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SubjectRe: [BUG] kernel side can NOT trigger memory error with einj
Shuai Xue <> writes:

> 在 2022/3/18 AM12:57, Luck, Tony 写道:
>>> - rc = apei_exec_run(&trigger_ctx, ACPI_EINJ_TRIGGER_ERROR);
>>> + ptr = kmap(pfn_to_page(pfn));
>>> + tmp = *(ptr + (param1 & ~ PAGE_MASK));
>> That hack works when the trigger action is just trying to access the injected
>> location. But on Intel platforms the trigger "kicks" the patrol scrubber in the
>> memory controller to access the address. So the error is triggered not by
>> an access from the core, but by internal memory controller access.
>> This results in a different error signature (for an uncorrected error injection
>> it will be a UCNA or SRAO in Intel acronym-speak).
> As far as I know, APEI only defines five injection instructions, ACPI_EINJ_READ_REGISTER,
> ACPI_EINJ_NOOP. ACPI_EINJ_TRIGGER_ERROR action should run one of them, I don't see
> any of them will kick the patrol scrubber. For example, trigger with ACPI_EINJ_READ_REGISTER:
> apei_exec_run(&trigger_ctx, ACPI_EINJ_TRIGGER_ERROR)
> __apei_exec_run // ins=0
> => apei_exec_read_register
> => apei_read
> => acpi_os_read_memory
> => acpi_map_vaddr_lookup /* lookup VA of PA from acpi_ioremap */
> => acpi_os_ioremap
> => acpi_os_read_iomem
> => *(u32 *) value = readl(virt_addr);
> As we can see, the error is triggered by access from the core. However, the physical
> address can NOT be mapped by acpi_os_ioremap.
> If I missed anything, please let me know. Thank you very much.

As the name suggested, ACPI_EINJ_READ/WRITE_REGISTER are used to
read/write device registers via iomem. They aren't used to read/write
normal physical memory. If that's needed, you can try some other method
I guess.

If you write a device register, the device can kick the patrol scrubber
for you. This device behavior needs not to be defined in APEI spec.

Best Regards,
Huang, Ying

> Best Regards,
> Shuai

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