On Thu, Mar 30, 2023 at 8:11 AM Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx> wrote: > > > On 2023/3/21 AM2:03, Rafael J. Wysocki wrote: > > On Fri, Mar 17, 2023 at 8:25 AM Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx> wrote: > >> > >> changes since v2 by addressing comments from Naoya: > >> - rename mce_task_work to sync_task_work > >> - drop ACPI_HEST_NOTIFY_MCE case in is_hest_sync_notify() > >> - add steps to reproduce this problem in cover letter > >> - Link: https://lore.kernel.org/lkml/1aa0ca90-d44c-aa99-1e2d-bd2ae610b088@xxxxxxxxxxxxxxxxx/T/#mb3dede6b7a6d189dc8de3cf9310071e38a192f8e > >> > >> changes since v1: > >> - synchronous events by notify type > >> - Link: https://lore.kernel.org/lkml/20221206153354.92394-3-xueshuai@xxxxxxxxxxxxxxxxx/ > >> > >> Currently, both synchronous and asynchronous error are queued and handled > >> by a dedicated kthread in workqueue. And Memory failure for synchronous > >> error is synced by a cancel_work_sync trick which ensures that the > >> corrupted page is unmapped and poisoned. And after returning to user-space, > >> the task starts at current instruction which triggering a page fault in > >> which kernel will send SIGBUS to current process due to VM_FAULT_HWPOISON. > >> > >> However, the memory failure recovery for hwpoison-aware mechanisms does not > >> work as expected. For example, hwpoison-aware user-space processes like > >> QEMU register their customized SIGBUS handler and enable early kill mode by > >> seting PF_MCE_EARLY at initialization. Then the kernel will directy notify > >> the process by sending a SIGBUS signal in memory failure with wrong > >> si_code: BUS_MCEERR_AO si_code to the actual user-space process instead of > >> BUS_MCEERR_AR. > >> > >> To address this problem: > >> > >> - PATCH 1 sets mf_flags as MF_ACTION_REQUIRED on synchronous events which > >> indicates error happened in current execution context > >> - PATCH 2 separates synchronous error handling into task work so that the > >> current context in memory failure is exactly belongs to the task > >> consuming poison data. > >> > >> Then, kernel will send SIGBUS with proper si_code in kill_proc(). > >> > >> Lv Ying and XiuQi also proposed to address similar problem and we discussed > >> about new solution to add a new flag(acpi_hest_generic_data::flags bit 8) to > >> distinguish synchronous event.  The UEFI community still has no response. > >> After a deep dive into the SDEI TRM, the SDEI notification should be used for > >> asynchronous error. As SDEI TRM describes "the dispatcher can simulate an > >> exception-like entry into the client, **with the client providing an additional > >> asynchronous entry point similar to an interrupt entry point**". The client > >> (kernel) lacks complete synchronous context, e.g. systeam register (ELR, ESR, > >> etc). So notify type is enough to distinguish synchronous event. > >> > >> To reproduce this problem: > >> > >> # STEP1: enable early kill mode > >> #sysctl -w vm.memory_failure_early_kill=1 > >> vm.memory_failure_early_kill = 1 > >> > >> # STEP2: inject an UCE error and consume it to trigger a synchronous error > >> #einj_mem_uc single > >> 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 > >> injecting ... > >> triggering ... > >> signal 7 code 5 addr 0xffffb0d75000 > >> page not present > >> Test passed > >> > >> The si_code (code 5) from einj_mem_uc indicates that it is BUS_MCEERR_AO error > >> and it is not fact. > >> > >> After this patch set: > >> > >> # STEP1: enable early kill mode > >> #sysctl -w vm.memory_failure_early_kill=1 > >> vm.memory_failure_early_kill = 1 > >> > >> # STEP2: inject an UCE error and consume it to trigger a synchronous error > >> #einj_mem_uc single > >> 0: single vaddr = 0xffffb0d75400 paddr = 4092d55b400 > >> injecting ... > >> triggering ... > >> signal 7 code 4 addr 0xffffb0d75000 > >> page not present > >> Test passed > >> > >> The si_code (code 4) from einj_mem_uc indicates that it is BUS_MCEERR_AR error > >> as we expected. > >> > >>  https://developer.arm.com/documentation/den0054/latest/ > >>  https://lore.kernel.org/linux-arm-kernel/20221205160043.57465-4-xiexiuqi@xxxxxxxxxx/T/ > >>  https://lore.kernel.org/lkml/20221209095407.383211-1-lvying6@xxxxxxxxxx/ > >> > >> Shuai Xue (2): > >> ACPI: APEI: set memory failure flags as MF_ACTION_REQUIRED on > >> synchronous events > >> ACPI: APEI: handle synchronous exceptions in task work > >> > >> drivers/acpi/apei/ghes.c | 135 ++++++++++++++++++++++++--------------- > >> include/acpi/ghes.h | 3 - > >> mm/memory-failure.c | 13 ---- > >> 3 files changed, 83 insertions(+), 68 deletions(-) > >> > >> -- > > > > I really need the designated APEI reviewers to give their feedback on this. > > Gentle ping. As already stated in this thread, this series requires reviews from the designated APEI reviewers (Tony, Boris, James). Thanks!