Re: [PATCH v8 00/26] APEI in_nmi() rework and SDEI wire-up

[James Morse <james.morse@arm.com>]

Hi Rafael,

On 08/02/2019 11:40, Rafael J. Wysocki wrote:
> On Tuesday, January 29, 2019 7:48:36 PM CET James Morse wrote:
>> This series aims to wire-up arm64's fancy new software-NMI notifications
>> for firmware-first RAS. These need to use the estatus-queue, which is
>> also needed for notifications via emulated-SError. All of these
>> things take the 'in_nmi()' path through ghes_copy_tofrom_phys(), and
>> so will deadlock if they can interact, which they might.

>> Known issues:
>>  * ghes_copy_tofrom_phys() already takes a lock in NMI context, this
>>    series moves that around, and makes sure we never try to take the
>>    same lock from different NMIlike notifications. Since the switch to
>>    queued spinlocks it looks like the kernel can only be 4 context's
>>    deep in spinlock, which arm64 could exceed as it doesn't have a
>>    single architected NMI. This would be fixed by dropping back to
>>    test-and-set when the nesting gets too deep:
>>  lore.kernel.org/r/1548215351-18896-1-git-send-email-longman@redhat.com
>>
>> * Taking an NMI from a KVM guest on arm64 with VHE leaves HCR_EL2.TGE
>>   clear, meaning AT and TLBI point at the guest, and PAN/UAO are squiffy.
>>   Only TLBI matters for APEI, and this is fixed by Julien's patch:
>>  http://lore.kernel.org/r/1548084825-8803-2-git-send-email-julien.thierry@arm.com
>>
>> * Linux ignores the physical address mask, meaning it doesn't call
>>   memory_failure() on all the affected pages if firmware or hypervisor
>>   believe in a different page size. Easy to hit on arm64, (easy to fix too,
>>   it just conflicts with this series)


>> James Morse (26):
>>   ACPI / APEI: Don't wait to serialise with oops messages when
>>     panic()ing
>>   ACPI / APEI: Remove silent flag from ghes_read_estatus()
>>   ACPI / APEI: Switch estatus pool to use vmalloc memory
>>   ACPI / APEI: Make hest.c manage the estatus memory pool
>>   ACPI / APEI: Make estatus pool allocation a static size
>>   ACPI / APEI: Don't store CPER records physical address in struct ghes
>>   ACPI / APEI: Remove spurious GHES_TO_CLEAR check
>>   ACPI / APEI: Don't update struct ghes' flags in read/clear estatus
>>   ACPI / APEI: Generalise the estatus queue's notify code
>>   ACPI / APEI: Don't allow ghes_ack_error() to mask earlier errors
>>   ACPI / APEI: Move NOTIFY_SEA between the estatus-queue and NOTIFY_NMI
>>   ACPI / APEI: Switch NOTIFY_SEA to use the estatus queue
>>   KVM: arm/arm64: Add kvm_ras.h to collect kvm specific RAS plumbing
>>   arm64: KVM/mm: Move SEA handling behind a single 'claim' interface
>>   ACPI / APEI: Move locking to the notification helper
>>   ACPI / APEI: Let the notification helper specify the fixmap slot
>>   ACPI / APEI: Pass ghes and estatus separately to avoid a later copy
>>   ACPI / APEI: Make GHES estatus header validation more user friendly
>>   ACPI / APEI: Split ghes_read_estatus() to allow a peek at the CPER
>>     length
>>   ACPI / APEI: Only use queued estatus entry during
>>     in_nmi_queue_one_entry()
>>   ACPI / APEI: Use separate fixmap pages for arm64 NMI-like
>>     notifications
>>   mm/memory-failure: Add memory_failure_queue_kick()
>>   ACPI / APEI: Kick the memory_failure() queue for synchronous errors
>>   arm64: acpi: Make apei_claim_sea() synchronise with APEI's irq work
>>   firmware: arm_sdei: Add ACPI GHES registration helper
>>   ACPI / APEI: Add support for the SDEI GHES Notification type


> I can apply patches in this series up to and including patch [21/26].
> 
> Do you want me to do that?

9-12, 17-19, 21 are missing any review/ack tags, so I wouldn't ask, but as
you're offering, yes please!


> Patch [22/26] requires an ACK from mm people.
> 
> Patch [23/26] has a problem that randconfig can generate a configuration
> in which memory_failure_queue_kick() is not present, so it is necessary
> to add a CONFIG_MEMORY_FAILURE dependency somewhere for things to
> work (or define an empty stub for that function in case the symbol is
> not set).

Damn-it! Thanks, I was just trying to work that report out...


> If patches [24-26/26] don't depend on the previous two, I can try to
> apply them either, so please let me know.

22-24 depend on each other. Merging 24 without the other two is no-improvement,
so I'd like them to be kept together.

25-26 don't depend on 22-24, but came later so that they weren't affected by the
same race.
(note to self: describe that in the cover letter next time.)


If I apply the tag's and Boris' changes and post a tested v9 as 1-21, 25-26, is
that easier, or does it cause extra work?


Thanks,

James

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