Messages in this thread | | | Date | Fri, 5 Apr 2019 21:19:29 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [RFC PATCH v2 3/3] arch/x86/acrn: add hypercall for acrn_guest |
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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
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