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Date: Sun, 28 Apr 2019 09:56:35 +0800 From: "Zhao, Yakui" <yakui.zhao@...el.com> To: Borislav Petkov <bp@...en8.de> 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 2019年04月27日 16:58, Borislav Petkov wrote: > On Fri, Apr 26, 2019 at 11:18:48AM +0800, Zhao, Yakui wrote: >> It seems that it is seldom used in kernel although the explicit register >> variable is supported by GCC and makes the code look simpler. And it seems >> that the explicit register variable is not suppoorted by CLAG. > > The more reason not to do it this way. Also, the "register" variable > specification is not very widespread in x86 when you look at > > $ git grep -E "register\s.*asm" arch/x86/ > > output. Yes. The explicit register variable is not very videspread for arch/x86. So the register variable will be removed for ACRN hypercall. > >> So the explicit register variable will be removed. I will follow the asm >> code from Borislav. Of course one minor change is that the "movq" is used >> instead of "mov". > > Does that matter if your destination register is 64-bit? Thanks for the reminder about the access width. It is 64-bit register. What I said is the "movq", not "movl". (I understand that movl is incorrect for 64-bit register). Thanks Yakui
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