On Wed, Aug 26, 2015 at 04:31:50PM -0400, Jerome Glisse wrote:
On Wed, Aug 26, 2015 at 03:44:52PM -0400, Konrad Rzeszutek Wilk wrote:
On Wed, Aug 26, 2015 at 03:26:42PM -0400, Jerome Glisse wrote:
On Wed, Aug 26, 2015 at 03:02:31PM -0400, Konrad Rzeszutek Wilk wrote:
On Wed, Aug 26, 2015 at 02:52:02PM -0400, jglisse@redhat.com wrote:
From: Jérôme Glisse jglisse@redhat.com
Some device like GPU do things differently if swiotlb is in use. We use to rely on swiotlb_nr_tbl() to know if swiotlb was enabled or not but this is unreliable. Patch add a simple helpers to check if any of
Why is it unreliable?
Alex reported on irc that swiotlb_nr_tbl() returns non zero even if swiotlb is disabled. This seems to be due to ac2cbab21f318e19bc176a7f38a120cec835220f which cleanup swiotlb init and always allocate default size. Which i believe is a waste of memory. So we need to add a real helper to know if swiotlb is in use or not and we should not rely on expectation of some swiotlb value.
Ah right, that patch. That should have been part of the description I believe.
the dma_ops associated with a device points to the swiotlb functions, making swiotlb check reliable for a device.
Signed-off-by: Jérôme Glisse jglisse@redhat.com Cc: Konrad Rzeszutek Wilk konrad.wilk@oracle.com Cc: Alex Deucher alexander.deucher@amd.com Cc: Ben Skeggs bskeggs@redhat.com Cc: Dave Airlie airlied@redhat.com Cc: lkml@vger.kernel.org Cc: Daniel Vetter daniel.vetter@intel.com
include/linux/dma-mapping.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h index ac07ff0..eac911e 100644 --- a/include/linux/dma-mapping.h +++ b/include/linux/dma-mapping.h @@ -314,4 +314,22 @@ static inline int dma_mmap_writecombine(struct device *dev, #define dma_unmap_len_set(PTR, LEN_NAME, VAL) do { } while (0) #endif
+#ifdef CONFIG_SWIOTLB +static inline bool swiotlb_in_use(struct device *dev) +{
- struct dma_map_ops *ops = get_dma_ops(dev);
- return (ops->map_sg == swiotlb_map_sg_attrs ||
ops->unmap_sg == swiotlb_unmap_sg_attrs ||ops->map_page == swiotlb_map_page);That won't work. What if we use xen-swiotlb which has different function names?
I didn't thought about xen, always doing things differently, i think xen is just a matter of also testing for the xen function. I just wanted to have the helper in common code and only rely on common things, instead of having to add a per arch helper.
There has to be a better way. Perhaps you can expand SWIOTLB to actually check if it is in use?
This would require per arch modifications which is what i was trying to avoid.
How? If you modify 'swiotlb_nr_tbl' to return true only if it has been used then the modifications are only in the lib/swiotlb.c ?
Cheers, Jérôme