linux-kernel - Re: [PATCH] acpi: Fix hed module initialization order when it is built-in

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Message-ID: <a980db9a-831b-c950-e5bf-80d422a91015@huawei.com>
Date: Sat, 28 Dec 2024 18:23:56 +0800
From: Xiaofei Tan <tanxiaofei@...wei.com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>
CC: "Rafael J. Wysocki" <rafael@...nel.org>, <lenb@...nel.org>,
	<linux-acpi@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<M.Chehab@...wei.com>, <roberto.sassu@...wei.com>, <shiju.jose@...wei.com>,
	<prime.zeng@...ilicon.com>, <linuxarm@...wei.com>,
	<mchehab+huawei@...nel.org>
Subject: Re: [PATCH] acpi: Fix hed module initialization order when it is
 built-in

Hi Jonathan,

在 2024/12/24 3:33, Jonathan Cameron 写道:
> On Mon, 23 Dec 2024 17:31:08 +0800
> Xiaofei Tan <tanxiaofei@...wei.com> wrote:
>
>> Hi Rafael,
>>
>> 在 2024/12/11 1:59, Rafael J. Wysocki 写道:
>>> On Fri, Nov 15, 2024 at 4:56 AM Xiaofei Tan <tanxiaofei@...wei.com> wrote:
>>>> When the module hed is built-in, the init order is determined by
>>>> Makefile order.
>>> Are you sure?
>> yes
> We had a similar fix in CXL recently (which is why I suggested this approach
> internally when tanxiaofei mentioned the problem).
>
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/drivers/cxl?id=6575b268157f37929948a8d1f3bafb3d7c055bc1
>
> The related discussion for the CXL patch was the first time I'd come across solution
> to load order for built in cases.
>
Yes :)

>>>> That order violates expectations. Because the module
>>>> hed init is behind evged. RAS records can't be handled in the
>>>> special time window that evged has initialized while hed not.
>>>> If the number of such RAS records is more than the APEI HEST error
>>>> source number, the HEST resources could be occupied all, and then
>>>> could affect subsequent RAS error reporting.
>>> Well, the problem is real, but does the change really prevent it from
>>> happening or does it just increase the likelihood of success?
>> It can be completely solved if the driver used as built-in way. If build HED as a
>> module, it not solved.
> Can we enforce that condition not happening with appropriate Kconfig?
> It's annoying to restrict build options, but if needed to make it work
> then better than not working!

Agree,  i will change ACPI_HED from tristate to bool if there are no other comments, thanks.

>
> Jonathan
>
>
>>> In the latter case, and generally speaking too, it would be better to
>>> add explicit synchronization between evged and hed.
>>>   
>>>> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
>>>> Signed-off-by: Xiaofei Tan <tanxiaofei@...wei.com>
>>>> ---
>>>>    drivers/acpi/Makefile | 8 +++++++-
>>>>    1 file changed, 7 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
>>>> index 61ca4afe83dc..54f60b7922ad 100644
>>>> --- a/drivers/acpi/Makefile
>>>> +++ b/drivers/acpi/Makefile
>>>> @@ -15,6 +15,13 @@ endif
>>>>
>>>>    obj-$(CONFIG_ACPI)             += tables.o
>>>>
>>>> +#
>>>> +# The hed.o needs to be in front of evged.o to avoid the problem that
>>>> +# RAS errors cannot be handled in the special time window of startup
>>>> +# phase that evged has initialized while hed not.
>>>> +#
>>>> +obj-$(CONFIG_ACPI_HED)         += hed.o
>>>> +
>>>>    #
>>>>    # ACPI Core Subsystem (Interpreter)
>>>>    #
>>>> @@ -95,7 +102,6 @@ obj-$(CONFIG_ACPI_HOTPLUG_IOAPIC) += ioapic.o
>>>>    obj-$(CONFIG_ACPI_BATTERY)     += battery.o
>>>>    obj-$(CONFIG_ACPI_SBS)         += sbshc.o
>>>>    obj-$(CONFIG_ACPI_SBS)         += sbs.o
>>>> -obj-$(CONFIG_ACPI_HED)         += hed.o
>>>>    obj-$(CONFIG_ACPI_EC_DEBUGFS)  += ec_sys.o
>>>>    obj-$(CONFIG_ACPI_BGRT)                += bgrt.o
>>>>    obj-$(CONFIG_ACPI_CPPC_LIB)    += cppc_acpi.o
>>>> --
>>>> 2.33.0
>>>>   
>>> .
> .