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| author | Daniel Sneddon <daniel.sneddon@linux.intel.com> | 2023-07-13 04:43:13 +0200 |
|---|---|---|
| committer | Dave Hansen <dave.hansen@linux.intel.com> | 2023-07-21 22:02:35 +0200 |
| commit | 53cf5797f114ba2bd86d23a862302119848eff19 (patch) | |
| tree | 11cf22869eabd05aaeccd71feb7cb0fd9a6719a7 | |
| parent | x86/speculation: Add force option to GDS mitigation (diff) | |
| download | linux-53cf5797f114ba2bd86d23a862302119848eff19.tar.xz linux-53cf5797f114ba2bd86d23a862302119848eff19.zip | |
x86/speculation: Add Kconfig option for GDS
Gather Data Sampling (GDS) is mitigated in microcode. However, on
systems that haven't received the updated microcode, disabling AVX
can act as a mitigation. Add a Kconfig option that uses the microcode
mitigation if available and disables AVX otherwise. Setting this
option has no effect on systems not affected by GDS. This is the
equivalent of setting gather_data_sampling=force.
Signed-off-by: Daniel Sneddon <daniel.sneddon@linux.intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Acked-by: Josh Poimboeuf <jpoimboe@kernel.org>
| -rw-r--r-- | arch/x86/Kconfig | 19 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/bugs.c | 4 |
2 files changed, 23 insertions, 0 deletions
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 7422db409770..36d3f61c4ed9 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -2603,6 +2603,25 @@ config SLS against straight line speculation. The kernel image might be slightly larger. +config GDS_FORCE_MITIGATION + bool "Force GDS Mitigation" + depends on CPU_SUP_INTEL + default n + help + Gather Data Sampling (GDS) is a hardware vulnerability which allows + unprivileged speculative access to data which was previously stored in + vector registers. + + This option is equivalent to setting gather_data_sampling=force on the + command line. The microcode mitigation is used if present, otherwise + AVX is disabled as a mitigation. On affected systems that are missing + the microcode any userspace code that unconditionally uses AVX will + break with this option set. + + Setting this option on systems not vulnerable to GDS has no effect. + + If in doubt, say N. + endif config ARCH_HAS_ADD_PAGES diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index 155e8d1c325e..41821a4551a2 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -659,7 +659,11 @@ enum gds_mitigations { GDS_MITIGATION_HYPERVISOR, }; +#if IS_ENABLED(CONFIG_GDS_FORCE_MITIGATION) +static enum gds_mitigations gds_mitigation __ro_after_init = GDS_MITIGATION_FORCE; +#else static enum gds_mitigations gds_mitigation __ro_after_init = GDS_MITIGATION_FULL; +#endif static const char * const gds_strings[] = { [GDS_MITIGATION_OFF] = "Vulnerable", |