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| author | Thomas Gleixner <tglx@linutronix.de> | 2022-09-15 14:11:19 +0300 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-10-17 17:41:11 +0300 |
| commit | 80e4c1cd42fff110bfdae8fce7ac4f22465f9664 (patch) | |
| tree | 72eb9d2152e2c6af9f82d92c4508302b0d044fe8 /arch/x86/include/asm/disabled-features.h | |
| parent | bea75b33895f7f87f0c40023e36a2d087e87ffa1 (diff) | |
| download | linux-80e4c1cd42fff110bfdae8fce7ac4f22465f9664.tar.xz | |
x86/retbleed: Add X86_FEATURE_CALL_DEPTH
Intel SKL CPUs fall back to other predictors when the RSB underflows. The
only microcode mitigation is IBRS which is insanely expensive. It comes
with performance drops of up to 30% depending on the workload.
A way less expensive, but nevertheless horrible mitigation is to track the
call depth in software and overeagerly fill the RSB when returns underflow
the software counter.
Provide a configuration symbol and a CPU misfeature bit.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111147.056176424@infradead.org
Diffstat (limited to 'arch/x86/include/asm/disabled-features.h')
| -rw-r--r-- | arch/x86/include/asm/disabled-features.h | 9 |
1 files changed, 8 insertions, 1 deletions
diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h index 33d2cd04d254..bbb03b25263e 100644 --- a/arch/x86/include/asm/disabled-features.h +++ b/arch/x86/include/asm/disabled-features.h @@ -69,6 +69,12 @@ # define DISABLE_UNRET (1 << (X86_FEATURE_UNRET & 31)) #endif +#ifdef CONFIG_CALL_DEPTH_TRACKING +# define DISABLE_CALL_DEPTH_TRACKING 0 +#else +# define DISABLE_CALL_DEPTH_TRACKING (1 << (X86_FEATURE_CALL_DEPTH & 31)) +#endif + #ifdef CONFIG_INTEL_IOMMU_SVM # define DISABLE_ENQCMD 0 #else @@ -101,7 +107,8 @@ #define DISABLED_MASK8 (DISABLE_TDX_GUEST) #define DISABLED_MASK9 (DISABLE_SGX) #define DISABLED_MASK10 0 -#define DISABLED_MASK11 (DISABLE_RETPOLINE|DISABLE_RETHUNK|DISABLE_UNRET) +#define DISABLED_MASK11 (DISABLE_RETPOLINE|DISABLE_RETHUNK|DISABLE_UNRET| \ + DISABLE_CALL_DEPTH_TRACKING) #define DISABLED_MASK12 0 #define DISABLED_MASK13 0 #define DISABLED_MASK14 0 |