Jason Gunthorpe <[email protected]> writes: > On Fri, Aug 07, 2026 at 02:18:31PM +0100, Will Deacon wrote: > >> > I was under the impression that there is a possibility of using swiotlb >> > instead of restricted-dma-pool with pKVM. >> >> Yes, that patch enables swiotlb as a possibility for protected guests >> but with your patch we avoid shrinking the swiotlb buffer even when >> restricted dma pools are being used and that's a waste of memory. > > I also thought we switched pkvm to use CC-like swiotlb as part of the > alignment in this rework? Mostafa ? > >> > If that is not the case, then we could change: >> > >> > !cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT) && >> > >> > to >> > >> > !is_realm_world() && >> >> Perhaps, or you could just pass the swiotlb= option if the defaults don't >> work for you. Can you give more details about the slots exhaustion you're >> seeing under CCA? > > We see badness with swiotlb too, it basically doesn't work out of the > box if you have to use it 100% for real devices. It easily runs out > of memory. > > Auto tuning to higher levels makes sense to me, but I'd rather the > core code handled adjusting its size to the estimated need, not arch > code.
Agreed -aneesh
