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Date: Fri, 22 Mar 2019 17:01:51 +0100 (CET) From: Thomas Gleixner <tglx@...utronix.de> To: Zhao Yakui <yakui.zhao@...el.com> cc: linux-kernel@...r.kernel.org, x86@...nel.org, Jason Chen CJ <jason.cj.chen@...el.com> Subject: Re: [RFC PATCH 3/3] arch/x86/acrn: add hypercall for acrn_hypervisor On Thu, 7 Mar 2019, Zhao Yakui wrote: > When acrn_hypervisor is detected, the other module may communicate with Which other module? > the hypervisor to query/config some settings. For example: it can be used > to query the resources in hypervisor and manage the CPU/memory/device/ > interrupt for Guest system. > +++ b/arch/x86/include/asm/acrn_hypercall.h > @@ -0,0 +1,85 @@ > +/* SPDX-License-Identifier: GPL-2.0+ OR BSD-3-Clause */ So the hypercall header is GPL-2.0+ and the acrn.c file is GPL-2.0. Not that I personally care, but is this intended? > +/* > + * acrn_hypercall.h : acrn hypervisor call API > + */ > + > +#ifndef __ACRN_HYPERCALL_H__ > +#define __ACRN_HYPERCALL_H__ > + > +#include <linux/errno.h> > + > +#ifdef CONFIG_ACRN > + > +static inline long acrn_hypercall0(unsigned long hcall_id) > +{ > + > + /* x86-64 System V ABI register usage */ Well, yes. But can you please provide a link to the hypercall specification in the changelog? Also instead of repeating the same comment over and over, explain the calling convention in a top level comment. > + register signed long result asm("rax"); > + register unsigned long r8 asm("r8") = hcall_id; I appreciate the attempt of making this tabular, but it's unreadable and has random white space in it. Also please use 'long' and not 'signed long'. register unsigned long r8 asm("r8") = hcall_id; register long result asm("rax"); > + > + /* Execute vmcall */ > + asm volatile(".byte 0x0F,0x01,0xC1\n" > + : "=r"(result) > + : "r"(r8)); > + > + /* Return result to caller */ Please do not comment the obvious. It's entirely clear that this returns 'result' to the caller. Comments are there to explain what's not obvious. > + return result; > +} Thanks, tglx
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