arm64: Always enable ssb vulnerability detection

Ensure we are always able to detect whether or not the CPU is affected
by SSB, so that we can later advertise this to userspace.

Signed-off-by: Jeremy Linton <jeremy.linton@arm.com>
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
[will: Use IS_ENABLED instead of #ifdef]
Signed-off-by: Will Deacon <will.deacon@arm.com>

2 files changed, 5 insertions, 8 deletions

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index e505e1fbd2b9..6ccdc97e5d6a 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -638,11 +638,7 @@ static inline int arm64_get_ssbd_state(void)
 #endif
 }
 
-#ifdef CONFIG_ARM64_SSBD
 void arm64_set_ssbd_mitigation(bool state);
-#else
-static inline void arm64_set_ssbd_mitigation(bool state) {}
-#endif
 
 extern int do_emulate_mrs(struct pt_regs *regs, u32 sys_reg, u32 rt);
 
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index d2bbafa04b3c..b6132783e8cf 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -275,7 +275,6 @@ static int detect_harden_bp_fw(void)
         return 1;
 }
 
-#ifdef CONFIG_ARM64_SSBD
 DEFINE_PER_CPU_READ_MOSTLY(u64, arm64_ssbd_callback_required);
 
 int ssbd_state __read_mostly = ARM64_SSBD_KERNEL;
@@ -348,6 +347,11 @@ void __init arm64_enable_wa2_handling(struct alt_instr *alt,
 
 void arm64_set_ssbd_mitigation(bool state)
 {
+        if (!IS_ENABLED(CONFIG_ARM64_SSBD)) {
+                pr_info_once("SSBD disabled by kernel configuration\n");
+                return;
+        }
+
         if (this_cpu_has_cap(ARM64_SSBS)) {
                 if (state)
                         asm volatile(SET_PSTATE_SSBS(0));
@@ -467,7 +471,6 @@ out_printmsg:
 
         return required;
 }
-#endif  /* CONFIG_ARM64_SSBD */
 
 static void __maybe_unused
 cpu_enable_cache_maint_trap(const struct arm64_cpu_capabilities *__unused)
@@ -759,14 +762,12 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
                 ERRATA_MIDR_RANGE_LIST(arm64_harden_el2_vectors),
         },
 #endif
-#ifdef CONFIG_ARM64_SSBD
         {
                 .desc = "Speculative Store Bypass Disable",
                 .capability = ARM64_SSBD,
                 .type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
                 .matches = has_ssbd_mitigation,
         },
-#endif
 #ifdef CONFIG_ARM64_ERRATUM_1188873
         {
                 /* Cortex-A76 r0p0 to r2p0 */