On 01/07/2014 10:14 AM, Daniel Vetter wrote:
On Fri, Jan 03, 2014 at 11:22:17AM +0100, Thomas Hellstrom wrote:
This is illegal for at least two reasons:
- While it may work on some platforms / iommus, obtaining page pointers from
mapped sg-lists is illegal, since the DMA API allows page pointer information to be destroyed in the sg mapping process.
- TTM has no way of determining the linear kernel map caching state of the
underlying pages. PTEs with conflicting caching state pointing to the same pfn is not allowed.
TTM operations touching pages of imported sg-tables should be redirected through the proper dma-buf operations.
Signed-off-by: Thomas Hellstrom thellstrom@vmware.com
Shouldn't we do something similar in the kmap helpers ttm_bo_util.c like ttm_bo_kmap and ttm_bo_move_memcpy? Maybe just a BUG to catch driver bugs. Otherwise this sounds like the right thing to do, so Acked. -Daniel
Indeed, although I think that TTM should by default reroute the ttm_bo_kmap operations through the correct dma-buf ops. Haven't gotten around to do that yet.
/Thomas
drivers/gpu/drm/ttm/ttm_bo_vm.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/drivers/gpu/drm/ttm/ttm_bo_vm.c b/drivers/gpu/drm/ttm/ttm_bo_vm.c index cdda784..12d7f53 100644 --- a/drivers/gpu/drm/ttm/ttm_bo_vm.c +++ b/drivers/gpu/drm/ttm/ttm_bo_vm.c @@ -132,6 +132,15 @@ static int ttm_bo_vm_fault(struct vm_area_struct *vma, struct vm_fault *vmf) return VM_FAULT_NOPAGE; }
- /*
* Refuse to fault imported pages. This should be handled* (if at all) by redirecting mmap to the exporter.*/- if (bo->ttm && (bo->ttm->page_flags & TTM_PAGE_FLAG_SG)) {
retval = VM_FAULT_SIGBUS;goto out_unlock;- }
- if (bdev->driver->fault_reserve_notify) { ret = bdev->driver->fault_reserve_notify(bo); switch (ret) {
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