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arm64: proton-pack: Expose whether the platform is mitigated by firmware

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[ Upstream commit e7956c92f396a44eeeb6eaf7a5b5e1ad24db6748 ]

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>
[The conflicts were due to not include bitmap of mitigations]
Signed-off-by: Pu Lehui <pulehui@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
James Morse
2025-06-07 15:25:12 +00:00
committed by Greg Kroah-Hartman
parent 47072cbab1
commit cde8ad8a7a
2 changed files with 9 additions and 0 deletions
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1
arch/arm64/include/asm/spectre.h
View File

@@ -32,6 +32,7 @@ void spectre_v4_enable_task_mitigation(struct task_struct *tsk);
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);
u8 spectre_bhb_loop_affected(int scope);
void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *__unused);
bool try_emulate_el1_ssbs(struct pt_regs *regs, u32 instr);

8
arch/arm64/kernel/proton-pack.c
View File

@@ -1059,6 +1059,8 @@ static void kvm_setup_bhb_slot(const char *hyp_vecs_start)
static void kvm_setup_bhb_slot(const char *hyp_vecs_start) { }
#endif /* CONFIG_KVM */
static bool spectre_bhb_fw_mitigated;
void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry)
{
enum mitigation_state fw_state, state = SPECTRE_VULNERABLE;
@@ -1103,12 +1105,18 @@ void spectre_bhb_enable_mitigation(const struct arm64_cpu_capabilities *entry)
this_cpu_set_vectors(EL1_VECTOR_BHB_FW);
state = SPECTRE_MITIGATED;
spectre_bhb_fw_mitigated = true;
}
}
update_mitigation_state(&spectre_bhb_state, state);
}
bool is_spectre_bhb_fw_mitigated(void)
{
return spectre_bhb_fw_mitigated;
}
/* Patched to correct the immediate */
void noinstr spectre_bhb_patch_loop_iter(struct alt_instr *alt,
__le32 *origptr, __le32 *updptr, int nr_inst)