linux-kernel - Re: [BUG] kernel side can NOT trigger memory error with einj

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Date:   Mon, 21 Mar 2022 10:43:16 +0800
From:   "Huang, Ying" <ying.huang@...el.com>
To:     Shuai Xue <xueshuai@...ux.alibaba.com>
Cc:     "Luck, Tony" <tony.luck@...el.com>,
        "rjw@...ysocki.net" <rjw@...ysocki.net>,
        "lenb@...nel.org" <lenb@...nel.org>,
        "james.morse@....com" <james.morse@....com>,
        "bp@...en8.de" <bp@...en8.de>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "graeme.gregory@...aro.org" <graeme.gregory@...aro.org>,
        "will.deacon@....com" <will.deacon@....com>,
        "myron.stowe@...hat.com" <myron.stowe@...hat.com>,
        "Brown, Len" <len.brown@...el.com>
Subject: Re: [BUG] kernel side can NOT trigger memory error with einj

Shuai Xue <xueshuai@...ux.alibaba.com> 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_READ_REGISTER_VALUE, ACPI_EINJ_WRITE_REGISTER, ACPI_EINJ_WRITE_REGISTER_VALUE and
> 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