linux-kernel - Re: [PATCH -next] irq-chip/gic-v3-its: Fixed an issue where the ITS executes the residual commands in the queue again when the ITS wakes up from sleep mode.

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Date:   Thu, 5 Nov 2020 22:06:34 +0800
From:   "xuqiang (M)" <xuqiang36@...wei.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     <tglx@...utronix.de>, <linux-kernel@...r.kernel.org>,
        <rui.xiang@...wei.com>
Subject: Re: [PATCH -next] irq-chip/gic-v3-its: Fixed an issue where the ITS
 executes the residual commands in the queue again when the ITS wakes up from
 sleep mode.


在 2020/11/5 21:12, Marc Zyngier 写道:
> Please don't top-post.
>
> On 2020-11-05 11:54, xuqiang (M) wrote:
>> The kernel sends three commands in the following sequence:
>>
>> 1.mapd(deviceA, ITT_addr1, valid:1)
>>
>> 2.mapti(deviceA):ITS write ITT_addr1 memory;
>>
>> 3.mapd(deviceA, ITT_addr1, valid:0) and kfree(ITT_addr1);
>>
>> 4.mapd(deviceA, ITT_addr2, valid:1);
>>
>> 5.mapti(deviceA):ITS write ITT_addr2 memory;
>>
>> In this case, the processor enters the sleep mode. After the kernel
>> performs the suspend operation, the firmware performs the store
>> operation and saves GITS_CBASER and GITS_CWRITER registers.
>>
>> Then, the processor is woken up, and the firmware restores GITS_CBASER
>> and GITS_CWRITER registers. Because GITS_CWRITER register is not 0,
>> ITS will read the above command sequence execution from the command
>> queue, causing ITT_addr1 memory to be trampled.
>
> This cannot work. By doing a memset on the command queue, you are
> only feeding crap to the ITS (command 0 simply does not exist).
> Consider yourself lucky that it doesn't just lock-up.
>
> What needs to happen is the restore sequence that is already in the
> driver, so that the command queue is in a sane state before re-enabling
> the ITS.
>
>         M.


On my platform, ITS_FLAGS_SAVE_SUSPEND_STATE is not set, thus

the first if condition in its_save_disable under list_for_each_entry goes

to the continue, however, I want to set the GITS_CWRITER to 0 at the

end of list_for_each_entry.

Do you have any suggestions about how to do this?