Re: [Spice-devel] [PATCH v2 1/1] video_video: Add the Virtio Video V4L2 driver
On Tue, Mar 17, 2020 at 6:10 PM Dmitry Sepp wrote: > > Hi Keiichi, > > On Dienstag, 17. März 2020 07:53:26 CET Keiichi Watanabe wrote: > > > > diff --git a/include/uapi/linux/virtio_video.h > > > > b/include/uapi/linux/virtio_video.h new file mode 100644 > > > > index ..0dd98a2237c6 > > > > --- /dev/null > > > > +++ b/include/uapi/linux/virtio_video.h > > > > @@ -0,0 +1,469 @@ > > > > +/* SPDX-License-Identifier: GPL-2.0+ */ > > > > > > I suspect it's not expected to use GPL licence without exceptions in a > > > UAPI header file: > > > https://www.kernel.org/doc/html/v5.4/process/license-rules.html > > > > > > If GPL is used here, only GPL user programs can include this header > > > file, can't they? > > > So, can we use BSD licence like other virtio headers (e.g. virtio_gpu.h)? > > > > > > Note that I found this program when running > > > /scripts/headers_install.sh. Though it suggested to add "WITH > > > Linux-syscall-note", it shouldn't be the case because this header > > > doesn't provide syscall interface. > > > > > > Best regards, > > > Keiichi > > > > > > > +/* > > > > + * Virtio Video Device > > > > + * > > > > + * This header is BSD licensed so anyone can use the definitions > > > > + * to implement compatible drivers/servers: > > > > + * > > > > Ah, this line says this header is BSD licensed. > > So, the SPDX-License-Identifier above should be simply wrong. > > > > According to some recent upstream discussion about virtio-snd, which was also > proposed by our engineers, it should be > /* SPDX-License-Identifier: BSD-3-Clause */ > Sounds good. Thanks for letting me know. Best regards, Keiichi > Best regards, > Dmitry. > > > Best regards, > > Keiichi > > ___ Spice-devel mailing list Spice-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/spice-devel
Re: [Spice-devel] [PATCH v2 1/1] video_video: Add the Virtio Video V4L2 driver
Hi Keiichi, On Dienstag, 17. März 2020 07:53:26 CET Keiichi Watanabe wrote: > > > diff --git a/include/uapi/linux/virtio_video.h > > > b/include/uapi/linux/virtio_video.h new file mode 100644 > > > index ..0dd98a2237c6 > > > --- /dev/null > > > +++ b/include/uapi/linux/virtio_video.h > > > @@ -0,0 +1,469 @@ > > > +/* SPDX-License-Identifier: GPL-2.0+ */ > > > > I suspect it's not expected to use GPL licence without exceptions in a > > UAPI header file: > > https://www.kernel.org/doc/html/v5.4/process/license-rules.html > > > > If GPL is used here, only GPL user programs can include this header > > file, can't they? > > So, can we use BSD licence like other virtio headers (e.g. virtio_gpu.h)? > > > > Note that I found this program when running > > /scripts/headers_install.sh. Though it suggested to add "WITH > > Linux-syscall-note", it shouldn't be the case because this header > > doesn't provide syscall interface. > > > > Best regards, > > Keiichi > > > > > +/* > > > + * Virtio Video Device > > > + * > > > + * This header is BSD licensed so anyone can use the definitions > > > + * to implement compatible drivers/servers: > > > + * > > Ah, this line says this header is BSD licensed. > So, the SPDX-License-Identifier above should be simply wrong. > According to some recent upstream discussion about virtio-snd, which was also proposed by our engineers, it should be /* SPDX-License-Identifier: BSD-3-Clause */ Best regards, Dmitry. > Best regards, > Keiichi ___ Spice-devel mailing list Spice-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/spice-devel
Re: [Spice-devel] [PATCH v2 1/1] video_video: Add the Virtio Video V4L2 driver
> > diff --git a/include/uapi/linux/virtio_video.h > > b/include/uapi/linux/virtio_video.h > > new file mode 100644 > > index ..0dd98a2237c6 > > --- /dev/null > > +++ b/include/uapi/linux/virtio_video.h > > @@ -0,0 +1,469 @@ > > +/* SPDX-License-Identifier: GPL-2.0+ */ > > I suspect it's not expected to use GPL licence without exceptions in a > UAPI header file: > https://www.kernel.org/doc/html/v5.4/process/license-rules.html > > If GPL is used here, only GPL user programs can include this header > file, can't they? > So, can we use BSD licence like other virtio headers (e.g. virtio_gpu.h)? > > Note that I found this program when running > /scripts/headers_install.sh. Though it suggested to add "WITH > Linux-syscall-note", it shouldn't be the case because this header > doesn't provide syscall interface. > > Best regards, > Keiichi > > > +/* > > + * Virtio Video Device > > + * > > + * This header is BSD licensed so anyone can use the definitions > > + * to implement compatible drivers/servers: > > + * Ah, this line says this header is BSD licensed. So, the SPDX-License-Identifier above should be simply wrong. Best regards, Keiichi ___ Spice-devel mailing list Spice-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/spice-devel
Re: [Spice-devel] [PATCH v2 1/1] video_video: Add the Virtio Video V4L2 driver
Hi Tomasz, On Freitag, 13. März 2020 12:11:51 CET Tomasz Figa wrote: > On Fri, Mar 13, 2020 at 11:27 AM Dmitry Sepp > > wrote: > > Hi Tomasz, > > > > On Freitag, 13. März 2020 11:05:35 CET Tomasz Figa wrote: > > > On Thu, Mar 12, 2020 at 12:48 PM Dmitry Sepp > > > > > > wrote: > > > > Hi Hans, > > > > > > > > One more thing: > > > > > GFP_DMA? That's unusual. I'd expect GFP_DMA32. All V4L2 drivers use > > > > > that. > > > > > > > > GFP_DMA32 had no effect for me on arm64. Probably I need to recheck. > > > > > > What's the reason to use any specific GFP flags at all? GFP_DMA(32) > > > memory in the guest would typically correspond to host pages without > > > any specific location guarantee. > > > > Typically, but not always, especially for non x86. Say, some platforms > > don't have IOMMUs for codec devices and those devices require physically > > contig low memory. We had to find a way to handle that. > > So basically your hypervisor guarantees that the guest pages inside > the GFP_DMA zone are contiguous and DMA-able on the host as well? > Given the Linux-specific aspect of GFP flags and differences in the > implementation across architectures, perhaps it would be a better idea > to use the DMA mask instead? That wouldn't currently affect vb2_dma_sg > allocations, but in that case the host decoder would have some IOMMU > anyway, right? > DMA mask has no effect for vb2_dma_sg, but GFP has. Unfortunately we need to support both of the two: low mem phys contig and low mem sg. So DMA mask cannot be an option. No, there are use-cases with obsolutely no iommus. Best regards, Dmitry. > > Best regards, > > Dmitry. > > > > > Best regards, > > > Tomasz > > > > > > > Best regards, > > > > Dmitry. > > > > > > > > On Donnerstag, 12. März 2020 11:18:26 CET Hans Verkuil wrote: > > > > > On 3/12/20 11:15 AM, Dmitry Sepp wrote: > > > > > > Hi Hans, > > > > > > > > > > > > Thank you for your great detailed review! > > > > > > > > > > > > I won't provide inline answers as your comments totally make > > > > > > sense. > > > > > > There > > > > > > is> > > > > > > > > > > > > only one thing I want to mention: > > > > > >>> + struct video_plane_format > > > > > >>> plane_format[VIRTIO_VIDEO_MAX_PLANES]; > > > > > >> > > > > > >> Why is this virtio specific? Any reason for not using > > > > > >> VIDEO_MAX_PLANES? > > > > > > > > > > > > I'd say this is because VIDEO_MAX_PLANES does not exist outside of > > > > > > the > > > > > > Linux OS, so for whatever other system we need a virtio specific > > > > > > definition. > > > > > > > > > > OK, good reason :-) > > > > > > > > > > It's probably a good thing to add a comment where > > > > > VIRTIO_VIDEO_MAX_PLANES is defined that explains this. > > > > > > > > > > Regards, > > > > > > > > > > Hans ___ Spice-devel mailing list Spice-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/spice-devel
Re: [Spice-devel] [PATCH v2 1/1] video_video: Add the Virtio Video V4L2 driver
On Fri, Mar 13, 2020 at 11:27 AM Dmitry Sepp wrote: > > Hi Tomasz, > > On Freitag, 13. März 2020 11:05:35 CET Tomasz Figa wrote: > > On Thu, Mar 12, 2020 at 12:48 PM Dmitry Sepp > > > > wrote: > > > Hi Hans, > > > > > > One more thing: > > > > GFP_DMA? That's unusual. I'd expect GFP_DMA32. All V4L2 drivers use > > > > that. > > > > > > GFP_DMA32 had no effect for me on arm64. Probably I need to recheck. > > > > What's the reason to use any specific GFP flags at all? GFP_DMA(32) > > memory in the guest would typically correspond to host pages without > > any specific location guarantee. > > > > Typically, but not always, especially for non x86. Say, some platforms don't > have IOMMUs for codec devices and those devices require physically contig low > memory. We had to find a way to handle that. So basically your hypervisor guarantees that the guest pages inside the GFP_DMA zone are contiguous and DMA-able on the host as well? Given the Linux-specific aspect of GFP flags and differences in the implementation across architectures, perhaps it would be a better idea to use the DMA mask instead? That wouldn't currently affect vb2_dma_sg allocations, but in that case the host decoder would have some IOMMU anyway, right? > > Best regards, > Dmitry. > > > Best regards, > > Tomasz > > > > > Best regards, > > > Dmitry. > > > > > > On Donnerstag, 12. März 2020 11:18:26 CET Hans Verkuil wrote: > > > > On 3/12/20 11:15 AM, Dmitry Sepp wrote: > > > > > Hi Hans, > > > > > > > > > > Thank you for your great detailed review! > > > > > > > > > > I won't provide inline answers as your comments totally make sense. > > > > > There > > > > > is> > > > > > > > > > > only one thing I want to mention: > > > > >>> + struct video_plane_format plane_format[VIRTIO_VIDEO_MAX_PLANES]; > > > > >> > > > > >> Why is this virtio specific? Any reason for not using > > > > >> VIDEO_MAX_PLANES? > > > > > > > > > > I'd say this is because VIDEO_MAX_PLANES does not exist outside of the > > > > > Linux OS, so for whatever other system we need a virtio specific > > > > > definition. > > > > > > > > OK, good reason :-) > > > > > > > > It's probably a good thing to add a comment where > > > > VIRTIO_VIDEO_MAX_PLANES is defined that explains this. > > > > > > > > Regards, > > > > > > > > Hans > > ___ Spice-devel mailing list Spice-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/spice-devel
Re: [Spice-devel] [PATCH v2 1/1] video_video: Add the Virtio Video V4L2 driver
On Thu, Mar 12, 2020 at 12:48 PM Dmitry Sepp wrote: > > Hi Hans, > > One more thing: > > > GFP_DMA? That's unusual. I'd expect GFP_DMA32. All V4L2 drivers use that. > > GFP_DMA32 had no effect for me on arm64. Probably I need to recheck. > What's the reason to use any specific GFP flags at all? GFP_DMA(32) memory in the guest would typically correspond to host pages without any specific location guarantee. Best regards, Tomasz > Best regards, > Dmitry. > > On Donnerstag, 12. März 2020 11:18:26 CET Hans Verkuil wrote: > > On 3/12/20 11:15 AM, Dmitry Sepp wrote: > > > Hi Hans, > > > > > > Thank you for your great detailed review! > > > > > > I won't provide inline answers as your comments totally make sense. There > > > is> > > > only one thing I want to mention: > > >>> + struct video_plane_format plane_format[VIRTIO_VIDEO_MAX_PLANES]; > > >> > > >> Why is this virtio specific? Any reason for not using VIDEO_MAX_PLANES? > > > > > > I'd say this is because VIDEO_MAX_PLANES does not exist outside of the > > > Linux OS, so for whatever other system we need a virtio specific > > > definition. > > OK, good reason :-) > > > > It's probably a good thing to add a comment where VIRTIO_VIDEO_MAX_PLANES is > > defined that explains this. > > > > Regards, > > > > Hans > > ___ Spice-devel mailing list Spice-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/spice-devel
Re: [Spice-devel] [PATCH v2 1/1] video_video: Add the Virtio Video V4L2 driver
Hi Tomasz, On Freitag, 13. März 2020 11:05:35 CET Tomasz Figa wrote: > On Thu, Mar 12, 2020 at 12:48 PM Dmitry Sepp > > wrote: > > Hi Hans, > > > > One more thing: > > > GFP_DMA? That's unusual. I'd expect GFP_DMA32. All V4L2 drivers use > > > that. > > > > GFP_DMA32 had no effect for me on arm64. Probably I need to recheck. > > What's the reason to use any specific GFP flags at all? GFP_DMA(32) > memory in the guest would typically correspond to host pages without > any specific location guarantee. > Typically, but not always, especially for non x86. Say, some platforms don't have IOMMUs for codec devices and those devices require physically contig low memory. We had to find a way to handle that. Best regards, Dmitry. > Best regards, > Tomasz > > > Best regards, > > Dmitry. > > > > On Donnerstag, 12. März 2020 11:18:26 CET Hans Verkuil wrote: > > > On 3/12/20 11:15 AM, Dmitry Sepp wrote: > > > > Hi Hans, > > > > > > > > Thank you for your great detailed review! > > > > > > > > I won't provide inline answers as your comments totally make sense. > > > > There > > > > is> > > > > > > > > only one thing I want to mention: > > > >>> + struct video_plane_format plane_format[VIRTIO_VIDEO_MAX_PLANES]; > > > >> > > > >> Why is this virtio specific? Any reason for not using > > > >> VIDEO_MAX_PLANES? > > > > > > > > I'd say this is because VIDEO_MAX_PLANES does not exist outside of the > > > > Linux OS, so for whatever other system we need a virtio specific > > > > definition. > > > > > > OK, good reason :-) > > > > > > It's probably a good thing to add a comment where > > > VIRTIO_VIDEO_MAX_PLANES is defined that explains this. > > > > > > Regards, > > > > > > Hans ___ Spice-devel mailing list Spice-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/spice-devel
Re: [Spice-devel] [PATCH v2 1/1] video_video: Add the Virtio Video V4L2 driver
Hi Hans, One more thing: > GFP_DMA? That's unusual. I'd expect GFP_DMA32. All V4L2 drivers use that. GFP_DMA32 had no effect for me on arm64. Probably I need to recheck. Best regards, Dmitry. On Donnerstag, 12. März 2020 11:18:26 CET Hans Verkuil wrote: > On 3/12/20 11:15 AM, Dmitry Sepp wrote: > > Hi Hans, > > > > Thank you for your great detailed review! > > > > I won't provide inline answers as your comments totally make sense. There > > is> > > only one thing I want to mention: > >>> + struct video_plane_format plane_format[VIRTIO_VIDEO_MAX_PLANES]; > >> > >> Why is this virtio specific? Any reason for not using VIDEO_MAX_PLANES? > > > > I'd say this is because VIDEO_MAX_PLANES does not exist outside of the > > Linux OS, so for whatever other system we need a virtio specific > > definition. > OK, good reason :-) > > It's probably a good thing to add a comment where VIRTIO_VIDEO_MAX_PLANES is > defined that explains this. > > Regards, > > Hans ___ Spice-devel mailing list Spice-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/spice-devel
Re: [Spice-devel] [PATCH v2 1/1] video_video: Add the Virtio Video V4L2 driver
On 3/12/20 11:15 AM, Dmitry Sepp wrote: > Hi Hans, > > Thank you for your great detailed review! > > I won't provide inline answers as your comments totally make sense. There is > only one thing I want to mention: > >>> + struct video_plane_format plane_format[VIRTIO_VIDEO_MAX_PLANES]; >> >> Why is this virtio specific? Any reason for not using VIDEO_MAX_PLANES? > > I'd say this is because VIDEO_MAX_PLANES does not exist outside of the Linux > OS, so for whatever other system we need a virtio specific definition. OK, good reason :-) It's probably a good thing to add a comment where VIRTIO_VIDEO_MAX_PLANES is defined that explains this. Regards, Hans ___ Spice-devel mailing list Spice-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/spice-devel
