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

[Shuai Xue]

在 2024/9/5 22:17, Jarkko Sakkinen 写道:
> On Thu Sep 5, 2024 at 5:14 PM EEST, Jarkko Sakkinen wrote:
> > 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@xxxxxxxxxx>
> > > > > Signed-off-by: Shuai Xue <xueshuai@xxxxxxxxxxxxxxxxx>
> > > > >
> > > > > ---
> > > > >    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?
>
> And obvious reason that shorter and more consistent klog message is easy
> to spot and grep. It is simply less convoluted.
>
> If you want also SIGBUS, I'd just put it as "%s:%d: hardware memory
> corruption (SIGBUS)"
>
> BR, Jarkko

Hi, Jarkko,

I will change it to "%s:%d: hardware memory corruption (SIGBUS)".

Thank you for valuable suggestion.

Best Regards,
Shuai