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

Christoph Hellwig
2025-10-20T12:28:05Z

On Fri, Oct 17, 2025 at 08:55:24AM -0300, Jason Gunthorpe wrote:
> 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:
> > > 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.

Real PCIe device, yes. But we have a lot of stuff mascquerading as
such with is just emulated or special integrated. I.e. a lot of
integrated Intel GPUs claim had issue there.