Re: [PATCH v5 05/38] drm: prime: use sgtable iterators in drm_prime_sg_to_page_addr_arrays()
Hi Marek,
On Tue, 22 Sep 2020, Marek Szyprowski wrote:
> External email: Use caution opening links or attachments
>
>
> Hi Alex,
>
> On 22.09.2020 01:15, Alex Goins wrote:
> > Tested-by: Alex Goins
> >
> > This change fixes a regression with drm_prime_sg_to_page_addr_arrays() and
> > AMDGPU in v5.9.
>
> Thanks for testing!
>
> > Commit 39913934 similarly revamped AMDGPU to use sgtable helper functions.
> > When
> > it changed from dma_map_sg_attrs() to dma_map_sgtable(), as a side effect it
> > started correctly updating sgt->nents to the return value of
> > dma_map_sg_attrs().
> > However, drm_prime_sg_to_page_addr_arrays() incorrectly uses sgt->nents to
> > iterate over pages, rather than sgt->orig_nents, resulting in it now
> > returning
> > the incorrect number of pages on AMDGPU.
> >
> > I had written a patch that changes drm_prime_sg_to_page_addr_arrays() to use
> > for_each_sgtable_sg() instead of for_each_sg(), iterating using
> > sgt->orig_nents:
> >
> > - for_each_sg(sgt->sgl, sg, sgt->nents, count) {
> > + for_each_sgtable_sg(sgt, sg, count) {
> >
> > This patch takes it further, but still has the effect of fixing the number
> > of
> > pages that drm_prime_sg_to_page_addr_arrays() returns. Something like this
> > should be included in v5.9 to prevent a regression with AMDGPU.
>
> Probably the easiest way to handle a fix for v5.9 would be to simply
> merge the latest version of this patch also to v5.9-rcX:
> https://lore.kernel.org/dri-devel/20200904131711.12950-3-m.szyprow...@samsung.com/
Tested-by: Alex Goins that version too.
>
> This way we would get it fixed and avoid possible conflict in the -next.
> Do you have any AMDGPU fixes for v5.9 in the queue? Maybe you can add that
> patch to the queue?
I don't have any more AMDGPU fixes, just want to ensure that this makes it in.
Thanks,
Alex
> Dave: would it be okay that way?
>
> Best regards
> --
> Marek Szyprowski, PhD
> Samsung R Institute Poland
>
>
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Re: [PATCH v5 05/38] drm: prime: use sgtable iterators in drm_prime_sg_to_page_addr_arrays()
Hi Alex,
On 22.09.2020 01:15, Alex Goins wrote:
> Tested-by: Alex Goins
>
> This change fixes a regression with drm_prime_sg_to_page_addr_arrays() and
> AMDGPU in v5.9.
Thanks for testing!
> Commit 39913934 similarly revamped AMDGPU to use sgtable helper functions.
> When
> it changed from dma_map_sg_attrs() to dma_map_sgtable(), as a side effect it
> started correctly updating sgt->nents to the return value of
> dma_map_sg_attrs().
> However, drm_prime_sg_to_page_addr_arrays() incorrectly uses sgt->nents to
> iterate over pages, rather than sgt->orig_nents, resulting in it now returning
> the incorrect number of pages on AMDGPU.
>
> I had written a patch that changes drm_prime_sg_to_page_addr_arrays() to use
> for_each_sgtable_sg() instead of for_each_sg(), iterating using
> sgt->orig_nents:
>
> - for_each_sg(sgt->sgl, sg, sgt->nents, count) {
> + for_each_sgtable_sg(sgt, sg, count) {
>
> This patch takes it further, but still has the effect of fixing the number of
> pages that drm_prime_sg_to_page_addr_arrays() returns. Something like this
> should be included in v5.9 to prevent a regression with AMDGPU.
Probably the easiest way to handle a fix for v5.9 would be to simply
merge the latest version of this patch also to v5.9-rcX:
https://lore.kernel.org/dri-devel/20200904131711.12950-3-m.szyprow...@samsung.com/
This way we would get it fixed and avoid possible conflict in the -next.
Do you have any AMDGPU fixes for v5.9 in the queue? Maybe you can add
that patch to the queue? Dave: would it be okay that way?
Best regards
--
Marek Szyprowski, PhD
Samsung R Institute Poland
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Re: [PATCH v5 05/38] drm: prime: use sgtable iterators in drm_prime_sg_to_page_addr_arrays()
Tested-by: Alex Goins
This change fixes a regression with drm_prime_sg_to_page_addr_arrays() and
AMDGPU in v5.9.
Commit 39913934 similarly revamped AMDGPU to use sgtable helper functions. When
it changed from dma_map_sg_attrs() to dma_map_sgtable(), as a side effect it
started correctly updating sgt->nents to the return value of dma_map_sg_attrs().
However, drm_prime_sg_to_page_addr_arrays() incorrectly uses sgt->nents to
iterate over pages, rather than sgt->orig_nents, resulting in it now returning
the incorrect number of pages on AMDGPU.
I had written a patch that changes drm_prime_sg_to_page_addr_arrays() to use
for_each_sgtable_sg() instead of for_each_sg(), iterating using sgt->orig_nents:
- for_each_sg(sgt->sgl, sg, sgt->nents, count) {
+ for_each_sgtable_sg(sgt, sg, count) {
This patch takes it further, but still has the effect of fixing the number of
pages that drm_prime_sg_to_page_addr_arrays() returns. Something like this
should be included in v5.9 to prevent a regression with AMDGPU.
Thanks,
Alex
On Wed, 13 May 2020, Marek Szyprowski wrote:
> Replace the current hand-crafted code for extracting pages and DMA
> addresses from the given scatterlist by the much more robust
> code based on the generic scatterlist iterators and recently
> introduced sg_table-based wrappers. The resulting code is simple and
> easy to understand, so the comment describing the old code is no
> longer needed.
>
> Signed-off-by: Marek Szyprowski
> ---
> For more information, see '[PATCH v5 00/38] DRM: fix struct sg_table nents
> vs. orig_nents misuse' thread:
> https://lore.kernel.org/linux-iommu/20200513132114.6046-1-m.szyprow...@samsung.com/T/
> ---
> drivers/gpu/drm/drm_prime.c | 47
> ++---
> 1 file changed, 14 insertions(+), 33 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 1d2e5fe..dfdf4d4 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -985,45 +985,26 @@ struct drm_gem_object *drm_gem_prime_import(struct
> drm_device *dev,
> int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page
> **pages,
>dma_addr_t *addrs, int max_entries)
> {
> - unsigned count;
> - struct scatterlist *sg;
> - struct page *page;
> - u32 page_len, page_index;
> - dma_addr_t addr;
> - u32 dma_len, dma_index;
> + struct sg_dma_page_iter dma_iter;
> + struct sg_page_iter page_iter;
> + struct page **p = pages;
> + dma_addr_t *a = addrs;
>
> - /*
> - * Scatterlist elements contains both pages and DMA addresses, but
> - * one shoud not assume 1:1 relation between them. The sg->length is
> - * the size of the physical memory chunk described by the sg->page,
> - * while sg_dma_len(sg) is the size of the DMA (IO virtual) chunk
> - * described by the sg_dma_address(sg).
> - */
> - page_index = 0;
> - dma_index = 0;
> - for_each_sg(sgt->sgl, sg, sgt->nents, count) {
> - page_len = sg->length;
> - page = sg_page(sg);
> - dma_len = sg_dma_len(sg);
> - addr = sg_dma_address(sg);
> -
> - while (pages && page_len > 0) {
> - if (WARN_ON(page_index >= max_entries))
> + if (pages) {
> + for_each_sgtable_page(sgt, _iter, 0) {
> + if (p - pages >= max_entries)
> return -1;
> - pages[page_index] = page;
> - page++;
> - page_len -= PAGE_SIZE;
> - page_index++;
> + *p++ = sg_page_iter_page(_iter);
> }
> - while (addrs && dma_len > 0) {
> - if (WARN_ON(dma_index >= max_entries))
> + }
> + if (addrs) {
> + for_each_sgtable_dma_page(sgt, _iter, 0) {
> + if (a - addrs >= max_entries)
> return -1;
> - addrs[dma_index] = addr;
> - addr += PAGE_SIZE;
> - dma_len -= PAGE_SIZE;
> - dma_index++;
> + *a++ = sg_page_iter_dma_address(_iter);
> }
> }
> +
> return 0;
> }
> EXPORT_SYMBOL(drm_prime_sg_to_page_addr_arrays);
> --
> 1.9.1
>
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