| Message ID | ZS+392ZzVIoEyv8n@fedora (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] ALSA: virtio: use copy and fill_silence callbacks | expand |
Hello Takashi, On Thu, Oct 19, 2023 at 09:48:03AM +0200, Takashi Iwai wrote: > On Thu, 19 Oct 2023 03:20:19 +0200, > Anton Yakovlev wrote: > > > > Hi Takashi, > > > > On 19.10.2023 03:07, Takashi Iwai wrote: > > > On Wed, 18 Oct 2023 12:48:23 +0200, > > > Matias Ezequiel Vara Larsen wrote: > > >> > > >> This commit replaces the mmap mechanism with the copy() and > > >> fill_silence() callbacks for both capturing and playback for the > > >> virtio-sound driver. This change is required to prevent the updating of > > >> the content of a buffer that is already in the available ring. > > >> > > >> The current mechanism splits a dma buffer into descriptors that are > > >> exposed to the device. This dma buffer is shared with the user > > >> application. When the device consumes a buffer, the driver moves the > > >> request from the used ring to available ring. > > >> > > >> The driver exposes the buffer to the device without knowing if the > > >> content has been updated from the user. The section 2.8.21.1 of the > > >> virtio spec states that: "The device MAY access the descriptor chains > > >> the driver created and the memory they refer to immediately". If the > > >> device picks up buffers from the available ring just after it is > > >> notified, it happens that the content may be old. > > >> > > >> By providing the copy() callback, the driver first updates the content > > >> of the buffer, and then, exposes the buffer to the device by enqueuing > > >> it in the available ring. Thus, device always picks up a buffer that is > > >> updated. During copy(), the number of requests enqueued depends on the > > >> "pos" and "bytes" arguments. The length of each request is period_size > > >> bytes. > > >> > > >> For capturing, the driver starts by exposing all the available buffers > > >> to device. After device updates the content of a buffer, it enqueues it > > >> in the used ring. It is only after the copy() for capturing is issued > > >> that the driver re-enqueues the buffer in the available ring. > > >> > > >> Co-developed-by: Anton Yakovlev <anton.yakovlev@opensynergy.com> > > >> Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> > > >> --- > > >> Changelog: > > >> v1 -> v2: > > >> * Use snd_pcm_set_managed_buffer_all()for buffer allocation/freeing. > > >> * Make virtsnd_pcm_msg_send() generic by specifying the offset and size > > >> for the modified part of the buffer; this way no assumptions need to > > >> be made. > > >> * Disable SNDRV_PCM_INFO_NO_REWINDS since now only sequential > > >> reading/writing of frames is supported. > > >> * Correct comment at virtsnd_pcm_msg_send(). > > >> * v1 patch at: > > >> https://ddec1-0-en-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=https%3a%2f%2flore.kernel.org%2flkml%2f20231016151000.GE119987%40fedora%2ft%2f&umid=2f305b77-83e7-47b6-a461-a8ca67d0bfe2&auth=53c7c7de28b92dfd96e93d9dd61a23e634d2fbec-2d5775265e7e1741ae8eb783a3cb78ed553093c1 > > >> > > >> sound/virtio/virtio_pcm.c | 7 ++- > > >> sound/virtio/virtio_pcm.h | 9 ++-- > > >> sound/virtio/virtio_pcm_msg.c | 93 ++++++++++++++++++++++------------- > > >> sound/virtio/virtio_pcm_ops.c | 81 +++++++++++++++++++++++++----- > > >> 4 files changed, 137 insertions(+), 53 deletions(-) > > > > > > Most of the code changes look good, but I wonder: > > > > > >> > > >> diff --git a/sound/virtio/virtio_pcm.c b/sound/virtio/virtio_pcm.c > > >> index c10d91fff2fb..66d67eef1bcc 100644 > > >> --- a/sound/virtio/virtio_pcm.c > > >> +++ b/sound/virtio/virtio_pcm.c > > >> @@ -104,12 +104,11 @@ static int virtsnd_pcm_build_hw(struct virtio_pcm_substream *vss, > > >> * only message-based transport. > > >> */ > > >> vss->hw.info = > > >> - SNDRV_PCM_INFO_MMAP | > > >> - SNDRV_PCM_INFO_MMAP_VALID | > > > > > > Do we need the removal of those MMAP features inevitably? > > > Usually mmap can still work even if the driver implements the copy > > > ops. Those aren't always mutual exclusive. > > > > The driver uses a message queue to communicate with the device. Thus, > > the audio buffer is sliced into several I/O requests (= number of > > periods) of the same size (= period size). > > > > Before this, all such requests were enqueued when the substream started, > > and immediately re-enqueued once the request is completed. This approach > > made it possible to add mmap support. But for mmap there are no explicit > > notifications from the application how many frames were written or read. > > Thus, it was assumed that the virtual device should read/write frames to > > requests based on timings. And there are some problems here: > > > > 1. This was found to violate the virtio specification: if a request is > > already in the queue, the device can safely read/write there at any > > time. > > 2. It looks like this breaks the use case with swiotlb. Personally I'm > > not sure how the application handles DMA ownership in the case of > > mmaped buffer. > > > > To correctly implement mmap support, instead of transferring data via a > > message queue, the driver and device must have a shared memory region. > > We can add mmap in the future when we expand the functionality of the > > device to support such shared memory. > > Ah, then this implementation might be an overkill. You're still using > the (intermediate) vmalloc buffer allocated via PCM managed mode, and > the actual data is copied from/to there. So it doesn't conflict with > the mmap operation at all. > > I guess that the problem you're trying to solve (the immediate data > transfer to the queue) can be implemented rather via PCM ack callback > instead. ALSA PCM core notifies the possible data transfer via PCM > ack callback right after each change of appl_ptr or hw_ptr, including > each read/write op or mmap commit. Then the driver can check the > change of appl_ptr (or hw_ptr for capture), fetch the newly available > data, and queue it immediately. > > Usually together with the use of ack callback, the driver sets > SNDRV_PCM_INFO_SYNC_APPLPTR flag. This prevents the mmap of the PCM > control record (not the audio data) and enforces the use of > SNDRV_PCM_IOCTL_SYNC_PTR ioctl instead (so that the driver always gets > the ack callback). > > Thanks for your comments. If I understand correctly, we have two options: 1. Use copy/fill_silence callbacks and use my own buffers thus disabling mmap. 2. Use mmap and the ack callback to track when appl_ptr changes thus moving the content to the queues after it has been updated. Am I right? Thanks, Matias. > thanks, > > Takashi > > > > > > > > Best regards, > > > > > > > > > > > thanks, > > > > > > Takashi > > > > -- > > Anton Yakovlev > > Senior Software Engineer > > > > OpenSynergy GmbH > > Rotherstr. 20, 10245 Berlin > > >
On Fri, 20 Oct 2023 11:45:39 +0200, Matias Ezequiel Vara Larsen wrote: > > Hello Takashi, > > On Thu, Oct 19, 2023 at 09:48:03AM +0200, Takashi Iwai wrote: > > On Thu, 19 Oct 2023 03:20:19 +0200, > > Anton Yakovlev wrote: > > > > > > Hi Takashi, > > > > > > On 19.10.2023 03:07, Takashi Iwai wrote: > > > > On Wed, 18 Oct 2023 12:48:23 +0200, > > > > Matias Ezequiel Vara Larsen wrote: > > > >> > > > >> This commit replaces the mmap mechanism with the copy() and > > > >> fill_silence() callbacks for both capturing and playback for the > > > >> virtio-sound driver. This change is required to prevent the updating of > > > >> the content of a buffer that is already in the available ring. > > > >> > > > >> The current mechanism splits a dma buffer into descriptors that are > > > >> exposed to the device. This dma buffer is shared with the user > > > >> application. When the device consumes a buffer, the driver moves the > > > >> request from the used ring to available ring. > > > >> > > > >> The driver exposes the buffer to the device without knowing if the > > > >> content has been updated from the user. The section 2.8.21.1 of the > > > >> virtio spec states that: "The device MAY access the descriptor chains > > > >> the driver created and the memory they refer to immediately". If the > > > >> device picks up buffers from the available ring just after it is > > > >> notified, it happens that the content may be old. > > > >> > > > >> By providing the copy() callback, the driver first updates the content > > > >> of the buffer, and then, exposes the buffer to the device by enqueuing > > > >> it in the available ring. Thus, device always picks up a buffer that is > > > >> updated. During copy(), the number of requests enqueued depends on the > > > >> "pos" and "bytes" arguments. The length of each request is period_size > > > >> bytes. > > > >> > > > >> For capturing, the driver starts by exposing all the available buffers > > > >> to device. After device updates the content of a buffer, it enqueues it > > > >> in the used ring. It is only after the copy() for capturing is issued > > > >> that the driver re-enqueues the buffer in the available ring. > > > >> > > > >> Co-developed-by: Anton Yakovlev <anton.yakovlev@opensynergy.com> > > > >> Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> > > > >> --- > > > >> Changelog: > > > >> v1 -> v2: > > > >> * Use snd_pcm_set_managed_buffer_all()for buffer allocation/freeing. > > > >> * Make virtsnd_pcm_msg_send() generic by specifying the offset and size > > > >> for the modified part of the buffer; this way no assumptions need to > > > >> be made. > > > >> * Disable SNDRV_PCM_INFO_NO_REWINDS since now only sequential > > > >> reading/writing of frames is supported. > > > >> * Correct comment at virtsnd_pcm_msg_send(). > > > >> * v1 patch at: > > > >> https://ddec1-0-en-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=https%3a%2f%2flore.kernel.org%2flkml%2f20231016151000.GE119987%40fedora%2ft%2f&umid=2f305b77-83e7-47b6-a461-a8ca67d0bfe2&auth=53c7c7de28b92dfd96e93d9dd61a23e634d2fbec-2d5775265e7e1741ae8eb783a3cb78ed553093c1 > > > >> > > > >> sound/virtio/virtio_pcm.c | 7 ++- > > > >> sound/virtio/virtio_pcm.h | 9 ++-- > > > >> sound/virtio/virtio_pcm_msg.c | 93 ++++++++++++++++++++++------------- > > > >> sound/virtio/virtio_pcm_ops.c | 81 +++++++++++++++++++++++++----- > > > >> 4 files changed, 137 insertions(+), 53 deletions(-) > > > > > > > > Most of the code changes look good, but I wonder: > > > > > > > >> > > > >> diff --git a/sound/virtio/virtio_pcm.c b/sound/virtio/virtio_pcm.c > > > >> index c10d91fff2fb..66d67eef1bcc 100644 > > > >> --- a/sound/virtio/virtio_pcm.c > > > >> +++ b/sound/virtio/virtio_pcm.c > > > >> @@ -104,12 +104,11 @@ static int virtsnd_pcm_build_hw(struct virtio_pcm_substream *vss, > > > >> * only message-based transport. > > > >> */ > > > >> vss->hw.info = > > > >> - SNDRV_PCM_INFO_MMAP | > > > >> - SNDRV_PCM_INFO_MMAP_VALID | > > > > > > > > Do we need the removal of those MMAP features inevitably? > > > > Usually mmap can still work even if the driver implements the copy > > > > ops. Those aren't always mutual exclusive. > > > > > > The driver uses a message queue to communicate with the device. Thus, > > > the audio buffer is sliced into several I/O requests (= number of > > > periods) of the same size (= period size). > > > > > > Before this, all such requests were enqueued when the substream started, > > > and immediately re-enqueued once the request is completed. This approach > > > made it possible to add mmap support. But for mmap there are no explicit > > > notifications from the application how many frames were written or read. > > > Thus, it was assumed that the virtual device should read/write frames to > > > requests based on timings. And there are some problems here: > > > > > > 1. This was found to violate the virtio specification: if a request is > > > already in the queue, the device can safely read/write there at any > > > time. > > > 2. It looks like this breaks the use case with swiotlb. Personally I'm > > > not sure how the application handles DMA ownership in the case of > > > mmaped buffer. > > > > > > To correctly implement mmap support, instead of transferring data via a > > > message queue, the driver and device must have a shared memory region. > > > We can add mmap in the future when we expand the functionality of the > > > device to support such shared memory. > > > > Ah, then this implementation might be an overkill. You're still using > > the (intermediate) vmalloc buffer allocated via PCM managed mode, and > > the actual data is copied from/to there. So it doesn't conflict with > > the mmap operation at all. > > > > I guess that the problem you're trying to solve (the immediate data > > transfer to the queue) can be implemented rather via PCM ack callback > > instead. ALSA PCM core notifies the possible data transfer via PCM > > ack callback right after each change of appl_ptr or hw_ptr, including > > each read/write op or mmap commit. Then the driver can check the > > change of appl_ptr (or hw_ptr for capture), fetch the newly available > > data, and queue it immediately. > > > > Usually together with the use of ack callback, the driver sets > > SNDRV_PCM_INFO_SYNC_APPLPTR flag. This prevents the mmap of the PCM > > control record (not the audio data) and enforces the use of > > SNDRV_PCM_IOCTL_SYNC_PTR ioctl instead (so that the driver always gets > > the ack callback). > > > > > > Thanks for your comments. If I understand correctly, we have two > options: > 1. Use copy/fill_silence callbacks and use my own buffers thus disabling > mmap. > 2. Use mmap and the ack callback to track when appl_ptr changes thus > moving the content to the queues after it has been updated. > > Am I right? Not really. The ack callback is always effective no matter whether the stream is transferred via mmap or read/write. So, when you implement a la packet transfer via ack callback, it works for both mmap and read/write. It's used typically for drivers doing a packet-based transfer, e.g. FireWire drivers or USB-audio. OTOH, if you'd like to drop the intermediate ring buffer (enabled by snd_pcm_set_managed_buffer_all() and allocated/freed automatically at hw_params/hw_free in PCM core), you can implement PCM copy and fill_ops methods. But in this case, you can't copy to runtime->dma_area like your patch; you may need a temporary buffer of your own, or handle directly the user pointer. And, even with copy/fill_ops implementations, mmap itself isn't prohibited when the driver provides its own mmap call. This can be seen, for example, when a driver uses the iomem region as the data ring buffer. HTH, Takashi > Thanks, Matias. > > > thanks, > > > > Takashi > > > > > > > > > > > > > Best regards, > > > > > > > > > > > > > > > thanks, > > > > > > > > Takashi > > > > > > -- > > > Anton Yakovlev > > > Senior Software Engineer > > > > > > OpenSynergy GmbH > > > Rotherstr. 20, 10245 Berlin > > > > > >
Hi Takashi, On 19.10.2023 16:48, Takashi Iwai wrote: > On Thu, 19 Oct 2023 03:20:19 +0200, > Anton Yakovlev wrote: >> >> Hi Takashi, >> >> On 19.10.2023 03:07, Takashi Iwai wrote: >>> On Wed, 18 Oct 2023 12:48:23 +0200, >>> Matias Ezequiel Vara Larsen wrote: >>>> >>>> This commit replaces the mmap mechanism with the copy() and >>>> fill_silence() callbacks for both capturing and playback for the >>>> virtio-sound driver. This change is required to prevent the updating of >>>> the content of a buffer that is already in the available ring. >>>> >>>> The current mechanism splits a dma buffer into descriptors that are >>>> exposed to the device. This dma buffer is shared with the user >>>> application. When the device consumes a buffer, the driver moves the >>>> request from the used ring to available ring. >>>> >>>> The driver exposes the buffer to the device without knowing if the >>>> content has been updated from the user. The section 2.8.21.1 of the >>>> virtio spec states that: "The device MAY access the descriptor chains >>>> the driver created and the memory they refer to immediately". If the >>>> device picks up buffers from the available ring just after it is >>>> notified, it happens that the content may be old. >>>> >>>> By providing the copy() callback, the driver first updates the content >>>> of the buffer, and then, exposes the buffer to the device by enqueuing >>>> it in the available ring. Thus, device always picks up a buffer that is >>>> updated. During copy(), the number of requests enqueued depends on the >>>> "pos" and "bytes" arguments. The length of each request is period_size >>>> bytes. >>>> >>>> For capturing, the driver starts by exposing all the available buffers >>>> to device. After device updates the content of a buffer, it enqueues it >>>> in the used ring. It is only after the copy() for capturing is issued >>>> that the driver re-enqueues the buffer in the available ring. >>>> >>>> Co-developed-by: Anton Yakovlev <anton.yakovlev@opensynergy.com> >>>> Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> >>>> --- >>>> Changelog: >>>> v1 -> v2: >>>> * Use snd_pcm_set_managed_buffer_all()for buffer allocation/freeing. >>>> * Make virtsnd_pcm_msg_send() generic by specifying the offset and size >>>> for the modified part of the buffer; this way no assumptions need to >>>> be made. >>>> * Disable SNDRV_PCM_INFO_NO_REWINDS since now only sequential >>>> reading/writing of frames is supported. >>>> * Correct comment at virtsnd_pcm_msg_send(). >>>> * v1 patch at: >>>> https://ddec1-0-en-ctp.trendmicro.com:443/wis/clicktime/v1/query?url=https%3a%2f%2flore.kernel.org%2flkml%2f20231016151000.GE119987%40fedora%2ft%2f&umid=323acbff-2d10-45a8-bbe1-78fc8583abec&auth=53c7c7de28b92dfd96e93d9dd61a23e634d2fbec-6526c5e588ae6e2c247d0c967e0504e4fc7f307a >>>> >>>> sound/virtio/virtio_pcm.c | 7 ++- >>>> sound/virtio/virtio_pcm.h | 9 ++-- >>>> sound/virtio/virtio_pcm_msg.c | 93 ++++++++++++++++++++++------------- >>>> sound/virtio/virtio_pcm_ops.c | 81 +++++++++++++++++++++++++----- >>>> 4 files changed, 137 insertions(+), 53 deletions(-) >>> >>> Most of the code changes look good, but I wonder: >>> >>>> >>>> diff --git a/sound/virtio/virtio_pcm.c b/sound/virtio/virtio_pcm.c >>>> index c10d91fff2fb..66d67eef1bcc 100644 >>>> --- a/sound/virtio/virtio_pcm.c >>>> +++ b/sound/virtio/virtio_pcm.c >>>> @@ -104,12 +104,11 @@ static int virtsnd_pcm_build_hw(struct virtio_pcm_substream *vss, >>>> * only message-based transport. >>>> */ >>>> vss->hw.info = >>>> - SNDRV_PCM_INFO_MMAP | >>>> - SNDRV_PCM_INFO_MMAP_VALID | >>> >>> Do we need the removal of those MMAP features inevitably? >>> Usually mmap can still work even if the driver implements the copy >>> ops. Those aren't always mutual exclusive. >> >> The driver uses a message queue to communicate with the device. Thus, >> the audio buffer is sliced into several I/O requests (= number of >> periods) of the same size (= period size). >> >> Before this, all such requests were enqueued when the substream started, >> and immediately re-enqueued once the request is completed. This approach >> made it possible to add mmap support. But for mmap there are no explicit >> notifications from the application how many frames were written or read. >> Thus, it was assumed that the virtual device should read/write frames to >> requests based on timings. And there are some problems here: >> >> 1. This was found to violate the virtio specification: if a request is >> already in the queue, the device can safely read/write there at any >> time. >> 2. It looks like this breaks the use case with swiotlb. Personally I'm >> not sure how the application handles DMA ownership in the case of >> mmaped buffer. >> >> To correctly implement mmap support, instead of transferring data via a >> message queue, the driver and device must have a shared memory region. >> We can add mmap in the future when we expand the functionality of the >> device to support such shared memory. > > Ah, then this implementation might be an overkill. You're still using > the (intermediate) vmalloc buffer allocated via PCM managed mode, and > the actual data is copied from/to there. So it doesn't conflict with > the mmap operation at all. > > I guess that the problem you're trying to solve (the immediate data > transfer to the queue) can be implemented rather via PCM ack callback > instead. ALSA PCM core notifies the possible data transfer via PCM > ack callback right after each change of appl_ptr or hw_ptr, including > each read/write op or mmap commit. Then the driver can check the > change of appl_ptr (or hw_ptr for capture), fetch the newly available > data, and queue it immediately. > > Usually together with the use of ack callback, the driver sets > SNDRV_PCM_INFO_SYNC_APPLPTR flag. This prevents the mmap of the PCM > control record (not the audio data) and enforces the use of > SNDRV_PCM_IOCTL_SYNC_PTR ioctl instead (so that the driver always gets > the ack callback). Thanks for pointing out this possibility! I'm wondering if TinyALSA works correctly with this flag. Best regards, > > > thanks, > > Takashi > > >> >> >> Best regards, >> >>> >>> >>> thanks, >>> >>> Takashi >> >> -- >> Anton Yakovlev >> Senior Software Engineer >> >> OpenSynergy GmbH >> Rotherstr. 20, 10245 Berlin
diff --git a/sound/virtio/virtio_pcm.c b/sound/virtio/virtio_pcm.c index c10d91fff2fb..66d67eef1bcc 100644 --- a/sound/virtio/virtio_pcm.c +++ b/sound/virtio/virtio_pcm.c @@ -104,12 +104,11 @@ static int virtsnd_pcm_build_hw(struct virtio_pcm_substream *vss, * only message-based transport. */ vss->hw.info = - SNDRV_PCM_INFO_MMAP | - SNDRV_PCM_INFO_MMAP_VALID | SNDRV_PCM_INFO_BATCH | SNDRV_PCM_INFO_BLOCK_TRANSFER | SNDRV_PCM_INFO_INTERLEAVED | - SNDRV_PCM_INFO_PAUSE; + SNDRV_PCM_INFO_PAUSE | + SNDRV_PCM_INFO_NO_REWINDS; if (!info->channels_min || info->channels_min > info->channels_max) { dev_err(&vdev->dev, @@ -471,7 +470,7 @@ int virtsnd_pcm_build_devs(struct virtio_snd *snd) for (kss = ks->substream; kss; kss = kss->next) vs->substreams[kss->number]->substream = kss; - snd_pcm_set_ops(vpcm->pcm, i, &virtsnd_pcm_ops); + snd_pcm_set_ops(vpcm->pcm, i, &virtsnd_pcm_ops[i]); } snd_pcm_set_managed_buffer_all(vpcm->pcm, diff --git a/sound/virtio/virtio_pcm.h b/sound/virtio/virtio_pcm.h index 062eb8e8f2cf..8b42928a8e01 100644 --- a/sound/virtio/virtio_pcm.h +++ b/sound/virtio/virtio_pcm.h @@ -57,7 +57,6 @@ struct virtio_pcm_substream { bool suspended; struct virtio_pcm_msg **msgs; unsigned int nmsgs; - int msg_last_enqueued; unsigned int msg_count; wait_queue_head_t msg_empty; }; @@ -90,7 +89,7 @@ struct virtio_pcm { struct virtio_pcm_stream streams[SNDRV_PCM_STREAM_LAST + 1]; }; -extern const struct snd_pcm_ops virtsnd_pcm_ops; +extern const struct snd_pcm_ops virtsnd_pcm_ops[]; int virtsnd_pcm_validate(struct virtio_device *vdev); @@ -117,7 +116,11 @@ int virtsnd_pcm_msg_alloc(struct virtio_pcm_substream *vss, void virtsnd_pcm_msg_free(struct virtio_pcm_substream *vss); -int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss); +int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss, unsigned long offset, + unsigned long bytes); + +int virtsnd_pcm_msg_send_locked(struct virtio_pcm_substream *vss, + unsigned long offset, unsigned long bytes); unsigned int virtsnd_pcm_msg_pending_num(struct virtio_pcm_substream *vss); diff --git a/sound/virtio/virtio_pcm_msg.c b/sound/virtio/virtio_pcm_msg.c index aca2dc1989ba..c3d471088d9e 100644 --- a/sound/virtio/virtio_pcm_msg.c +++ b/sound/virtio/virtio_pcm_msg.c @@ -155,7 +155,6 @@ int virtsnd_pcm_msg_alloc(struct virtio_pcm_substream *vss, sizeof(msg->xfer)); sg_init_one(&msg->sgs[PCM_MSG_SG_STATUS], &msg->status, sizeof(msg->status)); - msg->length = period_bytes; virtsnd_pcm_sg_from(&msg->sgs[PCM_MSG_SG_DATA], sg_num, data, period_bytes); @@ -189,58 +188,70 @@ void virtsnd_pcm_msg_free(struct virtio_pcm_substream *vss) * * All messages are organized in an ordered circular list. Each time the * function is called, all currently non-enqueued messages are added to the - * virtqueue. For this, the function keeps track of two values: - * - * msg_last_enqueued = index of the last enqueued message, - * msg_count = # of pending messages in the virtqueue. + * virtqueue. For this, the function uses offset and bytes to calculate the + * messages that need to be added. * * Context: Any context. Expects the tx/rx queue and the VirtIO substream * spinlocks to be held by caller. * Return: 0 on success, -errno on failure. */ -int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss) +int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss, unsigned long offset, + unsigned long bytes) { - struct snd_pcm_runtime *runtime = vss->substream->runtime; struct virtio_snd *snd = vss->snd; struct virtio_device *vdev = snd->vdev; struct virtqueue *vqueue = virtsnd_pcm_queue(vss)->vqueue; - int i; - int n; + unsigned long period_bytes = snd_pcm_lib_period_bytes(vss->substream); + unsigned long start, end, i; + unsigned int msg_count = vss->msg_count; bool notify = false; + int rc; - i = (vss->msg_last_enqueued + 1) % runtime->periods; - n = runtime->periods - vss->msg_count; + start = offset / period_bytes; + end = (offset + bytes - 1) / period_bytes; - for (; n; --n, i = (i + 1) % runtime->periods) { + for (i = start; i <= end; i++) { struct virtio_pcm_msg *msg = vss->msgs[i]; struct scatterlist *psgs[] = { &msg->sgs[PCM_MSG_SG_XFER], &msg->sgs[PCM_MSG_SG_DATA], &msg->sgs[PCM_MSG_SG_STATUS] }; - int rc; - - msg->xfer.stream_id = cpu_to_le32(vss->sid); - memset(&msg->status, 0, sizeof(msg->status)); - - if (vss->direction == SNDRV_PCM_STREAM_PLAYBACK) - rc = virtqueue_add_sgs(vqueue, psgs, 2, 1, msg, - GFP_ATOMIC); - else - rc = virtqueue_add_sgs(vqueue, psgs, 1, 2, msg, - GFP_ATOMIC); - - if (rc) { - dev_err(&vdev->dev, - "SID %u: failed to send I/O message\n", - vss->sid); - return rc; + unsigned long n; + + n = period_bytes - (offset % period_bytes); + if (n > bytes) + n = bytes; + + msg->length += n; + if (msg->length == period_bytes) { + msg->xfer.stream_id = cpu_to_le32(vss->sid); + memset(&msg->status, 0, sizeof(msg->status)); + + if (vss->direction == SNDRV_PCM_STREAM_PLAYBACK) + rc = virtqueue_add_sgs(vqueue, psgs, 2, 1, msg, + GFP_ATOMIC); + else + rc = virtqueue_add_sgs(vqueue, psgs, 1, 2, msg, + GFP_ATOMIC); + + if (rc) { + dev_err(&vdev->dev, + "SID %u: failed to send I/O message\n", + vss->sid); + return rc; + } + + vss->msg_count++; } - vss->msg_last_enqueued = i; - vss->msg_count++; + offset = 0; + bytes -= n; } + if (msg_count == vss->msg_count) + return 0; + if (!(vss->features & (1U << VIRTIO_SND_PCM_F_MSG_POLLING))) notify = virtqueue_kick_prepare(vqueue); @@ -250,6 +261,22 @@ int virtsnd_pcm_msg_send(struct virtio_pcm_substream *vss) return 0; } +int virtsnd_pcm_msg_send_locked(struct virtio_pcm_substream *vss, + unsigned long offset, unsigned long bytes) +{ + struct virtio_snd_queue *queue = virtsnd_pcm_queue(vss); + unsigned long flags; + int rc; + + spin_lock_irqsave(&queue->lock, flags); + spin_lock(&vss->lock); + rc = virtsnd_pcm_msg_send(vss, offset, bytes); + spin_unlock(&vss->lock); + spin_unlock_irqrestore(&queue->lock, flags); + + return rc; +} + /** * virtsnd_pcm_msg_pending_num() - Returns the number of pending I/O messages. * @vss: VirtIO substream. @@ -309,6 +336,8 @@ static void virtsnd_pcm_msg_complete(struct virtio_pcm_msg *msg, if (vss->hw_ptr >= vss->buffer_bytes) vss->hw_ptr -= vss->buffer_bytes; + msg->length = 0; + vss->xfer_xrun = false; vss->msg_count--; @@ -320,8 +349,6 @@ static void virtsnd_pcm_msg_complete(struct virtio_pcm_msg *msg, le32_to_cpu(msg->status.latency_bytes)); schedule_work(&vss->elapsed_period); - - virtsnd_pcm_msg_send(vss); } else if (!vss->msg_count) { wake_up_all(&vss->msg_empty); } diff --git a/sound/virtio/virtio_pcm_ops.c b/sound/virtio/virtio_pcm_ops.c index f8bfb87624be..4569b285f520 100644 --- a/sound/virtio/virtio_pcm_ops.c +++ b/sound/virtio/virtio_pcm_ops.c @@ -282,7 +282,6 @@ static int virtsnd_pcm_prepare(struct snd_pcm_substream *substream) vss->buffer_bytes = snd_pcm_lib_buffer_bytes(substream); vss->hw_ptr = 0; - vss->msg_last_enqueued = -1; } else { struct snd_pcm_runtime *runtime = substream->runtime; unsigned int buffer_bytes = snd_pcm_lib_buffer_bytes(substream); @@ -324,7 +323,7 @@ static int virtsnd_pcm_trigger(struct snd_pcm_substream *substream, int command) struct virtio_snd_queue *queue; struct virtio_snd_msg *msg; unsigned long flags; - int rc; + int rc = 0; switch (command) { case SNDRV_PCM_TRIGGER_START: @@ -333,7 +332,8 @@ static int virtsnd_pcm_trigger(struct snd_pcm_substream *substream, int command) spin_lock_irqsave(&queue->lock, flags); spin_lock(&vss->lock); - rc = virtsnd_pcm_msg_send(vss); + if (vss->direction == SNDRV_PCM_STREAM_CAPTURE) + rc = virtsnd_pcm_msg_send(vss, 0, vss->buffer_bytes); if (!rc) vss->xfer_enabled = true; spin_unlock(&vss->lock); @@ -450,15 +450,70 @@ virtsnd_pcm_pointer(struct snd_pcm_substream *substream) return hw_ptr; } +static int virtsnd_pcm_pb_silence(struct snd_pcm_substream *substream, + int channel, unsigned long pos, + unsigned long bytes) +{ + struct virtio_pcm_substream *vss = snd_pcm_substream_chip(substream); + struct snd_pcm_runtime *runtime = substream->runtime; + + snd_pcm_format_set_silence(runtime->format, runtime->dma_area + pos, + bytes_to_samples(runtime, bytes)); + + return virtsnd_pcm_msg_send_locked(vss, pos, bytes); +} + +static int virtsnd_pcm_pb_copy(struct snd_pcm_substream *substream, int channel, + unsigned long pos, struct iov_iter *iter, + unsigned long bytes) +{ + struct virtio_pcm_substream *vss = snd_pcm_substream_chip(substream); + struct snd_pcm_runtime *runtime = substream->runtime; + + if (copy_from_iter(runtime->dma_area + pos, bytes, iter) != bytes) + return -EFAULT; + + return virtsnd_pcm_msg_send_locked(vss, pos, bytes); +} + +static int virtsnd_pcm_cp_copy(struct snd_pcm_substream *substream, int channel, + unsigned long pos, struct iov_iter *iter, + unsigned long bytes) +{ + struct virtio_pcm_substream *vss = snd_pcm_substream_chip(substream); + struct snd_pcm_runtime *runtime = substream->runtime; + + if (copy_to_iter(runtime->dma_area + pos, bytes, iter) != bytes) + return -EFAULT; + + return virtsnd_pcm_msg_send_locked(vss, pos, bytes); +} + /* PCM substream operators map. */ -const struct snd_pcm_ops virtsnd_pcm_ops = { - .open = virtsnd_pcm_open, - .close = virtsnd_pcm_close, - .ioctl = snd_pcm_lib_ioctl, - .hw_params = virtsnd_pcm_hw_params, - .hw_free = virtsnd_pcm_hw_free, - .prepare = virtsnd_pcm_prepare, - .trigger = virtsnd_pcm_trigger, - .sync_stop = virtsnd_pcm_sync_stop, - .pointer = virtsnd_pcm_pointer, +const struct snd_pcm_ops virtsnd_pcm_ops[] = { + { + .open = virtsnd_pcm_open, + .close = virtsnd_pcm_close, + .ioctl = snd_pcm_lib_ioctl, + .hw_params = virtsnd_pcm_hw_params, + .hw_free = virtsnd_pcm_hw_free, + .prepare = virtsnd_pcm_prepare, + .trigger = virtsnd_pcm_trigger, + .sync_stop = virtsnd_pcm_sync_stop, + .pointer = virtsnd_pcm_pointer, + .copy = virtsnd_pcm_pb_copy, + .fill_silence = virtsnd_pcm_pb_silence, + }, + { + .open = virtsnd_pcm_open, + .close = virtsnd_pcm_close, + .ioctl = snd_pcm_lib_ioctl, + .hw_params = virtsnd_pcm_hw_params, + .hw_free = virtsnd_pcm_hw_free, + .prepare = virtsnd_pcm_prepare, + .trigger = virtsnd_pcm_trigger, + .sync_stop = virtsnd_pcm_sync_stop, + .pointer = virtsnd_pcm_pointer, + .copy = virtsnd_pcm_cp_copy, + }, };
This commit replaces the mmap mechanism with the copy() and fill_silence() callbacks for both capturing and playback for the virtio-sound driver. This change is required to prevent the updating of the content of a buffer that is already in the available ring. The current mechanism splits a dma buffer into descriptors that are exposed to the device. This dma buffer is shared with the user application. When the device consumes a buffer, the driver moves the request from the used ring to available ring. The driver exposes the buffer to the device without knowing if the content has been updated from the user. The section 2.8.21.1 of the virtio spec states that: "The device MAY access the descriptor chains the driver created and the memory they refer to immediately". If the device picks up buffers from the available ring just after it is notified, it happens that the content may be old. By providing the copy() callback, the driver first updates the content of the buffer, and then, exposes the buffer to the device by enqueuing it in the available ring. Thus, device always picks up a buffer that is updated. During copy(), the number of requests enqueued depends on the "pos" and "bytes" arguments. The length of each request is period_size bytes. For capturing, the driver starts by exposing all the available buffers to device. After device updates the content of a buffer, it enqueues it in the used ring. It is only after the copy() for capturing is issued that the driver re-enqueues the buffer in the available ring. Co-developed-by: Anton Yakovlev <anton.yakovlev@opensynergy.com> Signed-off-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com> --- Changelog: v1 -> v2: * Use snd_pcm_set_managed_buffer_all()for buffer allocation/freeing. * Make virtsnd_pcm_msg_send() generic by specifying the offset and size for the modified part of the buffer; this way no assumptions need to be made. * Disable SNDRV_PCM_INFO_NO_REWINDS since now only sequential reading/writing of frames is supported. * Correct comment at virtsnd_pcm_msg_send(). * v1 patch at: https://lore.kernel.org/lkml/20231016151000.GE119987@fedora/t/ sound/virtio/virtio_pcm.c | 7 ++- sound/virtio/virtio_pcm.h | 9 ++-- sound/virtio/virtio_pcm_msg.c | 93 ++++++++++++++++++++++------------- sound/virtio/virtio_pcm_ops.c | 81 +++++++++++++++++++++++++----- 4 files changed, 137 insertions(+), 53 deletions(-) base-commit: 8a749fd1a8720d4619c91c8b6e7528c0a355c0aa