Re: [PATCH 02/10] PCI/P2PDMA: Introduce p2pdma_provider structure for cleaner abstraction
From: Christoph Hellwig <hch@lst.de>
Date: 2025-07-29 10:41:07
Also in:
kvm, linux-iommu, linux-media, linux-mm, linux-pci, lkml
On Tue, Jul 29, 2025 at 11:53:36AM +0300, Leon Romanovsky wrote:
quoted
Because the struct page is the only thing that: a) dma-mapping works on b) is the only place we can discover the routing information, but also more importantly ensure that the underlying page is still present and the device is not hot unplugged, or in a very theoretical worst case replaced by something else.It is correct in general case, but here we are talking about MMIO memory, which is "connected" to device X and routing information is stable.
MMIO is literally the only thing we support to P2P to/from as that is how PCIe P2P is defined. And not, it's not stable - devices can be unplugged, and BARs can be reenumerated.