Re: [PATCH v7 06/15] drm/ttm: Add a generic TTM memcpy move for page-based iomem

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 




On 5/31/21 2:36 PM, Christian König wrote:
Am 31.05.21 um 14:19 schrieb Thomas Hellström:
The internal ttm_bo_util memcpy uses ioremap functionality, and while it
probably might be possible to use it for copying in- and out of
sglist represented io memory, using io_mem_reserve() / io_mem_free()
callbacks, that would cause problems with fault().
Instead, implement a method mapping page-by-page using kmap_local()
semantics. As an additional benefit we then avoid the occasional global
TLB flushes of ioremap() and consuming ioremap space, elimination of a
critical point of failure and with a slight change of semantics we could
also push the memcpy out async for testing and async driver development
purposes.

A special linear iomem iterator is introduced internally to mimic the
old ioremap behaviour for code-paths that can't immediately be ported
over. This adds to the code size and should be considered a temporary
solution.

Looking at the code we have a lot of checks for iomap tagged pointers.
Ideally we should extend the core memremap functions to also accept
uncached memory and kmap_local functionality. Then we could strip a
lot of code.

Cc: Christian König <christian.koenig@xxxxxxx>
Signed-off-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>
---
v3:
- Split up in various TTM files and addressed review comments by
   Christian König. Tested and fixed legacy iomap memcpy path on i915.
v4:
- Fix an uninitialized variable
   Reported by: kernel test robot <lkp@xxxxxxxxx>
   Reported by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
- Minor change to the ttm_move_memcpy() interface.
- Gracefully handle lack of memremap() support on memcpy
   (Reported by Matthew Auld)
- Minor style fix (Reported by Matthew Auld)
---
  drivers/gpu/drm/ttm/ttm_bo_util.c  | 280 ++++++++++-------------------
  drivers/gpu/drm/ttm/ttm_module.c   |  35 ++++
  drivers/gpu/drm/ttm/ttm_resource.c | 193 ++++++++++++++++++++
  drivers/gpu/drm/ttm/ttm_tt.c       |  42 +++++
  include/drm/ttm/ttm_bo_driver.h    |  28 +++
  include/drm/ttm/ttm_caching.h      |   2 +
  include/drm/ttm/ttm_kmap_iter.h    |  61 +++++++
  include/drm/ttm/ttm_resource.h     |  61 +++++++
  include/drm/ttm/ttm_tt.h           |  16 ++
  9 files changed, 536 insertions(+), 182 deletions(-)
  create mode 100644 include/drm/ttm/ttm_kmap_iter.h

diff --git a/drivers/gpu/drm/ttm/ttm_bo_util.c b/drivers/gpu/drm/ttm/ttm_bo_util.c
index ae8b61460724..6ac7744a1a5c 100644
--- a/drivers/gpu/drm/ttm/ttm_bo_util.c
+++ b/drivers/gpu/drm/ttm/ttm_bo_util.c
@@ -72,190 +72,126 @@ void ttm_mem_io_free(struct ttm_device *bdev,
      mem->bus.addr = NULL;
  }
  -static int ttm_resource_ioremap(struct ttm_device *bdev,
-                   struct ttm_resource *mem,
-                   void **virtual)
+/**
+ * ttm_move_memcpy - Helper to perform a memcpy ttm move operation.
+ * @bo: The struct ttm_buffer_object.
+ * @new_mem: The struct ttm_resource we're moving to (copy destination). + * @new_iter: A struct ttm_kmap_iter representing the destination resource.
+ * @src_iter: A struct ttm_kmap_iter representing the source resource.
+ *
+ * This function is intended to be able to move out async under a
+ * dma-fence if desired.
+ */
+void ttm_move_memcpy(struct ttm_buffer_object *bo,
+             pgoff_t num_pages,

Can we switch to uint32_t for num_pages for TTM in general?

That allows to copy 16TiB when you have 4KiB pages which should be enough for quite a while and I had some really bad bugs because people tend to do << PAGE_SHIFT and forget that it is only 32bit sometimes.

I can do that, although IIRC we've had some discussions internally that 16TiB isn't enough for our bos in general, so at some point a request from us might to be to see what we can do to bump that across TTM for 64-bit?

Matthew, you looked at this a couple of weeks ago?



Apart from that feel free to stick my rb on the patch.

Thanks!

/Thomas



Christian.




[Index of Archives]     [Linux DRI Users]     [Linux Intel Graphics]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [XFree86]     [Linux USB Devel]     [Video for Linux]     [Linux Audio Users]     [Linux Kernel]     [Linux SCSI]     [XFree86]
  Powered by Linux