Re: [PATCH 02/10] PCI/P2PDMA: Introduce p2pdma_provider structure for cleaner abstraction

[Christoph Hellwig]

On Tue, Jul 29, 2025 at 11:53:36AM +0300, Leon Romanovsky wrote:
> > 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.