For AMD hardware, the RETPOLINE_AMD feature is dependent on LFENCE being a serializing instruction. Create a function to allow RETPOLINE_AMD to be cleared if it cannot be determined that LFENCE is serializing. In addition, update the spectre_v2_enabled variable so that sysfs output is correct.
Signed-off-by: Tom Lendacky <[email protected]> --- arch/x86/include/asm/nospec-branch.h | 1 + arch/x86/kernel/cpu/bugs.c | 10 ++++++++++ 2 files changed, 11 insertions(+) diff --git a/arch/x86/include/asm/nospec-branch.h b/arch/x86/include/asm/nospec-branch.h index 8ddf851..5785684 100644 --- a/arch/x86/include/asm/nospec-branch.h +++ b/arch/x86/include/asm/nospec-branch.h @@ -153,6 +153,7 @@ #endif void spectre_v2_check_boottime_disable(void); +void retpoline_amd_disable(void); #endif /* __ASSEMBLY__ */ #endif /* __NOSPEC_BRANCH_H__ */ diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index b957f77..a4c594c 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -170,6 +170,16 @@ void __init spectre_v2_check_boottime_disable(void) return; } +void retpoline_amd_disable(void) +{ + if (!boot_cpu_has(X86_FEATURE_RETPOLINE_AMD)) + return; + + setup_clear_cpu_cap(X86_FEATURE_RETPOLINE_AMD); + spectre_v2_enabled = retp_compiler() ? + SPECTRE_V2_RETPOLINE_GENERIC : SPECTRE_V2_RETPOLINE_MINIMAL; +} + #ifdef CONFIG_SYSFS ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
