Gentle ping. On 2023/2/27 PM1:03, Shuai Xue wrote: > 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. > > [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 | 134 ++++++++++++++++++++++++--------------- > include/acpi/ghes.h | 3 - > mm/memory-failure.c | 13 ---- > 3 files changed, 82 insertions(+), 68 deletions(-) >
