The following commit has been merged into the x86/sev branch of tip: Commit-ID: 176db622573f028f85221873ea4577e096785315 Gitweb: https://git.kernel.org/tip/176db622573f028f85221873ea4577e096785315 Author: Michael Roth <michael.roth@xxxxxxx> AuthorDate: Wed, 09 Feb 2022 12:09:59 -06:00 Committer: Borislav Petkov <bp@xxxxxxx> CommitterDate: Wed, 06 Apr 2022 12:59:17 +02:00 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: Borislav Petkov <bp@xxxxxxxxx> Signed-off-by: Michael Roth <michael.roth@xxxxxxx> Signed-off-by: Borislav Petkov <bp@xxxxxxx> Link: https://lore.kernel.org/r/20220307213356.2797205-6-brijesh.singh@xxxxxxx --- arch/x86/boot/msr.h | 26 ++++++++++++++++++++++++++ arch/x86/include/asm/msr.h | 11 +---------- arch/x86/include/asm/shared/msr.h | 15 +++++++++++++++ 3 files changed, 42 insertions(+), 10 deletions(-) create mode 100644 arch/x86/boot/msr.h create mode 100644 arch/x86/include/asm/shared/msr.h diff --git a/arch/x86/boot/msr.h b/arch/x86/boot/msr.h new file mode 100644 index 0000000..aed66f7 --- /dev/null +++ b/arch/x86/boot/msr.h @@ -0,0 +1,26 @@ +/* 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 */ diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h index d42e6c6..65ec196 100644 --- a/arch/x86/include/asm/msr.h +++ b/arch/x86/include/asm/msr.h @@ -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; diff --git a/arch/x86/include/asm/shared/msr.h b/arch/x86/include/asm/shared/msr.h new file mode 100644 index 0000000..1e6ec10 --- /dev/null +++ b/arch/x86/include/asm/shared/msr.h @@ -0,0 +1,15 @@ +/* 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 */