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    SubjectRe: can device drivers return non-ram via vm_ops->nopage?
    On Sat, Mar 20, 2004 at 06:40:22AM -0800, William Lee Irwin III wrote:
    > On Sat, Mar 20, 2004 at 02:30:25PM +0100, Andrea Arcangeli wrote:
    > > Anyways returning to the non-ram returned by ->nopage see the below
    > > email exchange with Jens. the bug triggering of course is the
    > > BUG_ON(!pfn_valid(page_to_pfn(new_page))).
    > > If we want to return non-ram, we could, but I believe we should change
    > > the API to return a pfn not a page_t * if we want to.
    >
    > This would be very helpful for other reasons also. There's a general
    > API issue with drivers that want or need to do this. The one I've

    I'm afraid I'll have to teach ->nopage how to deal with non-ram with
    this page_t API too (changing it to pfn sounds too intrusive in the
    short term), it seems to me that alsa can return non-ram (in the nopage
    callback there's a virt_to_page on some iomm region), and changing alsa
    to use remap_file_pages sounds too intrusive too.

    So in short I believe alsa can corrupt memory randomly starting with
    2.6.5-rc1, and it could only generate machine check crashes in previous
    kernels.

    So for the short term (i.e. next few weeks) we'll have to deal with
    page_t still there...
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