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.

[xuqiang (M)]

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?