Re: [RFT][PATCH v1 5/6] vfio/ccw: Add kmap_local_page() for memcpy

Christoph Hellwig
2022-06-17T08:44:47Z

On Thu, Jun 16, 2022 at 04:52:11PM -0700, Nicolin Chen wrote:
> The pinned PFN list returned from vfio_pin_pages() is simply converted
> using page_to_pfn() without protection, so direct access via memcpy()
> will crash on S390 if the PFN is an IO PFN. Instead, the pages should
> be touched using kmap_local_page().

I don't see how this helps. kmap_local_page only works for either
pages in the kernel direct map or highmem, but not for memory that needs
to be ioremapped. And there is no highmem on s390.