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| author | Jason Gunthorpe <jgg@nvidia.com> | 2021-10-20 02:27:31 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2021-11-18 21:17:08 +0300 |
| commit | 71fb40ae9b07578b3aeebf78fcbb3394810acd9a (patch) | |
| tree | 590d3f3b20653b2153410128dc612988e6f62665 /include/drm | |
| parent | 9d5c7b0eeeca313221ccb660b34ea89a56e19aba (diff) | |
| download | linux-71fb40ae9b07578b3aeebf78fcbb3394810acd9a.tar.xz | |
drm/ttm: remove ttm_bo_vm_insert_huge()
[ Upstream commit 0d979509539ed1df883a30d442177ca7be609565 ]
The huge page functionality in TTM does not work safely because PUD and
PMD entries do not have a special bit.
get_user_pages_fast() considers any page that passed pmd_huge() as
usable:
if (unlikely(pmd_trans_huge(pmd) || pmd_huge(pmd) ||
pmd_devmap(pmd))) {
And vmf_insert_pfn_pmd_prot() unconditionally sets
entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
eg on x86 the page will be _PAGE_PRESENT | PAGE_PSE.
As such gup_huge_pmd() will try to deref a struct page:
head = try_grab_compound_head(pmd_page(orig), refs, flags);
and thus crash.
Thomas further notices that the drivers are not expecting the struct page
to be used by anything - in particular the refcount incr above will cause
them to malfunction.
Thus everything about this is not able to fully work correctly considering
GUP_fast. Delete it entirely. It can return someday along with a proper
PMD/PUD_SPECIAL bit in the page table itself to gate GUP_fast.
Fixes: 314b6580adc5 ("drm/ttm, drm/vmwgfx: Support huge TTM pagefaults")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Reviewed-by: Thomas Hellström <thomas.helllstrom@linux.intel.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
[danvet: Update subject per Thomas' &Christian's review]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/0-v2-a44694790652+4ac-ttm_pmd_jgg@nvidia.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include/drm')
| -rw-r--r-- | include/drm/ttm/ttm_bo_api.h | 3 |
1 files changed, 1 insertions, 2 deletions
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h index f681bbdbc698..36f7eb9d0663 100644 --- a/include/drm/ttm/ttm_bo_api.h +++ b/include/drm/ttm/ttm_bo_api.h @@ -594,8 +594,7 @@ vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo, vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf, pgprot_t prot, - pgoff_t num_prefault, - pgoff_t fault_page_size); + pgoff_t num_prefault); vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf); |