Hi, > > > 在 2025/2/13 0:21, Catalin Marinas 写道: > > (catching up with old threads) > > > > On Mon, Dec 09, 2024 at 10:42:54AM +0800, Tong Tiangen wrote: > > > For the arm64 kernel, when it processes hardware memory errors for > > > synchronize notifications(do_sea()), if the errors is consumed within the > > > kernel, the current processing is panic. However, it is not optimal. > > > > > > Take copy_from/to_user for example, If ld* triggers a memory error, even > > > in > > > kernel mode, only the associated process is affected. Killing the user > > > process and isolating the corrupt page is a better choice. > > > > I agree that killing the user process and isolating the page is a better > > choice but I don't see how the latter happens after this patch. Which > > page would be isolated? > > The SEA is triggered when the page with hardware error is read. After > that, the page is isolated in memory_failure() (mf). The processing of > mf is mentioned in the comments of do_sea(). > > /* > * APEI claimed this as a firmware-first notification. > * Some processing deferred to task_work before ret_to_user(). > */ > > Some processing include mf. > > > > > > Add new fixup type EX_TYPE_KACCESS_ERR_ZERO_MEM_ERR to identify insn > > > that can recover from memory errors triggered by access to kernel memory, > > > and this fixup type is used in __arch_copy_to_user(), This make the > > > regular > > > copy_to_user() will handle kernel memory errors. > > > > Is the assumption that the error on accessing kernel memory is > > transient? There's no way to isolate the kernel page and also no point > > in isolating the destination page either. > > Yes, it's transient, the kernel page in mf can't be isolated, the > transient access (ld) of this kernel page is currently expected to kill > the user-mode process to avoid error spread.
I'm not sure about how this works. IIUC, the memory_failure() wouldn't kill any process if page which raises sea is kernel page (because this wasn't mapped). But, to mark the kernel page as posision, I think it also need to call apei_claim_sea() in !user_mode(). What about calling the apei_claim_sea() when fix_exception_me() successed only in !user_mode() case? Thanks. > > The SEA processes synchronization errors. Only hardware errors on the > source page can be detected (Through synchronous ld insn) and processed. > The destination page cannot be processed. > > > >
