Re: [PATCH v5 8/9] vfio/pci: Enable peer-to-peer DMA transactions by default

On Thu, Oct 16, 2025 at 11:32:59PM -0700, Christoph Hellwig wrote:

On Mon, Oct 13, 2025 at 06:26:10PM +0300, Leon Romanovsky wrote:

quoted

From: Leon Romanovsky <leonro@nvidia.com>

Make sure that all VFIO PCI devices have peer-to-peer capabilities
enables, so we would be able to export their MMIO memory through DMABUF,

How do you know that they are safe to use with P2P?

All PCI devices are "safe" for P2P by spec. I've never heard of a
non-complaint device causing problems in this area.

The issue is always SOC support inside the CPU and that is delt with
inside the P2P subsystem logic.

If we ever see a problem it would be delt with by quirking the broken
device through pci-quirks and having the p2p subsystem refuse any p2p
with that device.

Jason