On Thu, Mar 01, 2018 at 02:11:34PM -0700, Logan Gunthorpe wrote:
On 01/03/18 02:03 PM, Benjamin Herrenschmidt wrote:
> However, what happens if anything calls page_address() on them ? Some
> DMA ops do that for example, or some devices might ...
Although we could probably work around it with some pain, we rely on
page_address() and virt_to_phys(), etc to work on these pages. So on x86,
yes, it makes it into the linear mapping.
This is pretty easy to do with HMM:
unsigned long hmm_page_to_phys_pfn(struct page *page)
struct hmm_devmem *devmem;
unsigned long ppfn;
/* Sanity test maybe BUG_ON() */
devmem = page->pgmap->data;
ppfn = page_to_page(page) - devmem->pfn_first;
return ppfn + devmem->device_phys_base_pfn;
Note that last field does not exist in today HMM because i did not need
such helper so far but this can be added.