17:21 <robclark> bbrezill1, robmur01: I don't suppose arm pgtables give us any way to impement VkPhysicalDeviceSparseProperties::residencyNonResidentStrict, ie. setup a mapping not backed by pages, where writes are discarded and reads return zero?

17:50 <robclark> hmm, ok.. looks like qcom has another ACTLR thing to do this

21:26 <robmur01> robclark: not in standard VMSA, no. IIRC Mali GPUs have their own way of doing something like that

21:28 <robclark> yeah, look like for qc there are some implementation defined regs to setup a phys page address that when mapped into pgtables has this behavior

21:28 <robclark> so more arm-smmu-qcom special things, I guess

21:39 <robmur01> yeah, if it's case of setting up a magic PA that you can then then point regular VA mappings at, that sounds like one for the adreno-priv API

21:40 <robmur01> I don't think it's going to generalise, and I don't believe Mali's thing would need to leak into io-pgtable either

21:40 <robmur01> (although I'll leave that to Boris to confirm)

22:44 <robclark> yeah, just a magic PA.. not as bad as I was fearing