Jason Gunthorpe <[email protected]> writes: > On Tue, May 19, 2026 at 09:35:30PM +0530, Aneesh Kumar K.V wrote: >> Yes, that also resulted in simpler and cleaner code. >> >> swiotlb_tbl_map_single >> /* >> * If the physical address is encrypted but the device requires >> * decrypted DMA, use a decrypted io_tlb_mem and update the >> * attributes so the caller knows that a decrypted io_tlb_mem >> * was used. >> */ >> if (!(*attrs & DMA_ATTR_CC_SHARED) && force_dma_unencrypted(dev)) >> *attrs |= DMA_ATTR_CC_SHARED; >> >> if (mem->unencrypted != !!(*attrs & DMA_ATTR_CC_SHARED)) >> return (phys_addr_t)DMA_MAPPING_ERROR; > > Yeah, exactly that is so much clearer now that the mem->unecrypted is > tied directly. > > That logic is reversed though, the incoming ATTR_CC doesn't matter for > swiotlb, that is just the source of the memcpy. > > /* swiotlb pool is incorrect for this device */ > if (mem->unencrypted != force_dma_unencrypted(dev)) > return (phys_addr_t)DMA_MAPPING_ERROR; > > /* Force attrs to match the kind of memory in the pool */ > if (mem->unencrypted) > *attrs |= DMA_ATTR_CC_SHARED; > else > *attrs &= ~DMA_ATTR_CC_SHARED; > > > Attrs should be forced to whatever memory swiotlb selected. >
But that will not handle a T=1 device that wants to use swiotlb to bounce unencrypted memory. That is: force_dma_unencrypted(dev) == 0 /* T=1 device */ attrs = DMA_ATTR_CC_SHARED; In that case, it should use an unencrypted io_tlb_mem: mem->unencrypted == 1 -aneesh
