov" and "movq" in this scenario. There is no
> difference except that the movq is an explicit 64-op.

Damn, I'm tired of explaining this: it is explicit only to the code
reader. gcc generates the *same* instruction no matter whether it has a
"q" suffix or not as long as the destination register is a 64-bit one.

If you prefer to have it explicit, sure, use "movq".

-- 
Regards/Gruss,
    Boris.

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