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| author | Borislav Petkov <borislav.petkov@amd.com> | 2011-12-05 14:28:37 +0100 |
|---|---|---|
| committer | Borislav Petkov <borislav.petkov@amd.com> | 2011-12-05 14:28:37 +0100 |
| commit | ce37defc0f6673f5ca2c92ed5cfcaf290ae7dd16 (patch) | |
| tree | e662613f6ef4629ec8504502a87079c9b93117da /arch/x86/include/asm/msr.h | |
| parent | bd399063976c6c7a09beb4730ed1d93cadbcc739 (diff) | |
| download | linux-0-day-ce37defc0f6673f5ca2c92ed5cfcaf290ae7dd16.tar.gz linux-0-day-ce37defc0f6673f5ca2c92ed5cfcaf290ae7dd16.tar.xz | |
x86: Document rdmsr_safe restrictions
Recently, I got bitten by using rdmsr_safe too early in the boot
process. Document its shortcomings for future reference.
Link: http://lkml.kernel.org/r/4ED5B70F.606@lwfinger.net
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Diffstat (limited to 'arch/x86/include/asm/msr.h')
| -rw-r--r-- | arch/x86/include/asm/msr.h | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/include/asm/msr.h b/arch/x86/include/asm/msr.h index 084ef95274cd7..95203d40ffdde 100644 --- a/arch/x86/include/asm/msr.h +++ b/arch/x86/include/asm/msr.h @@ -169,7 +169,14 @@ static inline int wrmsr_safe(unsigned msr, unsigned low, unsigned high) return native_write_msr_safe(msr, low, high); } -/* rdmsr with exception handling */ +/* + * rdmsr with exception handling. + * + * Please note that the exception handling works only after we've + * switched to the "smart" #GP handler in trap_init() which knows about + * exception tables - using this macro earlier than that causes machine + * hangs on boxes which do not implement the @msr in the first argument. + */ #define rdmsr_safe(msr, p1, p2) \ ({ \ int __err; \ |