linux-kernel - [PATCH v5 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU

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Date:	Tue, 26 Apr 2016 15:48:59 +0100
From:	Suzuki K Poulose <suzuki.poulose@....com>
To:	linux-arm-kernel@...ts.infradead.org
Cc:	mark.rutland@....com, marc.zyngier@....com,
	linux-kernel@...r.kernel.org, will.deacon@....com,
	catalin.marinas@....com, Vadim.Lomovtsev@...iumnetworks.com,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Andre Przywara <andre.przywara@....com>
Subject: [PATCH v5 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU

CPU Errata work arounds are detected and applied to the kernel code at
boot time and the data is then freed up. At the moment if a new
hotplugged CPU requires a work around which was not applied at boot
time, there is nothing we can do but simply fail the booting.
This limitation can be lifted in a follow up series, which
will involve more changes to the alternative work around handling
code.

Cc: Will Deacon <will.deacon@....com>
Cc: Mark Rutland <mark.rutland@....com>
Cc: Andre Przywara <andre.przywara@....com>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@....com>
---
 arch/arm64/include/asm/cpufeature.h |    1 +
 arch/arm64/kernel/cpu_errata.c      |   20 ++++++++++++++++++++
 arch/arm64/kernel/cpufeature.c      |    1 +
 3 files changed, 22 insertions(+)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index d39db63..224efe7 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -193,6 +193,7 @@ void update_cpu_capabilities(const struct arm64_cpu_capabilities *caps,
 			    const char *info);
 void check_local_cpu_errata(void);
 
+void verify_local_cpu_errata(void);
 void verify_local_cpu_capabilities(void);
 
 u64 read_system_reg(u32 id);
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 2fdecd7..d427894 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -103,6 +103,26 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 	}
 };
 
+/*
+ * The CPU Errata work arounds are detected and applied at boot time
+ * and the related information is freed soon after. If the new CPU requires
+ * an errata not detected at boot, fail this CPU.
+ */
+void verify_local_cpu_errata(void)
+{
+	const struct arm64_cpu_capabilities *caps = arm64_errata;
+
+	for (; caps->matches; caps++)
+		if (!cpus_have_cap(caps->capability) &&
+			caps->matches(caps, SCOPE_LOCAL_CPU)) {
+			pr_crit("CPU%d: Requires work around for %s, not detected"
+					" at boot time\n",
+				smp_processor_id(),
+				caps->desc ? : "an erratum");
+			cpu_die_early();
+		}
+}
+
 void check_local_cpu_errata(void)
 {
 	update_cpu_capabilities(arm64_errata, "enabling workaround for");
diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
index 2b09dc4..811773d 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -998,6 +998,7 @@ void verify_local_cpu_capabilities(void)
 	if (!sys_caps_initialised)
 		return;
 
+	verify_local_cpu_errata();
 	verify_local_cpu_features(arm64_features);
 	verify_local_elf_hwcaps(arm64_elf_hwcaps);
 	if (system_supports_32bit_el0())
-- 
1.7.9.5