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[PATCH v4 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU

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  [PATCH v4 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-04-22 13:30 +0200
    Re: [PATCH v4 4/5] arm64: Verify CPU errata work arounds on  hotplugged CPU Catalin Marinas <catalin.marinas@arm.com> - 2016-04-22 15:50 +0200
      Re: [PATCH v4 4/5] arm64: Verify CPU errata work arounds on  hotplugged CPU Suzuki K Poulose <Suzuki.Poulose@arm.com> - 2016-04-22 15:50 +0200

#1385038 — [PATCH v4 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.
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.

Cc: Will Deacon <will.deacon@arm.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Andre Przywara <andre.przywara@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.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 79ec6c6..1cc3446 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -993,6 +993,7 @@ 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

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#1385187 — Re: [PATCH v4 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU

On Fri, Apr 22, 2016 at 12:25:34PM +0100, Suzuki K. Poulose wrote:
> CPU Errata work arounds are detected and applied to the
> kernel code at boot time and the data is then freed up.
> 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.
> 
> Cc: Will Deacon <will.deacon@arm.com>
> Cc: Mark Rutland <mark.rutland@arm.com>
> Cc: Andre Przywara <andre.przywara@arm.com>
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>

I think Will commented on this previously. Was a decision made to leave
this patch as it is and subsequently add support for enabling local
workarounds for hot-plugged CPUs? I'm fine with this given that most
per-CPU workarounds like undocumented bits are set by firmware. But I'd
like to see it done properly once we have a workaround that needs
per-CPU enabling.

Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

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#1385189 — Re: [PATCH v4 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU

On 22/04/16 14:40, Catalin Marinas wrote:
> On Fri, Apr 22, 2016 at 12:25:34PM +0100, Suzuki K. Poulose wrote:
>> CPU Errata work arounds are detected and applied to the
>> kernel code at boot time and the data is then freed up.
>> 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.
>>
>> Cc: Will Deacon <will.deacon@arm.com>
>> Cc: Mark Rutland <mark.rutland@arm.com>
>> Cc: Andre Przywara <andre.przywara@arm.com>
>> Cc: Catalin Marinas <catalin.marinas@arm.com>
>> Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
>
> I think Will commented on this previously. Was a decision made to leave
> this patch as it is and subsequently add support for enabling local
> workarounds for hot-plugged CPUs? I'm fine with this given that most

Yes. Applying work arounds for a hot-plugged CPU will be addressed in a
new series. I updated the cover letter, but missed to update the same here.

>
> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com>

Thanks
Suzuki

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