From: Thomas Gleixner <tglx@linutronix.de>
To: Zhao Yakui <yakui.zhao@intel.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
Jason Chen CJ <jason.cj.chen@intel.com>
Subject: Re: [RFC PATCH v2 3/3] arch/x86/acrn: add hypercall for acrn_guest
Date: Fri, 5 Apr 2019 21:19:29 +0200 (CEST) [thread overview]
Message-ID: <alpine.DEB.2.21.1904052110370.1802@nanos.tec.linutronix.de> (raw)
In-Reply-To: <1553576023-6434-4-git-send-email-yakui.zhao@intel.com>
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
next prev parent reply other threads:[~2019-04-05 19:19 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-26 4:53 [RFC PATCH v2 0/3] arch/x86: Add the support of ACRN guest under arch/x86 Zhao Yakui
2019-03-26 4:53 ` [RFC PATCH v2 1/3] arch/x86: add the support of ACRN guest Zhao Yakui
2019-04-05 19:01 ` Thomas Gleixner
2019-04-08 3:36 ` Zhao, Yakui
2019-03-26 4:53 ` [RFC PATCH v2 2/3] arch/x86/acrn: Use HYPERVISOR_CALLBACK_VECTOR for Acrn upcall vector Zhao Yakui
2019-04-05 19:07 ` Thomas Gleixner
2019-04-08 3:33 ` Zhao, Yakui
2019-03-26 4:53 ` [RFC PATCH v2 3/3] arch/x86/acrn: add hypercall for acrn_guest Zhao Yakui
2019-04-05 19:19 ` Thomas Gleixner [this message]
2019-04-08 3:31 ` Zhao, Yakui
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