lkml.org 
[lkml]   [2019]   [Sep]   [3]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    SubjectRe: [PATCH v2 3/4] drm/ttm, drm/vmwgfx: Correctly support support AMD memory encryption
    From
    Date
    This whole thing looks like a fascinating collection of hacks. :)

    ttm is taking a stack-alllocated "VMA" and handing it to vmf_insert_*()
    which obviously are expecting "real" VMAs that are linked into the mm.
    It's extracting some pgprot_t information from the real VMA, making a
    psuedo-temporary VMA, then passing the temporary one back into the
    insertion functions:

    > static vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)
    > {
    ...
    > struct vm_area_struct cvma;
    ...
    > if (vma->vm_flags & VM_MIXEDMAP)
    > ret = vmf_insert_mixed(&cvma, address,
    > __pfn_to_pfn_t(pfn, PFN_DEV));
    > else
    > ret = vmf_insert_pfn(&cvma, address, pfn);

    I can totally see why this needs new exports. But, man, it doesn't seem
    like something we want to keep *feeding*.

    The real problem here is that the encryption bits from the device VMA's
    "true" vma->vm_page_prot don't match the ones that actually get
    inserted, probably because the device ptes need the encryption bits
    cleared but the system memory PTEs need them set *and* they're mixed
    under one VMA.

    The thing we need to stop is having mixed encryption rules under one VMA.

    \
     
     \ /
      Last update: 2019-09-03 21:39    [W:2.571 / U:0.356 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site