Messages in this thread | | | Date | Thu, 05 Nov 2020 13:12:02 +0000 | From | Marc Zyngier <> | 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. |
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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. -- Jazz is not dead. It just smells funny...
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