On 3/26/25 8:27 PM, Nicolin Chen wrote:
> On Wed, Mar 26, 2025 at 03:16:18PM +0100, Eric Auger wrote:
>>> @@ -1395,6 +1403,13 @@ static int smmuv3_cmdq_consume(SMMUv3State *s)
>>>
>>> trace_smmuv3_cmdq_cfgi_cd(sid);
>>> smmuv3_flush_config(sdev);
>>> +
>>> + if (smmuv3_accel_batch_cmds(sdev->smmu, sdev, &batch, &cmd,
>>> + &q->cons, true)) {
>>> + cmd_error = SMMU_CERROR_ILL;
>> I understand you collect all batchable commands all together (those
>> sharing the same dev_cache prop) and the batch is executed either when
>> the cache target changes or at the very end of the queue consumption.
>> Since you don't batch all kinds of commands don't you have a risk to
>> send commands out of order?
> Yes, that could happen. But would it have some real risk?
OK. I don't know but this needs to be studied.
Eric
>
> This practice has an assumption that the guest OS would group
> each batch with a proper CMD_SYNC like Linux does. So it could
> reduce the amount of ioctls. If we can think of some real risk
> when the guest OS doesn't, yes, I think we would have to flush
> the batch if any non-accel command appear in-between.
>
> Thanks
> Nicolin
>
