On 30/05/17 11:28, Joerg Roedel wrote:
> On Wed, May 24, 2017 at 07:01:42PM +0100, Jean-Philippe Brucker wrote:
>> * TLB invalidation by range is batched and committed with a single sync.
>>   Batching ATC invalidation is inconvenient, endpoints limit the number of
>>   inflight invalidations. We'd have to count the number of invalidations
>>   queued and send a sync periodically. In addition, I suspect we always
>>   need a sync between TLB and ATC invalidation for the same page.
> This sounds like the number of outstanding ATS invalidations is not
> managed by the SMMU hardware, is that right?

Yes, the hardware doesn't know about ATS queue depth, it simply forwards
invalidations to the root complex. Doing a sync on the SMMU command queue
waits for all completions of outstanding ATS invalidations, but it is up
to the driver to limit ATS invalidations according to queue depth.


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