Commit 176db622 authored by Michael Roth's avatar Michael Roth Committed by Borislav Petkov
Browse files

x86/boot: Introduce helpers for MSR reads/writes 



The current set of helpers used throughout the run-time kernel have
dependencies on code/facilities outside of the boot kernel, so there
are a number of call-sites throughout the boot kernel where inline
assembly is used instead. More will be added with subsequent patches
that add support for SEV-SNP, so take the opportunity to provide a basic
set of helpers that can be used by the boot kernel to reduce reliance on
inline assembly.

Use boot_* prefix so that it's clear these are helpers specific to the
boot kernel to avoid any confusion with the various other MSR read/write
helpers.

  [ bp: Disambiguate parameter names and trim comment. ]

Suggested-by: default avatarBorislav Petkov <bp@alien8.de>
Signed-off-by: default avatarMichael Roth <michael.roth@amd.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Link: https://lore.kernel.org/r/20220307213356.2797205-6-brijesh.singh@amd.com
parent 6d3b3d34

arch/x86/boot/msr.h

0 → 100644
+26 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0-only */

/*

 * Helpers/definitions related to MSR access.

 */



#ifndef BOOT_MSR_H

#define BOOT_MSR_H



#include <asm/shared/msr.h>



/*

 * The kernel proper already defines rdmsr()/wrmsr(), but they are not for the

 * boot kernel since they rely on tracepoint/exception handling infrastructure

 * that's not available here.

 */

static inline void boot_rdmsr(unsigned int reg, struct msr *m)

{

	asm volatile("rdmsr" : "=a" (m->l), "=d" (m->h) : "c" (reg));

}



static inline void boot_wrmsr(unsigned int reg, const struct msr *m)

{

	asm volatile("wrmsr" : : "c" (reg), "a"(m->l), "d" (m->h) : "memory");

}



#endif /* BOOT_MSR_H */

arch/x86/include/asm/msr.h

+1 −10
Original line number Diff line number Diff line
@@ -10,16 +10,7 @@ 
#include <asm/errno.h>

#include <asm/cpumask.h>

#include <uapi/asm/msr.h>



struct msr {

	union {

		struct {

			u32 l;

			u32 h;

		};

		u64 q;

	};

};

#include <asm/shared/msr.h>



struct msr_info {

	u32 msr_no;

arch/x86/include/asm/shared/msr.h

0 → 100644
+15 −0
Original line number Diff line number Diff line 
/* SPDX-License-Identifier: GPL-2.0 */

#ifndef _ASM_X86_SHARED_MSR_H

#define _ASM_X86_SHARED_MSR_H



struct msr {

	union {

		struct {

			u32 l;

			u32 h;

		};

		u64 q;

	};

};



#endif /* _ASM_X86_SHARED_MSR_H */