lkml.org 
[lkml]   [2019]   [Apr]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH v2 3/3] arch/x86/acrn: add hypercall for acrn_guest
On Tue, 26 Mar 2019, Zhao Yakui wrote:

> When acrn_hypervisor is detected, the hypercall is needed so that the
> acrn guest can 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.
>
> So the hypercall is added so that the kernel can communicate with the
> low-level acrn-hypervisor. On x86 it is implemented by using vmacll when

is implemented with the VMCALL instruction

> the acrn hypervisor is enabled.
>
> +++ b/arch/x86/include/asm/acrn_hypercall.h
> @@ -0,0 +1,84 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * acrn_hypercall.h : acrn hypervisor call API

No file names in headers please. They are pointless and get out of sync
when files are renamed.

> + */
> +
> +#ifndef __ACRN_HYPERCALL_H__
> +#define __ACRN_HYPERCALL_H__

asm headers start with

__ASM_X86_....

> +
> +#include <linux/errno.h>
> +
> +#ifdef CONFIG_ACRN_GUEST
> +
> +/*
> + * Hypercalls for ACRN Guest
> + *
> + * Hypercall number is passed in r8 register.
> + * Return value will be placed in rax.
> + * Up to 2 arguments are passed in rdi, rsi.
> + */
> +
> +static inline long acrn_hypercall0(unsigned long hcall_id)
> +{
> +

Remove the empty new line please.

> + register long result asm("rax");
> + register unsigned long r8 asm("r8") = hcall_id;

Please order them the other way around, like a reverse christmas tree:

register unsigned long r8 asm("r8") = hcall_id;
register long result asm("rax");

That's way simpler to read.

> + asm volatile(".byte 0x0F,0x01,0xC1\n"
> + : "=r"(result)
> + : "r"(r8));

Please mention in the changelog why this is implemented with bytes and not
with the proper mnemonic. I assume it depends on binutils, so please
document which version of binutils supports the mnemonic.

And in the first function, i.e. hypercall0, add a comment above the asm
volatile() to that effect as well.

Thanks,

tglx

\
 
 \ /
  Last update: 2019-04-05 21:20    [W:0.094 / U:16.676 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site