On 04/17/2015 02:26 PM, Alexandre Courbot wrote:
On Thu, Apr 16, 2015 at 8:06 PM, Vince Hsu <[email protected]> wrote:
Some platforms have IOMMU to map non-contiguous physical memory into
contiguous GPU virtual address. We can use this feature to enable big pages
mapping on scattered small pages. To achieve that, we also need changes in
subdev/mmu as well.
Signed-off-by: Vince Hsu <[email protected]>
---
drm/nouveau/nouveau_bo.c | 9 +++++++++
1 file changed, 9 insertions(+)
diff --git a/drm/nouveau/nouveau_bo.c b/drm/nouveau/nouveau_bo.c
index 77326e344dad..da76ee1121e4 100644
--- a/drm/nouveau/nouveau_bo.c
+++ b/drm/nouveau/nouveau_bo.c
@@ -221,6 +221,11 @@ nouveau_bo_new(struct drm_device *dev, int size, int align,
if (drm->client.vm) {
if (!(flags & TTM_PL_FLAG_TT) && size > 256 * 1024)
nvbo->page_shift = drm->client.vm->mmu->lpg_shift;
+
+ if ((flags & TTM_PL_FLAG_TT) &&
+ drm->client.vm->mmu->iommu_capable &&
+ (size % (1 << drm->client.vm->mmu->lpg_shift))
== 0)
+ nvbo->page_shift = drm->client.vm->mmu->lpg_shift;
I wonder if we should not just use the same size heuristics as for VRAM above?
Here, unless your buffer size is an exact multiple of the big page
size (128K for GK20A), you will not use big pages at all. In effect,
many buffers will be rejected for this reason. A behavior like "if the
buffer size of more than 256KB, increase the size of the buffer to the
next multiple of 128K and use big pages" would probably yield better
results.
I'm told that the user space would align the buffer to the big page
size. So I made this patch based on that impression. I'm not pretty
familiar with the user space behavior, so sorry if I say something wrong
here.
And are we allowed to extend the buffer size even the exporter doesn't
know about that?
}
nouveau_bo_fixup_align(nvbo, flags, &align, &size);
@@ -1641,6 +1646,10 @@ nouveau_bo_vma_add(struct nouveau_bo *nvbo, struct
nvkm_vm *vm,
(nvbo->bo.mem.mem_type == TTM_PL_VRAM ||
nvbo->page_shift != vma->vm->mmu->lpg_shift))
nvkm_vm_map(vma, nvbo->bo.mem.mm_node);
+ else if (nvbo->bo.mem.mem_type == TTM_PL_TT &&
+ vma->vm->mmu->iommu_capable &&
+ nvbo->page_shift == vma->vm->mmu->lpg_shift)
+ nvkm_vm_map(vma, nvbo->bo.mem.mm_node);
Sorry, I don't understand why this is needed, could you explain?
Originally the buffer can only be mapped when the memory type is VRAM or
the page is small. So I added another condition to map big page for TT.
Thanks,
Vince
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