linux-kernel - Re: [PATCH] mbigen: don't clear eventid when free

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Message-ID: <e433c506-33ad-28ce-89f8-27d6897387d2@huawei.com>
Date:   Thu, 21 Mar 2019 21:21:40 +0800
From:   Chen Jianguo <chenjianguo3@...wei.com>
To:     Marc Zyngier <marc.zyngier@....com>
CC:     Thomas Gleixner <tglx@...utronix.de>,
        Jason Cooper <jason@...edaemon.net>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Liyou (leeyou, RTOS)" <leeyou.li@...wei.com>,
        "Joey Yan(Bo)" <joey.yanbo@...wei.com>,
        "Xiaowei (C)" <xiaowei774@...wei.com>,
        "zhanghan (Q)" <zhanghan23@...wei.com>,
        Yangyingliang <yangyingliang@...wei.com>,
        yaohongbo <yaohongbo@...wei.com>, Linuxarm <linuxarm@...wei.com>
Subject: Re: [PATCH] mbigen: don't clear eventid when free_irq


Hi Marc
On 2019/3/21 17:11, Marc Zyngier wrote:
> On Sat, 16 Mar 2019 11:15:03 +0000
> chenjianguo <chenjianguo3@...wei.com> wrote:
>
>> From: Jianguo Chen <chenjianguo3@...wei.com>
>>
>> mbigen_write_msg clears eventid bits of a mbigen register
>> when free a interrupt, because msi_domain_deactivate memset
>> struct msg to zero. Then multiple mbigen pins with zero eventid
>> will report the same interrupt number.
>>
>> The eventid clear call trace:
>>                 free_irq
>>                 __free_irq
>>                 irq_shutdown
>>                 irq_domain_deactivate_irq
>>                 __irq_domain_deactivate_irq
>>                 __irq_domain_deactivate_irq
>>                 msi_domain_deactivate
>>                 platform_msi_write_msg
>>                 mbigen_write_msg
>>
>> Signed-off-by: Jianguo Chen <chenjianguo3@...wei.com>
>> ---
>>   drivers/irqchip/irq-mbigen.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/irqchip/irq-mbigen.c b/drivers/irqchip/irq-mbigen.c
>> index 567b29c..fad7291 100644
>> --- a/drivers/irqchip/irq-mbigen.c
>> +++ b/drivers/irqchip/irq-mbigen.c
>> @@ -161,6 +161,9 @@ static void mbigen_write_msg(struct msi_desc *desc,
>> struct msi_msg *msg)
>>         void __iomem *base = d->chip_data;
>>         u32 val;
>>
>> +       if (!msg->address_lo && !msg->address_hi)
>> +               return;
>> +
>>         base += get_mbigen_vec_reg(d->hwirq);
>>         val = readl_relaxed(base);
>>
>
> For whatever reason, I couldn't apply this patch (even when fishing a
> copy of this email from the archives). It seems to be corrupted is
> various ways, so I had to write the patch from scratch, which is not the
> most reliable way to work. Good thing this was something trivial, I
> wouldn't do it for something more complicated.
>
> In the future, please make sure to use 'git send-email' to send your
> patches, as it is known to work correctly.
>
> Thanks,
>
> 	M.
>

  Mbigen vector register and pin structure shows as below:

	event id       0      1     2          127
    vector register    reg0  reg1  reg2       reg127
			|     |     |           |
	  MBIGEN	pin0  pin1  pin2  ...  pin127
         		|-----|-----|-----|-----|
			|     |     |     |     |
       device interrupt num0 num1  num2       num127

Suppose a device driver requested irq num0 and num1 at the beginning, 
and for some reason it freed irq num1, mbigen_write_msg will write reg1 
with event id 0. Then the pin1 probably mistakenly report interrupt num0 
to device driver if there is a signal on the pin.


	event id       0      0     2          127
    vector register    reg0  reg1  reg2       reg127
			|     |     |           |
	  MBIGEN	pin0  pin1  pin2  ...  pin127
         		|-----|-----|-----|-----|
			|     |     |     |     |
	device interrup num0 num1  num2       num127		

Thanks,
	Jianguo Chen