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