From: Marek Szyprowski <m.szyprowski@samsung.com>
To: "Christian König" <christian.koenig@amd.com>,
"Shane Francis" <bigbeeshane@gmail.com>,
dri-devel@lists.freedesktop.org
Cc: airlied@linux.ie, linux-kernel@vger.kernel.org,
amd-gfx-request@lists.freedesktop.org, alexander.deucher@amd.com
Subject: Re: [v4,1/3] drm/prime: use dma length macro when mapping sg
Date: Fri, 27 Mar 2020 10:10:52 +0100 [thread overview]
Message-ID: <cd773011-969b-28df-7488-9fddae420d81@samsung.com> (raw)
In-Reply-To: <82df6735-1cf0-e31f-29cc-f7d07bdaf346@amd.com>
Hi Christian,
On 2020-03-27 09:11, Christian König wrote:
> Am 27.03.20 um 08:54 schrieb Marek Szyprowski:
>> On 2020-03-25 10:07, Shane Francis wrote:
>>> As dma_map_sg can reorganize scatter-gather lists in a
>>> way that can cause some later segments to be empty we should
>>> always use the sg_dma_len macro to fetch the actual length.
>>>
>>> This could now be 0 and not need to be mapped to a page or
>>> address array
>>>
>>> Signed-off-by: Shane Francis <bigbeeshane@gmail.com>
>>> Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
>> This patch landed in linux-next 20200326 and it causes a kernel panic on
>> various Exynos SoC based boards.
>>> ---
>>> drivers/gpu/drm/drm_prime.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
>>> index 86d9b0e45c8c..1de2cde2277c 100644
>>> --- a/drivers/gpu/drm/drm_prime.c
>>> +++ b/drivers/gpu/drm/drm_prime.c
>>> @@ -967,7 +967,7 @@ int drm_prime_sg_to_page_addr_arrays(struct
>>> sg_table *sgt, struct page **pages,
>>> index = 0;
>>> for_each_sg(sgt->sgl, sg, sgt->nents, count) {
>>> - len = sg->length;
>>> + len = sg_dma_len(sg);
>>> page = sg_page(sg);
>>> addr = sg_dma_address(sg);
>> Sorry, but this code is wrong :(
>
> Well it is at least better than before because it makes most drivers
> work correctly again.
Well, I'm not sure that a half-broken fix should be considered as a fix ;)
Anyway, I just got the comment from Shane, that my patch is fixing the
issues with amdgpu and radeon, while still working fine for exynos, so
it is indeed a proper fix.
> See we only fill the pages array because some drivers (like Exynos)
> are still buggy and require this.
Exynos driver use this pages array internally.
>
> Accessing the pages of an DMA-buf imported sg_table is illegal and
> should be fixed in the drivers.
True, but in meantime we should avoid breaking stuff which worked fine
for ages.
>
>> [SNIP]
>>
>> I will send a patch in a few minutes with the above fixed code.
>
> That is certainly a good idea for now, but could we also put on
> somebodies todo list an item to fix Exynos?
Yes, I can take a look into removing the use of the internal pages
array. It is used mainly for implementing vmap for fbdev emulation, but
this can be handled in a different way.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
next prev parent reply other threads:[~2020-03-27 9:11 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-25 9:07 [PATCH v4 0/3] AMDGPU / RADEON / DRM Fix mapping of user pages Shane Francis
2020-03-25 9:07 ` [PATCH v4 1/3] drm/prime: use dma length macro when mapping sg Shane Francis
2020-03-25 13:56 ` Ruhl, Michael J
[not found] ` <CGME20200327075458eucas1p2f1011560c5d2d2a754d2394f56367ebb@eucas1p2.samsung.com>
2020-03-27 7:54 ` [v4,1/3] " Marek Szyprowski
2020-03-27 8:11 ` Christian König
2020-03-27 9:10 ` Marek Szyprowski [this message]
2020-03-30 8:18 ` Marek Szyprowski
2020-03-30 9:39 ` Shane Francis
2020-03-30 12:32 ` Shane Francis
2020-03-30 12:34 ` Shane Francis
2020-03-30 13:23 ` Alex Deucher
2020-03-31 5:25 ` Marek Szyprowski
2020-03-31 14:10 ` Alex Deucher
2020-03-31 14:29 ` Marek Szyprowski
[not found] ` <CGME20200327082702eucas1p1a66dd059480c9d02b8f0f3ab225db2c3@eucas1p1.samsung.com>
2020-03-27 8:26 ` Marek Szyprowski
2020-03-25 9:07 ` [PATCH v4 2/3] drm/amdgpu: fix scatter-gather mapping with user pages Shane Francis
2020-03-25 14:00 ` Ruhl, Michael J
2020-03-25 9:07 ` [PATCH v4 3/3] drm/radeon: " Shane Francis
2020-03-25 14:19 ` Ruhl, Michael J
2020-03-25 15:54 ` Shane Francis
2020-03-25 16:08 ` Alex Deucher
2020-03-25 13:11 ` [PATCH v4 0/3] AMDGPU / RADEON / DRM Fix mapping of " Ruhl, Michael J
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=cd773011-969b-28df-7488-9fddae420d81@samsung.com \
--to=m.szyprowski@samsung.com \
--cc=airlied@linux.ie \
--cc=alexander.deucher@amd.com \
--cc=amd-gfx-request@lists.freedesktop.org \
--cc=bigbeeshane@gmail.com \
--cc=christian.koenig@amd.com \
--cc=dri-devel@lists.freedesktop.org \
--cc=linux-kernel@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).