Re: [PATCH v12 1/3] ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered

["Jarkko Sakkinen" <jarkko@kernel.org>]

On Thu Sep 5, 2024 at 6:04 AM EEST, Shuai Xue wrote:
>
>
> 在 2024/9/4 00:09, Jarkko Sakkinen 写道:
> > On Mon Sep 2, 2024 at 6:00 AM EEST, Shuai Xue wrote:
> >> Synchronous error was detected as a result of user-space process accessing
> >> a 2-bit uncorrected error. The CPU will take a synchronous error exception
> >> such as Synchronous External Abort (SEA) on Arm64. The kernel will queue a
> >> memory_failure() work which poisons the related page, unmaps the page, and
> >> then sends a SIGBUS to the process, so that a system wide panic can be
> >> avoided.
> >>
> >> However, no memory_failure() work will be queued unless all bellow
> >> preconditions check passed:
> >>
> >> - `if (!(mem_err->validation_bits & CPER_MEM_VALID_PA))` in ghes_handle_memory_failure()
> >> - `if (flags == -1)` in ghes_handle_memory_failure()
> >> - `if (!IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE))` in ghes_do_memory_failure()
> >> - `if (!pfn_valid(pfn) && !arch_is_platform_page(physical_addr)) ` in ghes_do_memory_failure()
> >>
> >> In such case, the user-space process will trigger SEA again.  This loop
> >> can potentially exceed the platform firmware threshold or even trigger a
> >> kernel hard lockup, leading to a system reboot.
> >>
> >> Fix it by performing a force kill if no memory_failure() work is queued
> >> for synchronous errors.
> >>
> >> Suggested-by: Xiaofei Tan <tanxiaofei@huawei.com>
> >> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
> >>
> >> ---
> >>   drivers/acpi/apei/ghes.c | 10 ++++++++++
> >>   1 file changed, 10 insertions(+)
> >>
> >> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> >> index 623cc0cb4a65..b0b20ee533d9 100644
> >> --- a/drivers/acpi/apei/ghes.c
> >> +++ b/drivers/acpi/apei/ghes.c
> >> @@ -801,6 +801,16 @@ static bool ghes_do_proc(struct ghes *ghes,
> >>   		}
> >>   	}
> >>   
> >> +	/*
> >> +	 * If no memory failure work is queued for abnormal synchronous
> >> +	 * errors, do a force kill.
> >> +	 */
> >> +	if (sync && !queued) {
> >> +		pr_err("Sending SIGBUS to %s:%d due to hardware memory corruption\n",
> >> +			current->comm, task_pid_nr(current));
> > 
> > Hmm... doest this need "hardware" or would "memory corruption" be
> > enough?
> > 
> > Also, does this need to say that it is sending SIGBUS when the signal
> > itself tells that already?
> > 
> > I.e. could "%s:%d has memory corruption" be enough information?
>
> Hi, Jarkko,
>
> Thank you for your suggestion. Maybe it could.
>
> There are some similar error info which use "hardware memory error", e.g.

By tweaking my original suggestion just a bit:

"%s:%d: hardware memory corruption"

Can't get clearer than that, right?

BR, Jarkko