[PATCH 5.15 794/917] drm/ttm: remove ttm_bo_vm_insert_huge()

Greg Kroah-Hartman
2021-11-16T00:36:38Z

From: Jason Gunthorpe <jgg@nvidia.com>

[ 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>
---
drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c | 2 +-
drivers/gpu/drm/nouveau/nouveau_gem.c | 2 +-
drivers/gpu/drm/radeon/radeon_gem.c | 2 +-
drivers/gpu/drm/ttm/ttm_bo_vm.c | 94 +---------------------
drivers/gpu/drm/vmwgfx/vmwgfx_drv.h | 4 -
drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c | 72 +----------------
drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c | 3 -
include/drm/ttm/ttm_bo_api.h | 3 +-
8 files changed, 7 insertions(+), 175 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
index d6aa032890ee8..a1e63ba4c54a5 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_gem.c
@@ -61,7 +61,7 @@ static vm_fault_t amdgpu_gem_fault(struct vm_fault *vmf)
}

ret = ttm_bo_vm_fault_reserved(vmf, vmf->vma->vm_page_prot,
- TTM_BO_VM_NUM_PREFAULT, 1);
+ TTM_BO_VM_NUM_PREFAULT);

drm_dev_exit(idx);
} else {
diff --git a/drivers/gpu/drm/nouveau/nouveau_gem.c b/drivers/gpu/drm/nouveau/nouveau_gem.c
index 8c2ecc2827232..c89d5964148fd 100644
--- a/drivers/gpu/drm/nouveau/nouveau_gem.c
+++ b/drivers/gpu/drm/nouveau/nouveau_gem.c
@@ -56,7 +56,7 @@ static vm_fault_t nouveau_ttm_fault(struct vm_fault *vmf)

nouveau_bo_del_io_reserve_lru(bo);
prot = vm_get_page_prot(vma->vm_flags);
- ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT, 1);
+ ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
nouveau_bo_add_io_reserve_lru(bo);
if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
return ret;
diff --git a/drivers/gpu/drm/radeon/radeon_gem.c b/drivers/gpu/drm/radeon/radeon_gem.c
index 458f92a708879..a36a4f2c76b09 100644
--- a/drivers/gpu/drm/radeon/radeon_gem.c
+++ b/drivers/gpu/drm/radeon/radeon_gem.c
@@ -61,7 +61,7 @@ static vm_fault_t radeon_gem_fault(struct vm_fault *vmf)
goto unlock_resv;

ret = ttm_bo_vm_fault_reserved(vmf, vmf->vma->vm_page_prot,
- TTM_BO_VM_NUM_PREFAULT, 1);
+ TTM_BO_VM_NUM_PREFAULT);
if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
goto unlock_mclk;

diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c
index 5b9b7fd01a692..4a655ab23c89d 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_vm.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c
@@ -171,89 +171,6 @@ vm_fault_t ttm_bo_vm_reserve(struct ttm_buffer_object *bo,
}
EXPORT_SYMBOL(ttm_bo_vm_reserve);

-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-/**
- * ttm_bo_vm_insert_huge - Insert a pfn for PUD or PMD faults
- * @vmf: Fault data
- * @bo: The buffer object
- * @page_offset: Page offset from bo start
- * @fault_page_size: The size of the fault in pages.
- * @pgprot: The page protections.
- * Does additional checking whether it's possible to insert a PUD or PMD
- * pfn and performs the insertion.
- *
- * Return: VM_FAULT_NOPAGE on successful insertion, VM_FAULT_FALLBACK if
- * a huge fault was not possible, or on insertion error.
- */
-static vm_fault_t ttm_bo_vm_insert_huge(struct vm_fault *vmf,
- struct ttm_buffer_object *bo,
- pgoff_t page_offset,
- pgoff_t fault_page_size,
- pgprot_t pgprot)
-{
- pgoff_t i;
- vm_fault_t ret;
- unsigned long pfn;
- pfn_t pfnt;
- struct ttm_tt *ttm = bo->ttm;
- bool write = vmf->flags & FAULT_FLAG_WRITE;
-
- /* Fault should not cross bo boundary. */
- page_offset &= ~(fault_page_size - 1);
- if (page_offset + fault_page_size > bo->resource->num_pages)
- goto out_fallback;
-
- if (bo->resource->bus.is_iomem)
- pfn = ttm_bo_io_mem_pfn(bo, page_offset);
- else
- pfn = page_to_pfn(ttm->pages[page_offset]);
-
- /* pfn must be fault_page_size aligned. */
- if ((pfn & (fault_page_size - 1)) != 0)
- goto out_fallback;
-
- /* Check that memory is contiguous. */
- if (!bo->resource->bus.is_iomem) {
- for (i = 1; i < fault_page_size; ++i) {
- if (page_to_pfn(ttm->pages[page_offset + i]) != pfn + i)
- goto out_fallback;
- }
- } else if (bo->bdev->funcs->io_mem_pfn) {
- for (i = 1; i < fault_page_size; ++i) {
- if (ttm_bo_io_mem_pfn(bo, page_offset + i) != pfn + i)
- goto out_fallback;
- }
- }
-
- pfnt = __pfn_to_pfn_t(pfn, PFN_DEV);
- if (fault_page_size == (HPAGE_PMD_SIZE >> PAGE_SHIFT))
- ret = vmf_insert_pfn_pmd_prot(vmf, pfnt, pgprot, write);
-#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
- else if (fault_page_size == (HPAGE_PUD_SIZE >> PAGE_SHIFT))
- ret = vmf_insert_pfn_pud_prot(vmf, pfnt, pgprot, write);
-#endif
- else
- WARN_ON_ONCE(ret = VM_FAULT_FALLBACK);
-
- if (ret != VM_FAULT_NOPAGE)
- goto out_fallback;
-
- return VM_FAULT_NOPAGE;
-out_fallback:
- count_vm_event(THP_FAULT_FALLBACK);
- return VM_FAULT_FALLBACK;
-}
-#else
-static vm_fault_t ttm_bo_vm_insert_huge(struct vm_fault *vmf,
- struct ttm_buffer_object *bo,
- pgoff_t page_offset,
- pgoff_t fault_page_size,
- pgprot_t pgprot)
-{
- return VM_FAULT_FALLBACK;
-}
-#endif
-
/**
* ttm_bo_vm_fault_reserved - TTM fault helper
* @vmf: The struct vm_fault given as argument to the fault callback
@@ -261,7 +178,6 @@ static vm_fault_t ttm_bo_vm_insert_huge(struct vm_fault *vmf,
* @num_prefault: Maximum number of prefault pages. The caller may want to
* specify this based on madvice settings and the size of the GPU object
* backed by the memory.
- * @fault_page_size: The size of the fault in pages.
*
* This function inserts one or more page table entries pointing to the
* memory backing the buffer object, and then returns a return code
@@ -275,8 +191,7 @@ static vm_fault_t ttm_bo_vm_insert_huge(struct vm_fault *vmf,
*/
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)
{
struct vm_area_struct *vma = vmf->vma;
struct ttm_buffer_object *bo = vma->vm_private_data;
@@ -327,11 +242,6 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf,
prot = pgprot_decrypted(prot);
}

- /* We don't prefault on huge faults. Yet. */
- if (IS_ENABLED(CONFIG_TRANSPARENT_HUGEPAGE) && fault_page_size != 1)
- return ttm_bo_vm_insert_huge(vmf, bo, page_offset,
- fault_page_size, prot);
-
/*
* Speculatively prefault a number of pages. Only error on
* first page.
@@ -429,7 +339,7 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf)

prot = vma->vm_page_prot;
if (drm_dev_enter(ddev, &idx)) {
- ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT, 1);
+ ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT);
drm_dev_exit(idx);
} else {
ret = ttm_bo_vm_dummy_page(vmf, prot);
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h b/drivers/gpu/drm/vmwgfx/vmwgfx_drv.h
index a833751099b55..858aff99a3fe5 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
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c b/drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c
index e5a9a5cbd01a7..922317d1acc8a 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c
@@ -477,7 +477,7 @@ vm_fault_t vmw_bo_vm_fault(struct vm_fault *vmf)
else
prot = vm_get_page_prot(vma->vm_flags);

- ret = ttm_bo_vm_fault_reserved(vmf, prot, num_prefault, 1);
+ ret = ttm_bo_vm_fault_reserved(vmf, prot, num_prefault);
if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
return ret;

@@ -486,73 +486,3 @@ out_unlock:

return ret;
}
-
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
-vm_fault_t vmw_bo_vm_huge_fault(struct vm_fault *vmf,
- enum page_entry_size pe_size)
-{
- struct vm_area_struct *vma = vmf->vma;
- struct ttm_buffer_object *bo = (struct ttm_buffer_object *)
- vma->vm_private_data;
- struct vmw_buffer_object *vbo =
- container_of(bo, struct vmw_buffer_object, base);
- pgprot_t prot;
- vm_fault_t ret;
- pgoff_t fault_page_size;
- bool write = vmf->flags & FAULT_FLAG_WRITE;
-
- switch (pe_size) {
- case PE_SIZE_PMD:
- fault_page_size = HPAGE_PMD_SIZE >> PAGE_SHIFT;
- break;
-#ifdef CONFIG_HAVE_ARCH_TRANSPARENT_HUGEPAGE_PUD
- case PE_SIZE_PUD:
- fault_page_size = HPAGE_PUD_SIZE >> PAGE_SHIFT;
- break;
-#endif
- default:
- WARN_ON_ONCE(1);
- return VM_FAULT_FALLBACK;
- }
-
- /* Always do write dirty-tracking and COW on PTE level. */
- if (write && (READ_ONCE(vbo->dirty) || is_cow_mapping(vma->vm_flags)))
- return VM_FAULT_FALLBACK;
-
- ret = ttm_bo_vm_reserve(bo, vmf);
- if (ret)
- return ret;
-
- if (vbo->dirty) {
- pgoff_t allowed_prefault;
- unsigned long page_offset;
-
- page_offset = vmf->pgoff -
- drm_vma_node_start(&bo->base.vma_node);
- if (page_offset >= bo->resource->num_pages ||
- vmw_resources_clean(vbo, page_offset,
- page_offset + PAGE_SIZE,
- &allowed_prefault)) {
- ret = VM_FAULT_SIGBUS;
- goto out_unlock;
- }
-
- /*
- * Write protect, so we get a new fault on write, and can
- * split.
- */
- prot = vm_get_page_prot(vma->vm_flags & ~VM_SHARED);
- } else {
- prot = vm_get_page_prot(vma->vm_flags);
- }
-
- ret = ttm_bo_vm_fault_reserved(vmf, prot, 1, fault_page_size);
- if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
- return ret;
-
-out_unlock:
- dma_resv_unlock(bo->base.resv);
-
- return ret;
-}
-#endif
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
index e6b1f98ec99f0..0a4c340252ec4 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_glue.c
@@ -61,9 +61,6 @@ int vmw_mmap(struct file *filp, struct vm_area_struct *vma)
.fault = vmw_bo_vm_fault,
.open = ttm_bo_vm_open,
.close = ttm_bo_vm_close,
-#ifdef CONFIG_TRANSPARENT_HUGEPAGE
- .huge_fault = vmw_bo_vm_huge_fault,
-#endif
};
struct drm_file *file_priv = filp->private_data;
struct vmw_private *dev_priv = vmw_priv(file_priv->minor->dev);
diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index f681bbdbc6982..36f7eb9d06639 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);

--
2.33.0