[PATCH 03/19] arm64: Run ARCH_WORKAROUND_2 enabling code on all CPUs

Will Deacon will at kernel.org
Fri Sep 18 12:47:13 EDT 2020

From: Marc Zyngier <maz at kernel.org>

Commit 606f8e7b27bf ("arm64: capabilities: Use linear array for
detection and verification") changed the way we deal with per-CPU errata
by only calling the .matches() callback until one CPU is found to be
affected. At this point, .matches() stop being called, and .cpu_enable()
will be called on all CPUs.

This breaks the ARCH_WORKAROUND_2 handling, as only a single CPU will be

In order to address this, forcefully call the .matches() callback from a
.cpu_enable() callback, which brings us back to the original behaviour.

Fixes: 606f8e7b27bf ("arm64: capabilities: Use linear array for detection and verification")
Cc: <stable at vger.kernel.org>
Signed-off-by: Marc Zyngier <maz at kernel.org>
Signed-off-by: Will Deacon <will at kernel.org>
 arch/arm64/kernel/cpu_errata.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 3fe64bf5a58d..abfef5f3b5fd 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -457,6 +457,12 @@ static bool has_ssbd_mitigation(const struct arm64_cpu_capabilities *entry,
 	return required;
+static void cpu_enable_ssbd_mitigation(const struct arm64_cpu_capabilities *cap)
+	if (ssbd_state != ARM64_SSBD_FORCE_DISABLE)
+		cap->matches(cap, SCOPE_LOCAL_CPU);
 /* known invulnerable cores */
 static const struct midr_range arm64_ssb_cpus[] = {
@@ -914,6 +920,7 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 		.capability = ARM64_SSBD,
 		.matches = has_ssbd_mitigation,
+		.cpu_enable = cpu_enable_ssbd_mitigation,
 		.midr_range_list = arm64_ssb_cpus,
 #ifdef CONFIG_ARM64_ERRATUM_1418040

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