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    SubjectRe: [RFT][PATCH v1 5/6] vfio/ccw: Add kmap_local_page() for memcpy
    On Fri, Jun 17, 2022 at 01:44:30AM -0700, Christoph Hellwig wrote:
    > 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.

    Oh..I will discuss with Jason once he's back, to see if we should
    simply drop this change. Thanks!

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