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    SubjectRe: [PATCH v11 1/3] ACPI: APEI: send SIGBUS to current task if synchronous memory error not recovered
    Shuai Xue wrote:
    >
    >
    > On 2024/2/19 17:25, Borislav Petkov wrote:
    > > On Sun, Feb 04, 2024 at 04:01:42PM +0800, 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 when abnormal synchronous
    > >> errors occur. These errors can include situations such as invalid PA,
    > >> unexpected severity, no memory failure config support, invalid GUID
    > >> section, etc. 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.
    > >>
    > >> Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
    > >> ---
    > >> drivers/acpi/apei/ghes.c | 9 +++++++++
    > >> 1 file changed, 9 insertions(+)
    > >>
    > >> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
    > >> index 7b7c605166e0..0892550732d4 100644
    > >> --- a/drivers/acpi/apei/ghes.c
    > >> +++ b/drivers/acpi/apei/ghes.c
    > >> @@ -806,6 +806,15 @@ 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 current task due to memory error not recovered");
    > >> + force_sig(SIGBUS);
    > >> + }
    > >
    > > Except that there are a bunch of CXL GUIDs being handled there too and
    > > this will sigbus those processes now automatically.
    >
    > Before the CXL GUIDs added, @Tony confirmed that the HEST notifications are always
    > asynchronous on x86 platform, so only Synchronous External Abort (SEA) on ARM is
    > delivered as a synchronous notification.
    >
    > Will the CXL component trigger synchronous events for which we need to terminate the
    > current process by sending sigbus to process?

    None of the CXL component errors should be handled as synchronous
    events. They are either asynchronous protocol errors, or effectively
    equivalent to CPER_SEC_PLATFORM_MEM notifications.

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