linux-kernel - [PATCH 5.9 21/74] arm64: Run ARCH_WORKAROUND

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Message-Id: <20201031113501.062635343@linuxfoundation.org>
Date:   Sat, 31 Oct 2020 12:36:03 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Suzuki K Poulose <suzuki.poulose@....com>,
        Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>
Subject: [PATCH 5.9 21/74] arm64: Run ARCH_WORKAROUND_2 enabling code on all CPUs

From: Marc Zyngier <maz@...nel.org>

commit 39533e12063be7f55e3d6ae21ffe067799d542a4 upstream.

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
mitigated.

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@...r.kernel.org>
Reviewed-by: Suzuki K Poulose <suzuki.poulose@....com>
Signed-off-by: Marc Zyngier <maz@...nel.org>
Signed-off-by: Will Deacon <will@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 arch/arm64/kernel/cpu_errata.c |    7 +++++++
 1 file changed, 7 insertions(+)

--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -457,6 +457,12 @@ out_printmsg:
 	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[] = {
 	MIDR_ALL_VERSIONS(MIDR_CORTEX_A35),
@@ -914,6 +920,7 @@ const struct arm64_cpu_capabilities arm6
 		.capability = ARM64_SSBD,
 		.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
 		.matches = has_ssbd_mitigation,
+		.cpu_enable = cpu_enable_ssbd_mitigation,
 		.midr_range_list = arm64_ssb_cpus,
 	},
 #ifdef CONFIG_ARM64_ERRATUM_1418040