diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2019-07-17 21:18:59 +0200 |
|---|---|---|
| committer | Ben Hutchings <ben@decadent.org.uk> | 2019-08-13 12:39:22 +0100 |
| commit | 822ef687a0a8e92fab6c12e3c2b5e1a5f1a97d54 (patch) | |
| tree | d8137c5c2d52317bd6ac45aed698d62ee7054897 /arch/x86/include | |
| parent | e191f5119eba311b3585492174825db763eeb3b9 (diff) | |
x86/speculation/swapgs: Exclude ATOMs from speculation through SWAPGS
commit f36cf386e3fec258a341d446915862eded3e13d8 upstream.
Intel provided the following information:
On all current Atom processors, instructions that use a segment register
value (e.g. a load or store) will not speculatively execute before the
last writer of that segment retires. Thus they will not use a
speculatively written segment value.
That means on ATOMs there is no speculation through SWAPGS, so the SWAPGS
entry paths can be excluded from the extra LFENCE if PTI is disabled.
Create a separate bug flag for the through SWAPGS speculation and mark all
out-of-order ATOMs and AMD/HYGON CPUs as not affected. The in-order ATOMs
are excluded from the whole mitigation mess anyway.
Reported-by: Andrew Cooper <andrew.cooper3@citrix.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Tyler Hicks <tyhicks@canonical.com>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
[bwh: Backported to 3.16:
- There's no whitelist entry (or any support) for Hygon CPUs
- Use the next available X86_BUG number
- Adjust context, indentation]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Diffstat (limited to 'arch/x86/include')
| -rw-r--r-- | arch/x86/include/asm/cpufeatures.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h index 4e79d301d208..ba48ab887acf 100644 --- a/arch/x86/include/asm/cpufeatures.h +++ b/arch/x86/include/asm/cpufeatures.h @@ -278,5 +278,6 @@ #define X86_BUG_L1TF X86_BUG(9) /* CPU is affected by L1 Terminal Fault */ #define X86_BUG_MDS X86_BUG(10) /* CPU is affected by Microarchitectural data sampling */ #define X86_BUG_MSBDS_ONLY X86_BUG(11) /* CPU is only affected by the MSDBS variant of BUG_MDS */ +#define X86_BUG_SWAPGS X86_BUG(12) /* CPU is affected by speculation through SWAPGS */ #endif /* _ASM_X86_CPUFEATURES_H */ |