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| author | Jason Gunthorpe <jgg@nvidia.com> | 2021-10-19 20:27:31 -0300 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2021-11-05 11:13:19 +0100 |
| commit | 0d979509539ed1df883a30d442177ca7be609565 (patch) | |
| tree | 783afaf2a055723bcb4dd927c445eeb1b201a6e6 /drivers/gpu/drm/vmwgfx/vmwgfx_drv.h | |
| parent | ff2d23843f7fb4f13055be5a4a9a20ddd04e6e9c (diff) | |
| download | lwn-0d979509539ed1df883a30d442177ca7be609565.tar.gz lwn-0d979509539ed1df883a30d442177ca7be609565.zip | |
drm/ttm: remove ttm_bo_vm_insert_huge()
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
Diffstat (limited to 'drivers/gpu/drm/vmwgfx/vmwgfx_drv.h')
| -rw-r--r-- | drivers/gpu/drm/vmwgfx/vmwgfx_drv.h | 4 |
1 files changed, 0 insertions, 4 deletions
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h index a833751099b5..858aff99a3fe 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h @@ -1550,10 +1550,6 @@ void vmw_bo_dirty_unmap(struct vmw_buffer_object *vbo, pgoff_t start, pgoff_t end); vm_fault_t vmw_bo_vm_fault(struct vm_fault *vmf); vm_fault_t vmw_bo_vm_mkwrite(struct vm_fault *vmf); -#ifdef CONFIG_TRANSPARENT_HUGEPAGE -vm_fault_t vmw_bo_vm_huge_fault(struct vm_fault *vmf, - enum page_entry_size pe_size); -#endif /* Transparent hugepage support - vmwgfx_thp.c */ #ifdef CONFIG_TRANSPARENT_HUGEPAGE |