On Tue, May 19, 2026 at 11:06:52AM +0000, Mostafa Saleh wrote: > > > One other interesting case for device-passthrough is non-coherent > > > devices which then require private pools for bouncing. > > > > Why does shared/private matter for bouncing? Why do you need to bounce > > at all? Do cmo's not work in pkvm guests? > > At the moment, in iommu_dma_map_phys(), if a non coherent device > tries to map an unaligned address or size it will be bounced.
Sure, that's fine. > In pKVM, dma-iommu is used for assigned devices which operate on > private memory, so bouncing that through the SWIOTLB would leak > information from the guest as the SWIOTLB is decrypted. Yes, a device that can do private access should not be using a shared SWIOTLB, that should be part of the selection logic inside the SWIOTLB stuff.. Jason
