6.1-stable review patch. If anyone has any objections, please let me know.
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From: James Morse james.morse@arm.com
commit e7956c92f396a44eeeb6eaf7a5b5e1ad24db6748 upstream.
is_spectre_bhb_fw_affected() allows the caller to determine if the CPU is known to need a firmware mitigation. CPUs are either on the list of CPUs we know about, or firmware has been queried and reported that the platform is affected - and mitigated by firmware.
This helper is not useful to determine if the platform is mitigated by firmware. A CPU could be on the know list, but the firmware may not be implemented. Its affected but not mitigated.
spectre_bhb_enable_mitigation() handles this distinction by checking the firmware state before enabling the mitigation.
Add a helper to expose this state. This will be used by the BPF JIT to determine if calling firmware for a mitigation is necessary and supported.
Signed-off-by: James Morse james.morse@arm.com Reviewed-by: Catalin Marinas catalin.marinas@arm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/arm64/include/asm/spectre.h | 1 + arch/arm64/kernel/proton-pack.c | 5 +++++ 2 files changed, 6 insertions(+)
--- a/arch/arm64/include/asm/spectre.h +++ b/arch/arm64/include/asm/spectre.h @@ -96,6 +96,7 @@ enum mitigation_state arm64_get_meltdown
enum mitigation_state arm64_get_spectre_bhb_state(void); bool is_spectre_bhb_affected(const struct arm64_cpu_capabilities *entry, int scope); +bool is_spectre_bhb_fw_mitigated(void); void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *__unused); #endif /* __ASSEMBLY__ */ #endif /* __ASM_SPECTRE_H */ --- a/arch/arm64/kernel/proton-pack.c +++ b/arch/arm64/kernel/proton-pack.c @@ -1108,6 +1108,11 @@ void spectre_bhb_enable_mitigation(const update_mitigation_state(&spectre_bhb_state, state); }
+bool is_spectre_bhb_fw_mitigated(void) +{ + return test_bit(BHB_FW, &system_bhb_mitigations); +} + /* Patched to NOP when enabled */ void noinstr spectre_bhb_patch_loop_mitigation_enable(struct alt_instr *alt, __le32 *origptr,