linux-kernel - Re: [RFC PATCH] genirq: introduce handle_fasteoi_edge

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Message-ID: <847e4b85-f081-e214-dc24-75a7b3c2c885@huawei.com>
Date:   Sat, 15 Apr 2023 09:38:28 +0800
From:   Yipeng Zou <zouyipeng@...wei.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     <tglx@...utronix.de>, <samuel@...lland.org>,
        <oleksandr_tyshchenko@...m.com>, <andy.shevchenko@...il.com>,
        <apatel@...tanamicro.com>, <lvjianmin@...ngson.cn>,
        <linux-kernel@...r.kernel.org>, <chris.zjh@...wei.com>,
        <liaochang1@...wei.com>, James Gowans <jgowans@...zon.com>
Subject: Re: [RFC PATCH] genirq: introduce handle_fasteoi_edge_irq flow
 handler


在 2023/4/14 19:25, Marc Zyngier 写道:
> On Fri, 10 Mar 2023 10:14:17 +0000,
> Yipeng Zou <zouyipeng@...wei.com> wrote:
>> Recently, We have a LPI migration issue on the ARM SMP platform.
>>
>> For example, NIC device generates MSI and sends LPI to CPU0 via ITS,
>> meanwhile irqbalance running on CPU1 set irq affinity of NIC to CPU1,
>> the next interrupt will be sent to CPU2, due to the state of irq is
>> still in progress, kernel does not end up performing irq handler on
>> CPU2, which results in some userland service timeouts, the sequence
>> of events is shown as follows:
>>
>> NIC                     CPU0                    CPU1
>>
>> Generate IRQ#1          READ_IAR
>>                          Lock irq_desc
>>                          Set IRQD_IN_PROGRESS
>>                          Unlock irq_desc
>>                                                  Lock irq_desc
>>                                                  Change LPI Affinity
>>                                                  Unlock irq_desc
>>                          Call irq_handler
>> Generate IRQ#2
>>                                                  READ_IAR
>>                                                  Lock irq_desc
>>                                                  Check IRQD_IN_PROGRESS
>>                                                  Unlock irq_desc
>>                                                  Return from interrupt#2
>>                          Lock irq_desc
>>                          Clear IRQD_IN_PROGRESS
>>                          Unlock irq_desc
>>                          return from interrupt#1
>>
>> For this scenario, The IRQ#2 will be lost. This does cause some exceptions.
> Please see my reply to James at [1]. I'd appreciate if you could give
> that patch a go, which I expect to be a better avenue to fix what is
> effectively a GIC architecture defect.
>
> Thanks,
>
> 	M.
>
> [1] https://lore.kernel.org/all/86pm89kyyt.wl-maz@kernel.org/

Hi Marc:

     Thanks for your time about this issue.

     I have seen your latest patch, and I am preparing the environment 
for testing, I will sent the testing status of this patch later.

-- 
Regards,
Yipeng Zou