On Tue 03-12-19 11:48:53, Thomas Hellström (VMware) wrote:
From: Thomas Hellstrom thellstrom@vmware.com
TTM graphics buffer objects may, transparently to user-space, move between IO and system memory. When that happens, all PTEs pointing to the old location are zapped before the move and then faulted in again if needed. When that happens, the page protection caching mode- and encryption bits may change and be different from those of struct vm_area_struct::vm_page_prot.
We were using an ugly hack to set the page protection correctly. Fix that and instead use vmf_insert_mixed_prot() and / or vmf_insert_pfn_prot(). Also get the default page protection from struct vm_area_struct::vm_page_prot rather than using vm_get_page_prot(). This way we catch modifications done by the vm system for drivers that want write-notification.
So essentially this should have any new side effect on functionality it is just making a hacky/ugly code less so? In other words what are the consequences of having page protection inconsistent from vma's?
Cc: Andrew Morton akpm@linux-foundation.org Cc: Michal Hocko mhocko@suse.com Cc: "Matthew Wilcox (Oracle)" willy@infradead.org Cc: "Kirill A. Shutemov" kirill.shutemov@linux.intel.com Cc: Ralph Campbell rcampbell@nvidia.com Cc: "Jérôme Glisse" jglisse@redhat.com Cc: "Christian König" christian.koenig@amd.com Signed-off-by: Thomas Hellstrom thellstrom@vmware.com Reviewed-by: Christian König christian.koenig@amd.com
drivers/gpu/drm/ttm/ttm_bo_vm.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c index e6495ca2630b..2098f8d4dfc5 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c @@ -173,7 +173,6 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf, pgoff_t num_prefault) { struct vm_area_struct *vma = vmf->vma;
- struct vm_area_struct cvma = *vma; struct ttm_buffer_object *bo = vma->vm_private_data; struct ttm_bo_device *bdev = bo->bdev; unsigned long page_offset;
@@ -244,7 +243,7 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf, goto out_io_unlock; }
- cvma.vm_page_prot = ttm_io_prot(bo->mem.placement, prot);
- prot = ttm_io_prot(bo->mem.placement, prot); if (!bo->mem.bus.is_iomem) { struct ttm_operation_ctx ctx = { .interruptible = false,
@@ -260,7 +259,7 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf, } } else { /* Iomem should not be marked encrypted */
cvma.vm_page_prot = pgprot_decrypted(cvma.vm_page_prot);
prot = pgprot_decrypted(prot);}
/*
@@ -284,10 +283,11 @@ vm_fault_t ttm_bo_vm_fault_reserved(struct vm_fault *vmf, }
if (vma->vm_flags & VM_MIXEDMAP)
ret = vmf_insert_mixed(&cvma, address,__pfn_to_pfn_t(pfn, PFN_DEV));
ret = vmf_insert_mixed_prot(vma, address,__pfn_to_pfn_t(pfn, PFN_DEV),prot);
ret = vmf_insert_pfn(&cvma, address, pfn);
ret = vmf_insert_pfn_prot(vma, address, pfn, prot);/* Never error on prefaulted PTEs */ if (unlikely((ret & VM_FAULT_ERROR))) {
@@ -319,7 +319,7 @@ vm_fault_t ttm_bo_vm_fault(struct vm_fault *vmf) if (ret) return ret;
- prot = vm_get_page_prot(vma->vm_flags);
- prot = vma->vm_page_prot; ret = ttm_bo_vm_fault_reserved(vmf, prot, TTM_BO_VM_NUM_PREFAULT); if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT)) return ret;
-- 2.21.0