Re: [PATCH v4 5/9] drm/ttm, drm/vmwgfx: Support huge TTM pagefaults

On Thu, 20 Feb 2020 13:27:15 +0100 Thomas Hellstrom wrote:

+static vm_fault_t ttm_bo_vm_huge_fault(struct vm_fault *vmf,

• 		       enum page_entry_size pe_size)
  

+{

• struct vm_area_struct *vma = vmf->vma;
• pgprot_t prot;
• struct ttm_buffer_object *bo = vma->vm_private_data;
• vm_fault_t ret;
• pgoff_t fault_page_size = 0;
• 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;
  

• }
• /* Fallback on write dirty-tracking or COW */
• if (write && ttm_pgprot_is_wrprotecting(vma->vm_page_prot))

• return VM_FAULT_FALLBACK;
  

• ret = ttm_bo_vm_reserve(bo, vmf);
• if (ret)

• return ret;
  

• 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;
  

Seems it does not make much sense to check VM_FAULT_RETRY and return as at least resv lock is left behind without care.

• dma_resv_unlock(bo->base.resv);
• return ret;

+}