linux-kernel - [PATCH 5.4 05/49] arm64: Run ARCH_WORKAROUND

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Date:   Sat, 31 Oct 2020 12:35:01 +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 5.4 05/49] arm64: Run ARCH_WORKAROUND_1 enabling code on all CPUs

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

commit 18fce56134c987e5b4eceddafdbe4b00c07e2ae1 upstream.

Commit 73f381660959 ("arm64: Advertise mitigation of Spectre-v2, or lack
thereof") changed the way we deal with ARCH_WORKAROUND_1, by moving most
of the enabling code to the .matches() callback.

This has the unfortunate effect that the workaround gets only enabled on
the first affected CPU, and no other.

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

Fixes: 73f381660959 ("arm64: Advertise mitigation of Spectre-v2, or lack thereof")
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 |    8 ++++++++
 1 file changed, 8 insertions(+)

--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -635,6 +635,12 @@ check_branch_predictor(const struct arm6
 	return (need_wa > 0);
 }
 
+static void
+cpu_enable_branch_predictor_hardening(const struct arm64_cpu_capabilities *cap)
+{
+	cap->matches(cap, SCOPE_LOCAL_CPU);
+}
+
 static const __maybe_unused struct midr_range tx2_family_cpus[] = {
 	MIDR_ALL_VERSIONS(MIDR_BRCM_VULCAN),
 	MIDR_ALL_VERSIONS(MIDR_CAVIUM_THUNDERX2),
@@ -894,9 +900,11 @@ const struct arm64_cpu_capabilities arm6
 	},
 #endif
 	{
+		.desc = "Branch predictor hardening",
 		.capability = ARM64_HARDEN_BRANCH_PREDICTOR,
 		.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
 		.matches = check_branch_predictor,
+		.cpu_enable = cpu_enable_branch_predictor_hardening,
 	},
 #ifdef CONFIG_HARDEN_EL2_VECTORS
 	{