Re: [PATCH 2/2] xen: swiotlb: Implement map_resource callback

[Christoph Hellwig <hch@xxxxxxxxxxxxx>]

On Wed, May 07, 2025 at 04:09:15PM -0700, Stefano Stabellini wrote:
> > This mapping is not for a RAM backed address. In the eDMA case for the 
> > iMX8QXP the `phys` coming in here is the address of a register.
> 
> Ok, this information is important :-)
> 
> I am not certain whether the map_resource interface can only be called
> for MMIO addresses or if it can also be called for RAM-backed addresses
> with a size > PAGE_SIZE. In the latter case, we could run into the issue
> I was describing.

map_resource is intended for MMIO regions, although those could be >
PAGE_SIZE.  It must not be called on RAM.