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<div class="moz-cite-prefix">On 2024-01-29 11:30, Christian König
wrote:<br>
</div>
<blockquote type="cite" cite="mid:adb1a9d0-11ff-44c7-9d5d-c20d1bb7f01b@amd.com">Am
29.01.24 um 17:25 schrieb Philip Yang:
<br>
<blockquote type="cite">On 2024-01-29 05:06, Christian König
wrote:
<br>
<blockquote type="cite">Am 26.01.24 um 20:47 schrieb Philip
Yang:
<br>
<blockquote type="cite">This is to work around a bug in
function drm_prime_pages_to_sg if length
<br>
of nr_pages >= 4GB, by doing the same check for
max_segment and then
<br>
calling sg_alloc_table_from_pages_segment directly instead.
<br>
<br>
This issue shows up on APU because VRAM is allocated as GTT
memory. It
<br>
also fixes >=4GB GTT memory mapping for mGPUs with IOMMU
isolation mode.
<br>
</blockquote>
<br>
Well that was talked about before and rejected. If we really
want more than 4GiB in DMA-bufs we need to fix
drm_prime_pages_to_sg() instead.
<br>
</blockquote>
<br>
I sent a patch to fix drm_prime_pages_to_sg but the patch was
rejected.
<br>
<br>
</blockquote>
<br>
Why was that rejected? If this isn't something we want for DRM we
probably don't want it for AMDGPU either.
<br>
</blockquote>
<p>The reason is same as your concern, to check if we want more than
4GB dmabuf support and may need fix for other drm functions.</p>
<p>I am not familiar with drm layer, amdgpu need more than 4GB
dmabuf on mGPUs APU. Do you want me to resend that drm patch to
fix only drm_prime_pages_to_sg function?</p>
<p>anything like this will cause size becomes 0 if nr_pages size is
more than 4GB:<br>
</p>
<p>unsigned int nr_pages;</p>
<p>unsigned long size = nr_pages << PAGE_SHIFT;<br>
</p>
<p>Regards,</p>
<p>Philip<br>
</p>
<blockquote type="cite" cite="mid:adb1a9d0-11ff-44c7-9d5d-c20d1bb7f01b@amd.com">
<br>
<blockquote type="cite">This issue happens on APU, as VRAM is
allocated as GTT memory, get to this patch only if IOMMU is
isolation mode, with IOMMU off or pt mode, multiple GPUs share
the same dma mapping.
<br>
<br>
Even with the fix patch accepted by drm, we still need this
patch to workaround the issue on old kernel version.
<br>
<br>
</blockquote>
<br>
Yeah, but that's then just a functions fixup for our backporting
team and shouldn't be worked around like this.
<br>
<br>
Regards,
<br>
Christian.
<br>
<br>
<blockquote type="cite">Regards,
<br>
<br>
Philip
<br>
<br>
<blockquote type="cite">
<br>
Regards,
<br>
Christian.
<br>
<br>
<blockquote type="cite">
<br>
Signed-off-by: Philip Yang <a class="moz-txt-link-rfc2396E" href="mailto:Philip.Yang@amd.com"><Philip.Yang@amd.com></a>
<br>
---
<br>
drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 50
++++++++++++++-------
<br>
1 file changed, 34 insertions(+), 16 deletions(-)
<br>
<br>
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
<br>
index 055ba2ea4c12..a203633fd629 100644
<br>
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
<br>
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
<br>
@@ -171,18 +171,41 @@ static struct sg_table
*amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
<br>
}
<br>
switch (bo->tbo.resource->mem_type) {
<br>
- case TTM_PL_TT:
<br>
- sgt = drm_prime_pages_to_sg(obj->dev,
<br>
- bo->tbo.ttm->pages,
<br>
- bo->tbo.ttm->num_pages);
<br>
- if (IS_ERR(sgt))
<br>
- return sgt;
<br>
-
<br>
- if (dma_map_sgtable(attach->dev, sgt, dir,
<br>
- DMA_ATTR_SKIP_CPU_SYNC))
<br>
- goto error_free;
<br>
- break;
<br>
+ case TTM_PL_TT: {
<br>
+ size_t max_segment = 0;
<br>
+ u64 num_pages;
<br>
+ int err;
<br>
+
<br>
+ sgt = kmalloc(sizeof(*sgt), GFP_KERNEL);
<br>
+ if (!sgt)
<br>
+ return ERR_PTR(-ENOMEM);
<br>
+
<br>
+ if (obj->dev)
<br>
+ max_segment =
dma_max_mapping_size(obj->dev->dev);
<br>
+ if (max_segment == 0)
<br>
+ max_segment = UINT_MAX;
<br>
+
<br>
+ /*
<br>
+ * Use u64, otherwise if length of num_pages >=
4GB then size
<br>
+ * (num_pages << PAGE_SHIFT) becomes 0
<br>
+ */
<br>
+ num_pages = bo->tbo.ttm->num_pages;
<br>
+ err = sg_alloc_table_from_pages_segment(sgt,
bo->tbo.ttm->pages,
<br>
+ num_pages, 0,
<br>
+ num_pages << PAGE_SHIFT,
<br>
+ max_segment, GFP_KERNEL);
<br>
+ if (err) {
<br>
+ kfree(sgt);
<br>
+ return ERR_PTR(err);
<br>
+ }
<br>
+ if (dma_map_sgtable(attach->dev, sgt, dir,
DMA_ATTR_SKIP_CPU_SYNC)) {
<br>
+ sg_free_table(sgt);
<br>
+ kfree(sgt);
<br>
+ return ERR_PTR(-EBUSY);
<br>
+ }
<br>
+ break;
<br>
+ }
<br>
case TTM_PL_VRAM:
<br>
r = amdgpu_vram_mgr_alloc_sgt(adev,
bo->tbo.resource, 0,
<br>
bo->tbo.base.size,
attach->dev,
<br>
@@ -195,11 +218,6 @@ static struct sg_table
*amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
<br>
}
<br>
return sgt;
<br>
-
<br>
-error_free:
<br>
- sg_free_table(sgt);
<br>
- kfree(sgt);
<br>
- return ERR_PTR(-EBUSY);
<br>
}
<br>
/**
<br>
</blockquote>
<br>
</blockquote>
</blockquote>
<br>
</blockquote>
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