The aim of this series is to wire arm64's SDEI into APEI. Nothing much has changed since v2, patch 3 is new and the KVM IS_ENABLED() stuff has been cleaned up. Otherwise things are noted in each patch. This touches a few trees, so I'm not sure how best it should be merged. Patches 11 and 12 are reducing a race that is made worse by patch 4, I'd like them to arrive together, even though patch 11 doesn't depend on anything else in the series. (patches 11&12 could be moved to after 8 if that makes things easier) The earlier boiler-plate: What's SDEI? Its ARM's "Software Delegated Exception Interface" [0]. It's used by firmware to tell the OS about firmware-first RAS events. These Software exceptions can interrupt anything, so I describe them as NMI-like. They aren't the only NMI-like way to notify the OS about firmware-first RAS events, the ACPI spec also defines 'NOTFIY_SEA' and 'NOTIFY_SEI'. (Acronyms: SEA, Synchronous External Abort. The CPU requested some memory, but the owner of that memory said no. These are always synchronous with the instruction that caused them. SEI, System-Error Interrupt, commonly called SError. This is an asynchronous external abort, the memory-owner didn't say no at the right point. Collectively these things are called external-aborts How is firmware involved? It traps these and re-injects them into the kernel once its written the CPER records). APEI's GHES code only expects one source of NMI. If a platform implements more than one of these mechanisms, APEI needs to handle the interaction. 'SEA' and 'SEI' can interact as 'SEI' is asynchronous. SDEI can interact with itself: its exceptions can be 'normal' or 'critical', and firmware could use both types for RAS. (errors using normal, 'panic-now' using critical). What does this series do? Patches 1-4 refactor APEIs 'estatus queue' so it can be used for all NMI-like notifications. This defers the NMI work to irq_work, which will happen when we next unmask interrupts. Patches 5&6 move the arch and KVM code around so that NMI-like notifications are always called in_nmi(). Patch 7 changes the 'irq or nmi?' path through ghes_copy_tofrom_phys() to be per-ghes. When called in_nmi(), the struct ghes is expected to provide a fixmap slot and lock that is safe to use. NMI-like notifications that mask each other can share these resources. Those that interact should have their own fixmap slot and lock. Patch 8 renames NOTIFY_SEA's use of NOTIFY_NMI's infrastructure, as we're about to have multiple NMI-like users that can't share resources. Pathes 9&10 add the SDEI helper, and notify methods for APEI. After this, adding further firmware-first pieces for arm64 is simple (and safe), and all our NMI-like notifications behave the same as x86's NOTIFY_NMI. All of this makes the race between memory_failure_queue() and ret_to_user worse, as there is now always irq_work involved. Patch 11 makes the reschedule to memory_failure() run as soon as possible. Patch 12 makes sure the arch code knows whether the irq_work has run by the time do_sea() returns. We can skip the signalling step if it has as APEI has done its work. ghes.c became clearer to me when I worked out that it has three sets of functions with 'estatus' in the name. One is a pool of memory that can be allocated-from atomically. This is grown/shrunk when new NMI users are allocated. The second is the estatus-cache, which holds recent notifications so it can suppress notifications we've already handled. The last it the estatus-queue, which holds data from NMI-like notifications (in pool memory) to be processed from irq_work. Testing? Tested with the SDEI FVP based software model and a mocked up NOTFIY_SEA using KVM. I've added a case where 'corrected errors' are discovered at probe time to exercise ghes_probe() during boot. I've only build tested this on x86. Thanks, James [0] http://infocenter.arm.com/help/topic/com.arm.doc.den0054a/ARM_DEN0054A_Software_Delegated_Exception_Interface.pdf James Morse (12): ACPI / APEI: Move the estatus queue code up, and under its own ifdef ACPI / APEI: Generalise the estatus queue's add/remove and notify code ACPI / APEI: don't wait to serialise with oops messages when panic()ing 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: Make the nmi_fixmap_idx per-ghes to allow multiple in_nmi() users ACPI / APEI: Split fixmap pages for arm64 NMI-like notifications firmware: arm_sdei: Add ACPI GHES registration helper ACPI / APEI: Add support for the SDEI GHES Notification type mm/memory-failure: increase queued recovery work's priority arm64: acpi: Make apei_claim_sea() synchronise with APEI's irq work arch/arm/include/asm/kvm_ras.h | 14 + arch/arm/include/asm/system_misc.h | 5 - arch/arm64/include/asm/acpi.h | 5 +- arch/arm64/include/asm/daifflags.h | 1 + arch/arm64/include/asm/fixmap.h | 8 +- arch/arm64/include/asm/kvm_ras.h | 24 ++ arch/arm64/include/asm/system_misc.h | 2 - arch/arm64/kernel/acpi.c | 49 ++++ arch/arm64/mm/fault.c | 30 +- drivers/acpi/apei/ghes.c | 517 ++++++++++++++++++++--------------- drivers/firmware/arm_sdei.c | 77 ++++++ include/acpi/ghes.h | 4 + include/linux/arm_sdei.h | 8 + mm/memory-failure.c | 11 +- virt/kvm/arm/mmu.c | 4 +- 15 files changed, 499 insertions(+), 260 deletions(-) create mode 100644 arch/arm/include/asm/kvm_ras.h create mode 100644 arch/arm64/include/asm/kvm_ras.h -- 2.16.2
