[bug report] drm/vmwgfx: Implement an infrastructure for read-coherent resources

[Dan Carpenter]

Huh... Vmware is blocking email to Thomas?

"Recipient is not authorized to accept external mail"

This seems like potentially a serious bug and I don't know how to report
it.

regards,
dan carpenter

On Thu, Jul 29, 2021 at 05:39:45PM +0300, Dan Carpenter wrote:
> Hello Thomas Hellstrom,
> 
> The patch fb80edb0d766: "drm/vmwgfx: Implement an infrastructure for
> read-coherent resources" from Mar 28, 2019, leads to the following
> static checker warning:
> 
> 	drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c:461 vmw_bo_vm_fault()
> 	warn: missing conversion: 'page_offset + ((1) << 12)' 'page + byte'
> 
> 	drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c:534 vmw_bo_vm_huge_fault()
> 	warn: missing conversion: 'page_offset + ((1) << 12)' 'page + byte'
> 
> drivers/gpu/drm/vmwgfx/vmwgfx_page_dirty.c
>     435 vm_fault_t vmw_bo_vm_fault(struct vm_fault *vmf)
>     436 {
>     437 	struct vm_area_struct *vma = vmf->vma;
>     438 	struct ttm_buffer_object *bo = (struct ttm_buffer_object *)
>     439 	    vma->vm_private_data;
>     440 	struct vmw_buffer_object *vbo =
>     441 		container_of(bo, struct vmw_buffer_object, base);
>     442 	pgoff_t num_prefault;
>     443 	pgprot_t prot;
>     444 	vm_fault_t ret;
>     445 
>     446 	ret = ttm_bo_vm_reserve(bo, vmf);
>     447 	if (ret)
>     448 		return ret;
>     449 
>     450 	num_prefault = (vma->vm_flags & VM_RAND_READ) ? 1 :
>     451 		TTM_BO_VM_NUM_PREFAULT;
>     452 
>     453 	if (vbo->dirty) {
>     454 		pgoff_t allowed_prefault;
>     455 		unsigned long page_offset;
>     456 
>     457 		page_offset = vmf->pgoff -
>     458 			drm_vma_node_start(&bo->base.vma_node);
>     459 		if (page_offset >= bo->resource->num_pages ||
>                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> page_offset is in terms of pages
> 
>     460 		    vmw_resources_clean(vbo, page_offset,
> --> 461 					page_offset + PAGE_SIZE,
>                                                 ^^^^^^^^^^^^^^^^^^^^^^^
> It doesn't make sense to add PAGE_SIZE (which is bytes) to pages.  The
> code in vmw_bo_vm_huge_fault() has a similar bug.
> 
>     462 					&allowed_prefault)) {
>     463 			ret = VM_FAULT_SIGBUS;
>     464 			goto out_unlock;
>     465 		}
>     466 
>     467 		num_prefault = min(num_prefault, allowed_prefault);
>     468 	}
>     469 
>     470 	/*
>     471 	 * If we don't track dirty using the MKWRITE method, make sure
>     472 	 * sure the page protection is write-enabled so we don't get
>     473 	 * a lot of unnecessary write faults.
>     474 	 */
>     475 	if (vbo->dirty && vbo->dirty->method == VMW_BO_DIRTY_MKWRITE)
>     476 		prot = vm_get_page_prot(vma->vm_flags & ~VM_SHARED);
>     477 	else
>     478 		prot = vm_get_page_prot(vma->vm_flags);
>     479 
>     480 	ret = ttm_bo_vm_fault_reserved(vmf, prot, num_prefault, 1);
>     481 	if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
>     482 		return ret;
>     483 
>     484 out_unlock:
>     485 	dma_resv_unlock(bo->base.resv);
>     486 
>     487 	return ret;
>     488 }
> 
> regards,
> dan carpenter