Re: [PATCH v2] virtio_console: allocate inbufs in add_port() only if it is needed
On Wed, Nov 13, 2019 at 05:37:34PM +0100, Laurent Vivier wrote:
> On 13/11/2019 16:22, Michael S. Tsirkin wrote:
> > On Wed, Nov 13, 2019 at 10:21:11AM -0500, Michael S. Tsirkin wrote:
> >> On Wed, Nov 13, 2019 at 04:00:56PM +0100, Laurent Vivier wrote:
> >>> When we hot unplug a virtserialport and then try to hot plug again,
> >>> it fails:
> >>>
> >>> (qemu) chardev-add socket,id=serial0,path=/tmp/serial0,server,nowait
> >>> (qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\
> >>> chardev=serial0,id=serial0,name=serial0
> >>> (qemu) device_del serial0
> >>> (qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\
> >>> chardev=serial0,id=serial0,name=serial0
> >>> kernel error:
> >>> virtio-ports vport2p2: Error allocating inbufs
> >>> qemu error:
> >>> virtio-serial-bus: Guest failure in adding port 2 for device \
> >>> virtio-serial0.0
> >>>
> >>> This happens because buffers for the in_vq are allocated when the port is
> >>> added but are not released when the port is unplugged.
> >>>
> >>> They are only released when virtconsole is removed (see a7a69ec0d8e4)
> >>>
> >>> To avoid the problem and to be symmetric, we could allocate all the
> >>> buffers
> >>> in init_vqs() as they are released in remove_vqs(), but it sounds like
> >>> a waste of memory.
> >>>
> >>> Rather than that, this patch changes add_port() logic to ignore ENOSPC
> >>> error in fill_queue(), which means queue has already been filled.
> >>>
> >>> Fixes: a7a69ec0d8e4 ("virtio_console: free buffers after reset")
> >>> Cc: m...@redhat.com
> >>> Cc: sta...@vger.kernel.org
> >>> Signed-off-by: Laurent Vivier
> >>> ---
> >>>
> >>> Notes:
> >>> v2: making fill_queue return int and testing return code for -ENOSPC
> >>>
> >>> drivers/char/virtio_console.c | 24 +---
> >>> 1 file changed, 9 insertions(+), 15 deletions(-)
> >>>
> >>> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> >>> index 7270e7b69262..9e6534fd1aa4 100644
> >>> --- a/drivers/char/virtio_console.c
> >>> +++ b/drivers/char/virtio_console.c
> >>> @@ -1325,24 +1325,24 @@ static void set_console_size(struct port *port,
> >>> u16 rows, u16 cols)
> >>> port->cons.ws.ws_col = cols;
> >>> }
> >>>
> >>> -static unsigned int fill_queue(struct virtqueue *vq, spinlock_t *lock)
> >>> +static int fill_queue(struct virtqueue *vq, spinlock_t *lock)
> >>> {
> >>> struct port_buffer *buf;
> >>> - unsigned int nr_added_bufs;
> >>> + int nr_added_bufs;
> >>> int ret;
> >>>
> >>> nr_added_bufs = 0;
> >>> do {
> >>> buf = alloc_buf(vq->vdev, PAGE_SIZE, 0);
> >>> if (!buf)
> >>> - break;
> >>> + return -ENOMEM;
> >>>
> >>> spin_lock_irq(lock);
> >>> ret = add_inbuf(vq, buf);
> >>> if (ret < 0) {
> >>> spin_unlock_irq(lock);
> >>> free_buf(buf, true);
> >>> - break;
> >>> + return ret;
> >>> }
> >>> nr_added_bufs++;
> >>> spin_unlock_irq(lock);
> >
> > So actually, how about handling ENOSPC specially here, and
> > returning success? After all queue is full as requested ...
>
> I think it's interesting to return -ENOSPC to manage it as a real error
> in virtcons_probe() as in this function the queue should not be already
> full (is this right?) and to return the real error code.
>
> Thanks,
> Laurent
OK then. Pls add comments.
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Re: [PATCH v2] virtio_console: allocate inbufs in add_port() only if it is needed
On 13/11/2019 16:22, Michael S. Tsirkin wrote:
> On Wed, Nov 13, 2019 at 10:21:11AM -0500, Michael S. Tsirkin wrote:
>> On Wed, Nov 13, 2019 at 04:00:56PM +0100, Laurent Vivier wrote:
>>> When we hot unplug a virtserialport and then try to hot plug again,
>>> it fails:
>>>
>>> (qemu) chardev-add socket,id=serial0,path=/tmp/serial0,server,nowait
>>> (qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\
>>> chardev=serial0,id=serial0,name=serial0
>>> (qemu) device_del serial0
>>> (qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\
>>> chardev=serial0,id=serial0,name=serial0
>>> kernel error:
>>> virtio-ports vport2p2: Error allocating inbufs
>>> qemu error:
>>> virtio-serial-bus: Guest failure in adding port 2 for device \
>>> virtio-serial0.0
>>>
>>> This happens because buffers for the in_vq are allocated when the port is
>>> added but are not released when the port is unplugged.
>>>
>>> They are only released when virtconsole is removed (see a7a69ec0d8e4)
>>>
>>> To avoid the problem and to be symmetric, we could allocate all the buffers
>>> in init_vqs() as they are released in remove_vqs(), but it sounds like
>>> a waste of memory.
>>>
>>> Rather than that, this patch changes add_port() logic to ignore ENOSPC
>>> error in fill_queue(), which means queue has already been filled.
>>>
>>> Fixes: a7a69ec0d8e4 ("virtio_console: free buffers after reset")
>>> Cc: m...@redhat.com
>>> Cc: sta...@vger.kernel.org
>>> Signed-off-by: Laurent Vivier
>>> ---
>>>
>>> Notes:
>>> v2: making fill_queue return int and testing return code for -ENOSPC
>>>
>>> drivers/char/virtio_console.c | 24 +---
>>> 1 file changed, 9 insertions(+), 15 deletions(-)
>>>
>>> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
>>> index 7270e7b69262..9e6534fd1aa4 100644
>>> --- a/drivers/char/virtio_console.c
>>> +++ b/drivers/char/virtio_console.c
>>> @@ -1325,24 +1325,24 @@ static void set_console_size(struct port *port, u16
>>> rows, u16 cols)
>>> port->cons.ws.ws_col = cols;
>>> }
>>>
>>> -static unsigned int fill_queue(struct virtqueue *vq, spinlock_t *lock)
>>> +static int fill_queue(struct virtqueue *vq, spinlock_t *lock)
>>> {
>>> struct port_buffer *buf;
>>> - unsigned int nr_added_bufs;
>>> + int nr_added_bufs;
>>> int ret;
>>>
>>> nr_added_bufs = 0;
>>> do {
>>> buf = alloc_buf(vq->vdev, PAGE_SIZE, 0);
>>> if (!buf)
>>> - break;
>>> + return -ENOMEM;
>>>
>>> spin_lock_irq(lock);
>>> ret = add_inbuf(vq, buf);
>>> if (ret < 0) {
>>> spin_unlock_irq(lock);
>>> free_buf(buf, true);
>>> - break;
>>> + return ret;
>>> }
>>> nr_added_bufs++;
>>> spin_unlock_irq(lock);
>
> So actually, how about handling ENOSPC specially here, and
> returning success? After all queue is full as requested ...
I think it's interesting to return -ENOSPC to manage it as a real error
in virtcons_probe() as in this function the queue should not be already
full (is this right?) and to return the real error code.
Thanks,
Laurent
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Re: [PATCH v2] virtio_console: allocate inbufs in add_port() only if it is needed
On Wed, Nov 13, 2019 at 10:21:11AM -0500, Michael S. Tsirkin wrote:
> On Wed, Nov 13, 2019 at 04:00:56PM +0100, Laurent Vivier wrote:
> > When we hot unplug a virtserialport and then try to hot plug again,
> > it fails:
> >
> > (qemu) chardev-add socket,id=serial0,path=/tmp/serial0,server,nowait
> > (qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\
> > chardev=serial0,id=serial0,name=serial0
> > (qemu) device_del serial0
> > (qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\
> > chardev=serial0,id=serial0,name=serial0
> > kernel error:
> > virtio-ports vport2p2: Error allocating inbufs
> > qemu error:
> > virtio-serial-bus: Guest failure in adding port 2 for device \
> > virtio-serial0.0
> >
> > This happens because buffers for the in_vq are allocated when the port is
> > added but are not released when the port is unplugged.
> >
> > They are only released when virtconsole is removed (see a7a69ec0d8e4)
> >
> > To avoid the problem and to be symmetric, we could allocate all the buffers
> > in init_vqs() as they are released in remove_vqs(), but it sounds like
> > a waste of memory.
> >
> > Rather than that, this patch changes add_port() logic to ignore ENOSPC
> > error in fill_queue(), which means queue has already been filled.
> >
> > Fixes: a7a69ec0d8e4 ("virtio_console: free buffers after reset")
> > Cc: m...@redhat.com
> > Cc: sta...@vger.kernel.org
> > Signed-off-by: Laurent Vivier
> > ---
> >
> > Notes:
> > v2: making fill_queue return int and testing return code for -ENOSPC
> >
> > drivers/char/virtio_console.c | 24 +---
> > 1 file changed, 9 insertions(+), 15 deletions(-)
> >
> > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> > index 7270e7b69262..9e6534fd1aa4 100644
> > --- a/drivers/char/virtio_console.c
> > +++ b/drivers/char/virtio_console.c
> > @@ -1325,24 +1325,24 @@ static void set_console_size(struct port *port, u16
> > rows, u16 cols)
> > port->cons.ws.ws_col = cols;
> > }
> >
> > -static unsigned int fill_queue(struct virtqueue *vq, spinlock_t *lock)
> > +static int fill_queue(struct virtqueue *vq, spinlock_t *lock)
> > {
> > struct port_buffer *buf;
> > - unsigned int nr_added_bufs;
> > + int nr_added_bufs;
> > int ret;
> >
> > nr_added_bufs = 0;
> > do {
> > buf = alloc_buf(vq->vdev, PAGE_SIZE, 0);
> > if (!buf)
> > - break;
> > + return -ENOMEM;
> >
> > spin_lock_irq(lock);
> > ret = add_inbuf(vq, buf);
> > if (ret < 0) {
> > spin_unlock_irq(lock);
> > free_buf(buf, true);
> > - break;
> > + return ret;
> > }
> > nr_added_bufs++;
> > spin_unlock_irq(lock);
So actually, how about handling ENOSPC specially here, and
returning success? After all queue is full as requested ...
> > @@ -1362,7 +1362,6 @@ static int add_port(struct ports_device *portdev, u32
> > id)
> > char debugfs_name[16];
> > struct port *port;
> > dev_t devt;
> > - unsigned int nr_added_bufs;
> > int err;
> >
> > port = kmalloc(sizeof(*port), GFP_KERNEL);
> > @@ -1421,11 +1420,9 @@ static int add_port(struct ports_device *portdev,
> > u32 id)
> > spin_lock_init(>outvq_lock);
> > init_waitqueue_head(>waitqueue);
> >
> > - /* Fill the in_vq with buffers so the host can send us data. */
> > - nr_added_bufs = fill_queue(port->in_vq, >inbuf_lock);
> > - if (!nr_added_bufs) {
> > + err = fill_queue(port->in_vq, >inbuf_lock);
> > + if (err < 0 && err != -ENOSPC) {
> > dev_err(port->dev, "Error allocating inbufs\n");
> > - err = -ENOMEM;
> > goto free_device;
> > }
> >
>
> Pls add a comment explaining that -ENOSPC happens when
> queue already has buffers (e.g. from previous detach).
>
>
> > @@ -2059,14 +2056,11 @@ static int virtcons_probe(struct virtio_device
> > *vdev)
> > INIT_WORK(>control_work, _work_handler);
> >
> > if (multiport) {
> > - unsigned int nr_added_bufs;
> > -
> > spin_lock_init(>c_ivq_lock);
> > spin_lock_init(>c_ovq_lock);
> >
> > - nr_added_bufs = fill_queue(portdev->c_ivq,
> > - >c_ivq_lock);
> > - if (!nr_added_bufs) {
> > + err = fill_queue(portdev->c_ivq, >c_ivq_lock);
> > + if (err < 0) {
> > dev_err(>dev,
> > "Error allocating buffers for control queue\n");
> > /*
> > @@ -2077,7 +2071,7 @@ static int virtcons_probe(struct virtio_device *vdev)
> >VIRTIO_CONSOLE_DEVICE_READY, 0);
> > /* Device was functional: we need full cleanup. */
> > virtcons_remove(vdev);
> >
Re: [PATCH v2] virtio_console: allocate inbufs in add_port() only if it is needed
On Wed, Nov 13, 2019 at 04:00:56PM +0100, Laurent Vivier wrote:
> When we hot unplug a virtserialport and then try to hot plug again,
> it fails:
>
> (qemu) chardev-add socket,id=serial0,path=/tmp/serial0,server,nowait
> (qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\
> chardev=serial0,id=serial0,name=serial0
> (qemu) device_del serial0
> (qemu) device_add virtserialport,bus=virtio-serial0.0,nr=2,\
> chardev=serial0,id=serial0,name=serial0
> kernel error:
> virtio-ports vport2p2: Error allocating inbufs
> qemu error:
> virtio-serial-bus: Guest failure in adding port 2 for device \
> virtio-serial0.0
>
> This happens because buffers for the in_vq are allocated when the port is
> added but are not released when the port is unplugged.
>
> They are only released when virtconsole is removed (see a7a69ec0d8e4)
>
> To avoid the problem and to be symmetric, we could allocate all the buffers
> in init_vqs() as they are released in remove_vqs(), but it sounds like
> a waste of memory.
>
> Rather than that, this patch changes add_port() logic to ignore ENOSPC
> error in fill_queue(), which means queue has already been filled.
>
> Fixes: a7a69ec0d8e4 ("virtio_console: free buffers after reset")
> Cc: m...@redhat.com
> Cc: sta...@vger.kernel.org
> Signed-off-by: Laurent Vivier
> ---
>
> Notes:
> v2: making fill_queue return int and testing return code for -ENOSPC
>
> drivers/char/virtio_console.c | 24 +---
> 1 file changed, 9 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> index 7270e7b69262..9e6534fd1aa4 100644
> --- a/drivers/char/virtio_console.c
> +++ b/drivers/char/virtio_console.c
> @@ -1325,24 +1325,24 @@ static void set_console_size(struct port *port, u16
> rows, u16 cols)
> port->cons.ws.ws_col = cols;
> }
>
> -static unsigned int fill_queue(struct virtqueue *vq, spinlock_t *lock)
> +static int fill_queue(struct virtqueue *vq, spinlock_t *lock)
> {
> struct port_buffer *buf;
> - unsigned int nr_added_bufs;
> + int nr_added_bufs;
> int ret;
>
> nr_added_bufs = 0;
> do {
> buf = alloc_buf(vq->vdev, PAGE_SIZE, 0);
> if (!buf)
> - break;
> + return -ENOMEM;
>
> spin_lock_irq(lock);
> ret = add_inbuf(vq, buf);
> if (ret < 0) {
> spin_unlock_irq(lock);
> free_buf(buf, true);
> - break;
> + return ret;
> }
> nr_added_bufs++;
> spin_unlock_irq(lock);
> @@ -1362,7 +1362,6 @@ static int add_port(struct ports_device *portdev, u32
> id)
> char debugfs_name[16];
> struct port *port;
> dev_t devt;
> - unsigned int nr_added_bufs;
> int err;
>
> port = kmalloc(sizeof(*port), GFP_KERNEL);
> @@ -1421,11 +1420,9 @@ static int add_port(struct ports_device *portdev, u32
> id)
> spin_lock_init(>outvq_lock);
> init_waitqueue_head(>waitqueue);
>
> - /* Fill the in_vq with buffers so the host can send us data. */
> - nr_added_bufs = fill_queue(port->in_vq, >inbuf_lock);
> - if (!nr_added_bufs) {
> + err = fill_queue(port->in_vq, >inbuf_lock);
> + if (err < 0 && err != -ENOSPC) {
> dev_err(port->dev, "Error allocating inbufs\n");
> - err = -ENOMEM;
> goto free_device;
> }
>
Pls add a comment explaining that -ENOSPC happens when
queue already has buffers (e.g. from previous detach).
> @@ -2059,14 +2056,11 @@ static int virtcons_probe(struct virtio_device *vdev)
> INIT_WORK(>control_work, _work_handler);
>
> if (multiport) {
> - unsigned int nr_added_bufs;
> -
> spin_lock_init(>c_ivq_lock);
> spin_lock_init(>c_ovq_lock);
>
> - nr_added_bufs = fill_queue(portdev->c_ivq,
> ->c_ivq_lock);
> - if (!nr_added_bufs) {
> + err = fill_queue(portdev->c_ivq, >c_ivq_lock);
> + if (err < 0) {
> dev_err(>dev,
> "Error allocating buffers for control queue\n");
> /*
> @@ -2077,7 +2071,7 @@ static int virtcons_probe(struct virtio_device *vdev)
> VIRTIO_CONSOLE_DEVICE_READY, 0);
> /* Device was functional: we need full cleanup. */
> virtcons_remove(vdev);
> - return -ENOMEM;
> + return err;
> }
> } else {
> /*
> --
> 2.23.0
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