On 2023/3/21 PM3:17, mawupeng wrote: > Test-by: Ma Wupeng <mawupeng1@xxxxxxxxxx> > > I have test this on arm64 with following steps: > 1. make memory failure return EBUSY > 2. force a UCE with einj > > Without this patchset, user task will not be kill since memory_failure can > not handle this UCE properly and user task is in D state. The stack can > be found in the end. > With this patchset, user task can be killed even memory_failure return > -EBUSY without doing anything. > > Here is the stack of user task with D state: > > # cat /proc/7001/stack > [<0>] __flush_work.isra.0+0x80/0xa8 > [<0>] __cancel_work_timer+0x144/0x1c8 > [<0>] cancel_work_sync+0x1c/0x30 > [<0>] memory_failure_queue_kick+0x3c/0x88 > [<0>] ghes_kick_task_work+0x28/0x78 > [<0>] task_work_run+0xb8/0x188 > [<0>] do_notify_resume+0x1e0/0x280 > [<0>] el0_da+0x130/0x138 > [<0>] el0t_64_sync_handler+0x68/0xc0 > [<0>] el0t_64_sync+0x188/0x190 Thank you :) Cheers, Shuai > > On 2023/3/17 15:24, Shuai Xue 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. [2][3] 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[1] 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. >> >> [1] https://developer.arm.com/documentation/den0054/latest/ >> [2] https://lore.kernel.org/linux-arm-kernel/20221205160043.57465-4-xiexiuqi@xxxxxxxxxx/T/ >> [3] 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(-) >>
