Re: [RFC PATCH 00/28] Removing struct page from P2PDMA

From: Christoph Hellwig
Date: Thu Jun 27 2019 - 05:02:31 EST

On Wed, Jun 26, 2019 at 12:31:08PM -0600, Logan Gunthorpe wrote:
> > we have a hole behind len where we could store flag. Preferably
> > optionally based on a P2P or other magic memory types config
> > option so that 32-bit systems with 32-bit phys_addr_t actually
> > benefit from the smaller and better packing structure.
> That seems sensible. The one thing that's unclear though is how to get
> the PCI Bus address when appropriate. Can we pass that in instead of the
> phys_addr with an appropriate flag? Or will we need to pass the actual
> physical address and then, at the map step, the driver has to some how
> lookup the PCI device to figure out the bus offset?

Yes, I think we'll need a lookup mechanism of some kind.