Re: [RFC][PATCH 0/2] dma-buf: add importer private data for reimporting
On Wed, Jun 05, 2013 at 11:52:59AM +0900, 김승우 wrote:
>
>
> On 2013년 06월 04일 21:55, Daniel Vetter wrote:
> > On Tue, Jun 04, 2013 at 07:42:22PM +0900, 김승우 wrote:
> >>
> >>
> >> On 2013년 06월 01일 00:29, Daniel Vetter wrote:
> >>> On Fri, May 31, 2013 at 07:22:24PM +0900, 김승우 wrote:
> Hello Daniel,
>
> Thanks for your comment.
>
> On 2013년 05월 31일 18:14, Daniel Vetter wrote:
> > On Fri, May 31, 2013 at 10:54 AM, Seung-Woo Kim
> > wrote:
> >> importer private data in dma-buf attachment can be used by importer to
> >> reimport same dma-buf.
> >>
> >> Seung-Woo Kim (2):
> >> dma-buf: add importer private data to attachment
> >> drm/prime: find gem object from the reimported dma-buf
> >
> > Self-import should already work (at least with the latest refcount
> > fixes merged). At least the tests to check both re-import on the same
> > drm fd and on a different all work as expected now.
>
> Currently, prime works well for all case including self-importing,
> importing, and reimporting as you describe. Just, importing dma-buf from
> other driver twice with different drm_fd, each import create its own gem
> object even two import is done for same buffer because prime_priv is in
> struct drm_file. This means mapping to the device is done also twice.
> IMHO, these duplicated creations and maps are not necessary if drm can
> find previous import in different prime_priv.
> >>>
> >>> Well, that's imo a bug with the other driver. If it doesn't export
> >>> something really simple (e.g. contiguous memory which doesn't require any
> >>> mmio resources at all) it should have a cache of exported dma_buf fds so
> >>> that it hands out the same dma_buf every time.
> >>
> >> Hm, all existing dma-buf exporter including i915 driver implements its
> >> map_dma_buf callback as allocating scatter-gather table with pages in
> >> its buffer and calling dma_map_sg() with the sgt. With different
> >> drm_fds, importing one dma-buf *twice*, then importer calls
> >> dma_buf_attach() and dma_buf_map_attachment() twice at least in drm
> >> importer because re-importing case can only checked with prime_priv in
> >> drm_file as I described.
> >
> > Well, but thanks to all the self-import and re-import checks, it's
> > _impossible_ to import the same dma_buf twice without noticing (presuming
> > both importer and exporter are drm devices).
>
> No, it is possible. Prime function, drm_gem_prime_fd_to_handle(), checks
> re-import with following code.
>
> ret = drm_prime_lookup_buf_handle(&file_priv->prime,
> dma_buf, handle);
>
> Unfortunately, file_priv is allocated per each open of drm node so this
> code can only find re-import within same drm open context.
>
> And driver specific import functions, like drm_gem_prime_import(), only
> check self-import like following code.
>
> if (dma_buf->ops == &drm_gem_prime_dmabuf_ops) {
> obj = dma_buf->priv;
> if (obj->dev == dev) {
> /* ... */
> }
> }
>
> This means some application like following can make re-import to
> different gem objects.
>
> int drm_fd1, drm_fd2, ret;
> int dma_buf_fd;
> struct drm_prime_handle prime1, prime2;
>
> drm_fd1 = open(DRM_NODE, O_RDWR, 0);
> drm_fd2 = open(DRM_NODE, O_RDWR, 0);
>
> /* get some dma-buf_fd from other dma-buf exporter */
> prime1.fd = dma_buf_fd;
> prime2.fd = dma_buf_fd;
>
> ret = ioctl(drm_fd1, DRM_IOCTL_PRIME_FD_TO_HANDLE, &prime1);
> ret = ioctl(drm_fd2, DRM_IOCTL_PRIME_FD_TO_HANDLE, &prime2);
>
> This will import same dma-buf twice as different GEM object because
> above checking codes can not check already imported gem object from the
> dma-buf.
Oh right, now I understand. Somehow I've always thought we already take
care of this case, since I remember discussing it.
To fix that we need a device-global import cache similar to how we already
have one for each file_priv. I think we can reuse the same locking and
refcounting scheme, but I haven't checked. The commit messages of the past
few prime changes have fairly good explanations of the tricky stuff going
on there.
Sorry for being dense for so long, I should have checked my idea of what
the drm prime code does with reality sooner ;-)
Cheers, Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
--
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More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC][PATCH 0/2] dma-buf: add importer private data for reimporting
On 2013년 06월 04일 21:55, Daniel Vetter wrote:
> On Tue, Jun 04, 2013 at 07:42:22PM +0900, 김승우 wrote:
>>
>>
>> On 2013년 06월 01일 00:29, Daniel Vetter wrote:
>>> On Fri, May 31, 2013 at 07:22:24PM +0900, 김승우 wrote:
Hello Daniel,
Thanks for your comment.
On 2013년 05월 31일 18:14, Daniel Vetter wrote:
> On Fri, May 31, 2013 at 10:54 AM, Seung-Woo Kim
> wrote:
>> importer private data in dma-buf attachment can be used by importer to
>> reimport same dma-buf.
>>
>> Seung-Woo Kim (2):
>> dma-buf: add importer private data to attachment
>> drm/prime: find gem object from the reimported dma-buf
>
> Self-import should already work (at least with the latest refcount
> fixes merged). At least the tests to check both re-import on the same
> drm fd and on a different all work as expected now.
Currently, prime works well for all case including self-importing,
importing, and reimporting as you describe. Just, importing dma-buf from
other driver twice with different drm_fd, each import create its own gem
object even two import is done for same buffer because prime_priv is in
struct drm_file. This means mapping to the device is done also twice.
IMHO, these duplicated creations and maps are not necessary if drm can
find previous import in different prime_priv.
>>>
>>> Well, that's imo a bug with the other driver. If it doesn't export
>>> something really simple (e.g. contiguous memory which doesn't require any
>>> mmio resources at all) it should have a cache of exported dma_buf fds so
>>> that it hands out the same dma_buf every time.
>>
>> Hm, all existing dma-buf exporter including i915 driver implements its
>> map_dma_buf callback as allocating scatter-gather table with pages in
>> its buffer and calling dma_map_sg() with the sgt. With different
>> drm_fds, importing one dma-buf *twice*, then importer calls
>> dma_buf_attach() and dma_buf_map_attachment() twice at least in drm
>> importer because re-importing case can only checked with prime_priv in
>> drm_file as I described.
>
> Well, but thanks to all the self-import and re-import checks, it's
> _impossible_ to import the same dma_buf twice without noticing (presuming
> both importer and exporter are drm devices).
No, it is possible. Prime function, drm_gem_prime_fd_to_handle(), checks
re-import with following code.
ret = drm_prime_lookup_buf_handle(&file_priv->prime,
dma_buf, handle);
Unfortunately, file_priv is allocated per each open of drm node so this
code can only find re-import within same drm open context.
And driver specific import functions, like drm_gem_prime_import(), only
check self-import like following code.
if (dma_buf->ops == &drm_gem_prime_dmabuf_ops) {
obj = dma_buf->priv;
if (obj->dev == dev) {
/* ... */
}
}
This means some application like following can make re-import to
different gem objects.
int drm_fd1, drm_fd2, ret;
int dma_buf_fd;
struct drm_prime_handle prime1, prime2;
drm_fd1 = open(DRM_NODE, O_RDWR, 0);
drm_fd2 = open(DRM_NODE, O_RDWR, 0);
/* get some dma-buf_fd from other dma-buf exporter */
prime1.fd = dma_buf_fd;
prime2.fd = dma_buf_fd;
ret = ioctl(drm_fd1, DRM_IOCTL_PRIME_FD_TO_HANDLE, &prime1);
ret = ioctl(drm_fd2, DRM_IOCTL_PRIME_FD_TO_HANDLE, &prime2);
This will import same dma-buf twice as different GEM object because
above checking codes can not check already imported gem object from the
dma-buf.
>>
>>>
>>> Or it needs to be more clever in it's dma_buf_attachment_map functions and
>>> lookup up a pre-existing iommu mapping.
>>>
>>> But dealing with this in the importer is just broken.
>>>
> Second, the dma_buf_attachment is _definitely_ the wrong place to do
> this. If you need iommu mapping caching, that should happen at a lower
> level (i.e. in the map_attachment callback somewhere of the exporter,
> that's what the priv field in the attachment is for). Snatching away
> the attachement from some random other import is certainly not the way
> to go - attachements are _not_ refcounted!
Yes, attachments do not have refcount, so importer should handle and drm
case in my patch, importer private data is gem object and it has, of
course, refcount.
And at current, exporter can not classify map_dma_buf requests of same
importer to same buffer with different attachment because dma_buf_attach
always makes new attachments. To resolve this exporter should search all
different attachment from same importer of dma-buf and it seems more
complex than importer private data to me.
If I misunderstood something, please let me know.
>>>
>>> Like I've said above, just fix this in the exporter. If an importer sees
>>> two different dma_bufs it can very well presume that it those two indeed
>>> point to different backing storage.
>>
>> Yes, my patch does not break this concept. I just fix
Re: [RFC][PATCH 0/2] dma-buf: add importer private data for reimporting
On Tue, Jun 04, 2013 at 07:42:22PM +0900, 김승우 wrote: > > > On 2013년 06월 01일 00:29, Daniel Vetter wrote: > > On Fri, May 31, 2013 at 07:22:24PM +0900, 김승우 wrote: > >> Hello Daniel, > >> > >> Thanks for your comment. > >> > >> On 2013년 05월 31일 18:14, Daniel Vetter wrote: > >>> On Fri, May 31, 2013 at 10:54 AM, Seung-Woo Kim > >>> wrote: > importer private data in dma-buf attachment can be used by importer to > reimport same dma-buf. > > Seung-Woo Kim (2): > dma-buf: add importer private data to attachment > drm/prime: find gem object from the reimported dma-buf > >>> > >>> Self-import should already work (at least with the latest refcount > >>> fixes merged). At least the tests to check both re-import on the same > >>> drm fd and on a different all work as expected now. > >> > >> Currently, prime works well for all case including self-importing, > >> importing, and reimporting as you describe. Just, importing dma-buf from > >> other driver twice with different drm_fd, each import create its own gem > >> object even two import is done for same buffer because prime_priv is in > >> struct drm_file. This means mapping to the device is done also twice. > >> IMHO, these duplicated creations and maps are not necessary if drm can > >> find previous import in different prime_priv. > > > > Well, that's imo a bug with the other driver. If it doesn't export > > something really simple (e.g. contiguous memory which doesn't require any > > mmio resources at all) it should have a cache of exported dma_buf fds so > > that it hands out the same dma_buf every time. > > Hm, all existing dma-buf exporter including i915 driver implements its > map_dma_buf callback as allocating scatter-gather table with pages in > its buffer and calling dma_map_sg() with the sgt. With different > drm_fds, importing one dma-buf *twice*, then importer calls > dma_buf_attach() and dma_buf_map_attachment() twice at least in drm > importer because re-importing case can only checked with prime_priv in > drm_file as I described. Well, but thanks to all the self-import and re-import checks, it's _impossible_ to import the same dma_buf twice without noticing (presuming both importer and exporter are drm devices). > > > > > Or it needs to be more clever in it's dma_buf_attachment_map functions and > > lookup up a pre-existing iommu mapping. > > > > But dealing with this in the importer is just broken. > > > >>> Second, the dma_buf_attachment is _definitely_ the wrong place to do > >>> this. If you need iommu mapping caching, that should happen at a lower > >>> level (i.e. in the map_attachment callback somewhere of the exporter, > >>> that's what the priv field in the attachment is for). Snatching away > >>> the attachement from some random other import is certainly not the way > >>> to go - attachements are _not_ refcounted! > >> > >> Yes, attachments do not have refcount, so importer should handle and drm > >> case in my patch, importer private data is gem object and it has, of > >> course, refcount. > >> > >> And at current, exporter can not classify map_dma_buf requests of same > >> importer to same buffer with different attachment because dma_buf_attach > >> always makes new attachments. To resolve this exporter should search all > >> different attachment from same importer of dma-buf and it seems more > >> complex than importer private data to me. > >> > >> If I misunderstood something, please let me know. > > > > Like I've said above, just fix this in the exporter. If an importer sees > > two different dma_bufs it can very well presume that it those two indeed > > point to different backing storage. > > Yes, my patch does not break this concept. I just fixed case importing > _one_ dma-buf twice with different drm_fds. See above, if you have two different struct file * for the same underlying buffer object something is wrong already. > > This will be even more important if we attach fences two dma_bufs. If your > > broken exporter creates multiple dma_bufs each one of them will have their > > own fences attached, leading to a complete disasters. Ok, strictly > > speaking if you keep the same reservation pointer for each dma_buf it'll > > work, but that's just a detail of how you solve this in the exporter. > > I can not understand about broken exporter you addressed. I don't mean > exporter makes dma-bufs from one backing storage. > While, my patch prevents not to create drm gem objects from one back > storage by importing one dma-buf with different drm-fds. Well, we also have code in drm prime for that case - if the same dma_buf object shows up multiple times, we'll only import it once. For the second import we'll return the already created drm_gem object from the first import, but with the refcount incremented. > I do not believe the fix of importer is the best way, but at this > moment, I have no idea how I can fix the exporter for this issue. I think if you have drm prime drivers both as impor
Re: [RFC][PATCH 0/2] dma-buf: add importer private data for reimporting
On 2013년 06월 01일 00:29, Daniel Vetter wrote: > On Fri, May 31, 2013 at 07:22:24PM +0900, 김승우 wrote: >> Hello Daniel, >> >> Thanks for your comment. >> >> On 2013년 05월 31일 18:14, Daniel Vetter wrote: >>> On Fri, May 31, 2013 at 10:54 AM, Seung-Woo Kim >>> wrote: importer private data in dma-buf attachment can be used by importer to reimport same dma-buf. Seung-Woo Kim (2): dma-buf: add importer private data to attachment drm/prime: find gem object from the reimported dma-buf >>> >>> Self-import should already work (at least with the latest refcount >>> fixes merged). At least the tests to check both re-import on the same >>> drm fd and on a different all work as expected now. >> >> Currently, prime works well for all case including self-importing, >> importing, and reimporting as you describe. Just, importing dma-buf from >> other driver twice with different drm_fd, each import create its own gem >> object even two import is done for same buffer because prime_priv is in >> struct drm_file. This means mapping to the device is done also twice. >> IMHO, these duplicated creations and maps are not necessary if drm can >> find previous import in different prime_priv. > > Well, that's imo a bug with the other driver. If it doesn't export > something really simple (e.g. contiguous memory which doesn't require any > mmio resources at all) it should have a cache of exported dma_buf fds so > that it hands out the same dma_buf every time. Hm, all existing dma-buf exporter including i915 driver implements its map_dma_buf callback as allocating scatter-gather table with pages in its buffer and calling dma_map_sg() with the sgt. With different drm_fds, importing one dma-buf *twice*, then importer calls dma_buf_attach() and dma_buf_map_attachment() twice at least in drm importer because re-importing case can only checked with prime_priv in drm_file as I described. > > Or it needs to be more clever in it's dma_buf_attachment_map functions and > lookup up a pre-existing iommu mapping. > > But dealing with this in the importer is just broken. > >>> Second, the dma_buf_attachment is _definitely_ the wrong place to do >>> this. If you need iommu mapping caching, that should happen at a lower >>> level (i.e. in the map_attachment callback somewhere of the exporter, >>> that's what the priv field in the attachment is for). Snatching away >>> the attachement from some random other import is certainly not the way >>> to go - attachements are _not_ refcounted! >> >> Yes, attachments do not have refcount, so importer should handle and drm >> case in my patch, importer private data is gem object and it has, of >> course, refcount. >> >> And at current, exporter can not classify map_dma_buf requests of same >> importer to same buffer with different attachment because dma_buf_attach >> always makes new attachments. To resolve this exporter should search all >> different attachment from same importer of dma-buf and it seems more >> complex than importer private data to me. >> >> If I misunderstood something, please let me know. > > Like I've said above, just fix this in the exporter. If an importer sees > two different dma_bufs it can very well presume that it those two indeed > point to different backing storage. Yes, my patch does not break this concept. I just fixed case importing _one_ dma-buf twice with different drm_fds. > > This will be even more important if we attach fences two dma_bufs. If your > broken exporter creates multiple dma_bufs each one of them will have their > own fences attached, leading to a complete disasters. Ok, strictly > speaking if you keep the same reservation pointer for each dma_buf it'll > work, but that's just a detail of how you solve this in the exporter. I can not understand about broken exporter you addressed. I don't mean exporter makes dma-bufs from one backing storage. While, my patch prevents not to create drm gem objects from one back storage by importing one dma-buf with different drm-fds. I do not believe the fix of importer is the best way, but at this moment, I have no idea how I can fix the exporter for this issue. Best Regards, - Seung-Woo Kim > > Cheers, Daniel > -- Seung-Woo Kim Samsung Software R&D Center -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC][PATCH 0/2] dma-buf: add importer private data for reimporting
On Fri, May 31, 2013 at 06:21:09PM +0200, Lucas Stach wrote: > Am Freitag, den 31.05.2013, 17:29 +0200 schrieb Daniel Vetter: > > On Fri, May 31, 2013 at 07:22:24PM +0900, 김승우 wrote: > > > Hello Daniel, > > > > > > Thanks for your comment. > > > > > > On 2013년 05월 31일 18:14, Daniel Vetter wrote: > > > > On Fri, May 31, 2013 at 10:54 AM, Seung-Woo Kim > > > > wrote: > > > >> importer private data in dma-buf attachment can be used by importer to > > > >> reimport same dma-buf. > > > >> > > > >> Seung-Woo Kim (2): > > > >> dma-buf: add importer private data to attachment > > > >> drm/prime: find gem object from the reimported dma-buf > > > > > > > > Self-import should already work (at least with the latest refcount > > > > fixes merged). At least the tests to check both re-import on the same > > > > drm fd and on a different all work as expected now. > > > > > > Currently, prime works well for all case including self-importing, > > > importing, and reimporting as you describe. Just, importing dma-buf from > > > other driver twice with different drm_fd, each import create its own gem > > > object even two import is done for same buffer because prime_priv is in > > > struct drm_file. This means mapping to the device is done also twice. > > > IMHO, these duplicated creations and maps are not necessary if drm can > > > find previous import in different prime_priv. > > > > Well, that's imo a bug with the other driver. If it doesn't export > > something really simple (e.g. contiguous memory which doesn't require any > > mmio resources at all) it should have a cache of exported dma_buf fds so > > that it hands out the same dma_buf every time. > > I agree with the reasoning here. > > Though it would be nice to have this "expected driver behavior" put down > somewhere in the documentation. Any volunteers? I'm not sure how much sense this makes. Imo the importer side is rather clearly spelled out, everything else is only now shaping up. And even with the clear interface spec we pretty much have no in-tree dma_buf user who doesn't cut corners somewhere for one or the other reason. As long the set of exporters is fairly limited we should be fine for now. -Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC][PATCH 0/2] dma-buf: add importer private data for reimporting
Am Freitag, den 31.05.2013, 17:29 +0200 schrieb Daniel Vetter: > On Fri, May 31, 2013 at 07:22:24PM +0900, 김승우 wrote: > > Hello Daniel, > > > > Thanks for your comment. > > > > On 2013년 05월 31일 18:14, Daniel Vetter wrote: > > > On Fri, May 31, 2013 at 10:54 AM, Seung-Woo Kim > > > wrote: > > >> importer private data in dma-buf attachment can be used by importer to > > >> reimport same dma-buf. > > >> > > >> Seung-Woo Kim (2): > > >> dma-buf: add importer private data to attachment > > >> drm/prime: find gem object from the reimported dma-buf > > > > > > Self-import should already work (at least with the latest refcount > > > fixes merged). At least the tests to check both re-import on the same > > > drm fd and on a different all work as expected now. > > > > Currently, prime works well for all case including self-importing, > > importing, and reimporting as you describe. Just, importing dma-buf from > > other driver twice with different drm_fd, each import create its own gem > > object even two import is done for same buffer because prime_priv is in > > struct drm_file. This means mapping to the device is done also twice. > > IMHO, these duplicated creations and maps are not necessary if drm can > > find previous import in different prime_priv. > > Well, that's imo a bug with the other driver. If it doesn't export > something really simple (e.g. contiguous memory which doesn't require any > mmio resources at all) it should have a cache of exported dma_buf fds so > that it hands out the same dma_buf every time. I agree with the reasoning here. Though it would be nice to have this "expected driver behavior" put down somewhere in the documentation. Any volunteers? Regards, Lucas -- Pengutronix e.K. | Lucas Stach | Industrial Linux Solutions | http://www.pengutronix.de/ | Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-5076 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917- | -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC][PATCH 0/2] dma-buf: add importer private data for reimporting
On Fri, May 31, 2013 at 07:22:24PM +0900, 김승우 wrote: > Hello Daniel, > > Thanks for your comment. > > On 2013년 05월 31일 18:14, Daniel Vetter wrote: > > On Fri, May 31, 2013 at 10:54 AM, Seung-Woo Kim > > wrote: > >> importer private data in dma-buf attachment can be used by importer to > >> reimport same dma-buf. > >> > >> Seung-Woo Kim (2): > >> dma-buf: add importer private data to attachment > >> drm/prime: find gem object from the reimported dma-buf > > > > Self-import should already work (at least with the latest refcount > > fixes merged). At least the tests to check both re-import on the same > > drm fd and on a different all work as expected now. > > Currently, prime works well for all case including self-importing, > importing, and reimporting as you describe. Just, importing dma-buf from > other driver twice with different drm_fd, each import create its own gem > object even two import is done for same buffer because prime_priv is in > struct drm_file. This means mapping to the device is done also twice. > IMHO, these duplicated creations and maps are not necessary if drm can > find previous import in different prime_priv. Well, that's imo a bug with the other driver. If it doesn't export something really simple (e.g. contiguous memory which doesn't require any mmio resources at all) it should have a cache of exported dma_buf fds so that it hands out the same dma_buf every time. Or it needs to be more clever in it's dma_buf_attachment_map functions and lookup up a pre-existing iommu mapping. But dealing with this in the importer is just broken. > > Second, the dma_buf_attachment is _definitely_ the wrong place to do > > this. If you need iommu mapping caching, that should happen at a lower > > level (i.e. in the map_attachment callback somewhere of the exporter, > > that's what the priv field in the attachment is for). Snatching away > > the attachement from some random other import is certainly not the way > > to go - attachements are _not_ refcounted! > > Yes, attachments do not have refcount, so importer should handle and drm > case in my patch, importer private data is gem object and it has, of > course, refcount. > > And at current, exporter can not classify map_dma_buf requests of same > importer to same buffer with different attachment because dma_buf_attach > always makes new attachments. To resolve this exporter should search all > different attachment from same importer of dma-buf and it seems more > complex than importer private data to me. > > If I misunderstood something, please let me know. Like I've said above, just fix this in the exporter. If an importer sees two different dma_bufs it can very well presume that it those two indeed point to different backing storage. This will be even more important if we attach fences two dma_bufs. If your broken exporter creates multiple dma_bufs each one of them will have their own fences attached, leading to a complete disasters. Ok, strictly speaking if you keep the same reservation pointer for each dma_buf it'll work, but that's just a detail of how you solve this in the exporter. Cheers, Daniel -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC][PATCH 0/2] dma-buf: add importer private data for reimporting
Hello Daniel, Thanks for your comment. On 2013년 05월 31일 18:14, Daniel Vetter wrote: > On Fri, May 31, 2013 at 10:54 AM, Seung-Woo Kim > wrote: >> importer private data in dma-buf attachment can be used by importer to >> reimport same dma-buf. >> >> Seung-Woo Kim (2): >> dma-buf: add importer private data to attachment >> drm/prime: find gem object from the reimported dma-buf > > Self-import should already work (at least with the latest refcount > fixes merged). At least the tests to check both re-import on the same > drm fd and on a different all work as expected now. Currently, prime works well for all case including self-importing, importing, and reimporting as you describe. Just, importing dma-buf from other driver twice with different drm_fd, each import create its own gem object even two import is done for same buffer because prime_priv is in struct drm_file. This means mapping to the device is done also twice. IMHO, these duplicated creations and maps are not necessary if drm can find previous import in different prime_priv. > > Second, the dma_buf_attachment is _definitely_ the wrong place to do > this. If you need iommu mapping caching, that should happen at a lower > level (i.e. in the map_attachment callback somewhere of the exporter, > that's what the priv field in the attachment is for). Snatching away > the attachement from some random other import is certainly not the way > to go - attachements are _not_ refcounted! Yes, attachments do not have refcount, so importer should handle and drm case in my patch, importer private data is gem object and it has, of course, refcount. And at current, exporter can not classify map_dma_buf requests of same importer to same buffer with different attachment because dma_buf_attach always makes new attachments. To resolve this exporter should search all different attachment from same importer of dma-buf and it seems more complex than importer private data to me. If I misunderstood something, please let me know. Best Regards, - Seung-Woo Kim > -Daniel > >> >> drivers/base/dma-buf.c | 31 >> >> drivers/gpu/drm/drm_prime.c| 19 >> drivers/gpu/drm/exynos/exynos_drm_dmabuf.c |1 + >> drivers/gpu/drm/i915/i915_gem_dmabuf.c |1 + >> drivers/gpu/drm/udl/udl_gem.c |1 + >> include/linux/dma-buf.h|4 +++ >> 6 files changed, 52 insertions(+), 5 deletions(-) >> >> -- >> 1.7.4.1 >> > > > > -- > Daniel Vetter > Software Engineer, Intel Corporation > +41 (0) 79 365 57 48 - http://blog.ffwll.ch > -- Seung-Woo Kim Samsung Software R&D Center -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC][PATCH 0/2] dma-buf: add importer private data for reimporting
On Fri, May 31, 2013 at 10:54 AM, Seung-Woo Kim wrote: > importer private data in dma-buf attachment can be used by importer to > reimport same dma-buf. > > Seung-Woo Kim (2): > dma-buf: add importer private data to attachment > drm/prime: find gem object from the reimported dma-buf Self-import should already work (at least with the latest refcount fixes merged). At least the tests to check both re-import on the same drm fd and on a different all work as expected now. Second, the dma_buf_attachment is _definitely_ the wrong place to do this. If you need iommu mapping caching, that should happen at a lower level (i.e. in the map_attachment callback somewhere of the exporter, that's what the priv field in the attachment is for). Snatching away the attachement from some random other import is certainly not the way to go - attachements are _not_ refcounted! -Daniel > > drivers/base/dma-buf.c | 31 > > drivers/gpu/drm/drm_prime.c| 19 > drivers/gpu/drm/exynos/exynos_drm_dmabuf.c |1 + > drivers/gpu/drm/i915/i915_gem_dmabuf.c |1 + > drivers/gpu/drm/udl/udl_gem.c |1 + > include/linux/dma-buf.h|4 +++ > 6 files changed, 52 insertions(+), 5 deletions(-) > > -- > 1.7.4.1 > -- Daniel Vetter Software Engineer, Intel Corporation +41 (0) 79 365 57 48 - http://blog.ffwll.ch -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
[RFC][PATCH 0/2] dma-buf: add importer private data for reimporting
importer private data in dma-buf attachment can be used by importer to reimport same dma-buf. Seung-Woo Kim (2): dma-buf: add importer private data to attachment drm/prime: find gem object from the reimported dma-buf drivers/base/dma-buf.c | 31 drivers/gpu/drm/drm_prime.c| 19 drivers/gpu/drm/exynos/exynos_drm_dmabuf.c |1 + drivers/gpu/drm/i915/i915_gem_dmabuf.c |1 + drivers/gpu/drm/udl/udl_gem.c |1 + include/linux/dma-buf.h|4 +++ 6 files changed, 52 insertions(+), 5 deletions(-) -- 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
