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

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  [PATCH 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU Suzuki K Poulose <suzuki.poulose@arm.com> - 2016-04-06 13:30 +0200
    Re: [PATCH 4/5] arm64: Verify CPU errata work arounds on hotplugged  CPU Will Deacon <will.deacon@arm.com> - 2016-04-14 19:40 +0200
      Re: [PATCH 4/5] arm64: Verify CPU errata work arounds on hotplugged  CPU Suzuki K Poulose <Suzuki.Poulose@arm.com> - 2016-04-14 19:50 +0200
        Re: [PATCH 4/5] arm64: Verify CPU errata work arounds on hotplugged  CPU Suzuki K Poulose <Suzuki.Poulose@arm.com> - 2016-04-15 16:20 +0200
          Re: [PATCH 4/5] arm64: Verify CPU errata work arounds on hotplugged  CPU Will Deacon <will.deacon@arm.com> - 2016-04-15 16:20 +0200

#1372409 — [PATCH 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 |    2 +-
 arch/arm64/kernel/cpu_errata.c      |   22 ++++++++++++++++++++++
 arch/arm64/kernel/cpufeature.c      |    1 +
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/include/asm/cpufeature.h b/arch/arm64/include/asm/cpufeature.h
index 733b016..d5b7386 100644
--- a/arch/arm64/include/asm/cpufeature.h
+++ b/arch/arm64/include/asm/cpufeature.h
@@ -191,7 +191,7 @@ void __init setup_cpu_features(void);
 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 2fd5780..d35b398 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -101,6 +101,28 @@ 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_CPU)) {
+			int cpu = smp_processor_id();
+
+			if (caps->desc)
+				pr_crit("CPU%d: Detected - %s\n", cpu, caps->desc);
+			pr_crit("CPU%d: Requires an errata work around not detected"
+					" at boot time\n", cpu);
+			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 3ace45f..2f6ce1d 100644
--- a/arch/arm64/kernel/cpufeature.c
+++ b/arch/arm64/kernel/cpufeature.c
@@ -983,6 +983,7 @@ 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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#1379146 — Re: [PATCH 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU

On Wed, Apr 06, 2016 at 12:24:13PM +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.

Hmm, wouldn't it be better not to free the alternative text for errata
workarounds instead?

Will

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#1379168 — Re: [PATCH 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU

On 14/04/16 18:39, Will Deacon wrote:
> On Wed, Apr 06, 2016 at 12:24:13PM +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.
>
> Hmm, wouldn't it be better not to free the alternative text for errata
> workarounds instead?

We could. I don't have a strong opinion. If there are no objections, I could
adopt it.

Cheers
Suzuki

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#1379848 — Re: [PATCH 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU

On 14/04/16 18:49, Suzuki K Poulose wrote:
> On 14/04/16 18:39, Will Deacon wrote:
>> On Wed, Apr 06, 2016 at 12:24:13PM +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.
>>
>> Hmm, wouldn't it be better not to free the alternative text for errata
>> workarounds instead?
>
> We could. I don't have a strong opinion. If there are no objections, I could
> adopt it.

The alternatives have been merged to .init by :

commit 9aa4ec1571da6236 ("arm64: mm: fold alternatives into .init")

Mark,

Do you have any concerns on applying alternatives for CPUs turned online later ?
We have to revert the patch above to get going

Suzuki

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#1379852 — Re: [PATCH 4/5] arm64: Verify CPU errata work arounds on hotplugged CPU

On Fri, Apr 15, 2016 at 03:10:27PM +0100, Suzuki K Poulose wrote:
> On 14/04/16 18:49, Suzuki K Poulose wrote:
> >On 14/04/16 18:39, Will Deacon wrote:
> >>On Wed, Apr 06, 2016 at 12:24:13PM +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.
> >>
> >>Hmm, wouldn't it be better not to free the alternative text for errata
> >>workarounds instead?
> >
> >We could. I don't have a strong opinion. If there are no objections, I could
> >adopt it.
> 
> The alternatives have been merged to .init by :
> 
> commit 9aa4ec1571da6236 ("arm64: mm: fold alternatives into .init")
> 
> Mark,
> 
> Do you have any concerns on applying alternatives for CPUs turned online later ?
> We have to revert the patch above to get going

Well, note that I'm only suggesting that we keep the alternatives for
CPU errata workarounds.

Will

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