From: "Michael S. Tsirkin" <mst@redhat.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Alexander Lobakin <alobakin@pm.me>, Amit Shah <amit@kernel.org>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Arnaud Pouliquen <arnaud.pouliquen@st.com>,
Suman Anna <s-anna@ti.com>,
Mathieu Poirier <mathieu.poirier@linaro.org>,
Bjorn Andersson <bjorn.andersson@linaro.org>,
Ohad Ben-Cohen <ohad@wizery.com>,
Jason Wang <jasowang@redhat.com>,
virtualization@lists.linux-foundation.org,
linux-remoteproc@vger.kernel.org, linux-kernel@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH virtio] virtio: virtio_console: fix DMA memory allocation for rproc serial
Date: Mon, 16 Nov 2020 07:25:31 -0500 [thread overview]
Message-ID: <20201116071910-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20201116091950.GA30524@infradead.org>
On Mon, Nov 16, 2020 at 09:19:50AM +0000, Christoph Hellwig wrote:
> I just noticed this showing up in Linus' tree and I'm not happy.
Are you sure? I think it's in next.
> This whole model of the DMA subdevices in remoteproc is simply broken.
>
> We really need to change the virtio code pass an expicit DMA device (
> similar to what e.g. the USB and RDMA code does), instead of faking up
> devices with broken adhoc inheritance of DMA properties and magic poking
> into device parent relationships.
OK but we do have a regression since 5.7 and this looks like
a fix appropriate for e.g. stable, right?
> Bjorn, I thought you were going to look into this a while ago?
>
>
> On Wed, Nov 04, 2020 at 03:31:36PM +0000, Alexander Lobakin wrote:
> > Since commit 086d08725d34 ("remoteproc: create vdev subdevice with
> > specific dma memory pool"), every remoteproc has a DMA subdevice
> > ("remoteprocX#vdevYbuffer") for each virtio device, which inherits
> > DMA capabilities from the corresponding platform device. This allowed
> > to associate different DMA pools with each vdev, and required from
> > virtio drivers to perform DMA operations with the parent device
> > (vdev->dev.parent) instead of grandparent (vdev->dev.parent->parent).
> >
> > virtio_rpmsg_bus was already changed in the same merge cycle with
> > commit d999b622fcfb ("rpmsg: virtio: allocate buffer from parent"),
> > but virtio_console did not. In fact, operations using the grandparent
> > worked fine while the grandparent was the platform device, but since
> > commit c774ad010873 ("remoteproc: Fix and restore the parenting
> > hierarchy for vdev") this was changed, and now the grandparent device
> > is the remoteproc device without any DMA capabilities.
> > So, starting v5.8-rc1 the following warning is observed:
> >
> > [ 2.483925] ------------[ cut here ]------------
> > [ 2.489148] WARNING: CPU: 3 PID: 101 at kernel/dma/mapping.c:427 0x80e7eee8
> > [ 2.489152] Modules linked in: virtio_console(+)
> > [ 2.503737] virtio_rpmsg_bus rpmsg_core
> > [ 2.508903]
> > [ 2.528898] <Other modules, stack and call trace here>
> > [ 2.913043]
> > [ 2.914907] ---[ end trace 93ac8746beab612c ]---
> > [ 2.920102] virtio-ports vport1p0: Error allocating inbufs
> >
> > kernel/dma/mapping.c:427 is:
> >
> > WARN_ON_ONCE(!dev->coherent_dma_mask);
> >
> > obviously because the grandparent now is remoteproc dev without any
> > DMA caps:
> >
> > [ 3.104943] Parent: remoteproc0#vdev1buffer, grandparent: remoteproc0
> >
> > Fix this the same way as it was for virtio_rpmsg_bus, using just the
> > parent device (vdev->dev.parent, "remoteprocX#vdevYbuffer") for DMA
> > operations.
> > This also allows now to reserve DMA pools/buffers for rproc serial
> > via Device Tree.
> >
> > Fixes: c774ad010873 ("remoteproc: Fix and restore the parenting hierarchy for vdev")
> > Cc: stable@vger.kernel.org # 5.1+
> > Signed-off-by: Alexander Lobakin <alobakin@pm.me>
> > ---
> > drivers/char/virtio_console.c | 8 ++++----
> > 1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
> > index a2da8f768b94..1836cc56e357 100644
> > --- a/drivers/char/virtio_console.c
> > +++ b/drivers/char/virtio_console.c
> > @@ -435,12 +435,12 @@ static struct port_buffer *alloc_buf(struct virtio_device *vdev, size_t buf_size
> > /*
> > * Allocate DMA memory from ancestor. When a virtio
> > * device is created by remoteproc, the DMA memory is
> > - * associated with the grandparent device:
> > - * vdev => rproc => platform-dev.
> > + * associated with the parent device:
> > + * virtioY => remoteprocX#vdevYbuffer.
> > */
> > - if (!vdev->dev.parent || !vdev->dev.parent->parent)
> > + buf->dev = vdev->dev.parent;
> > + if (!buf->dev)
> > goto free_buf;
> > - buf->dev = vdev->dev.parent->parent;
> >
> > /* Increase device refcnt to avoid freeing it */
> > get_device(buf->dev);
> > --
> > 2.29.2
> >
> >
> ---end quoted text---
next prev parent reply other threads:[~2020-11-16 12:38 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-04 15:31 [PATCH virtio] virtio: virtio_console: fix DMA memory allocation for rproc serial Alexander Lobakin
2020-11-04 18:21 ` Mathieu Poirier
2020-11-05 3:10 ` Jason Wang
2020-11-05 12:22 ` Alexander Lobakin
2020-11-09 6:04 ` Jason Wang
2020-11-16 9:19 ` Christoph Hellwig
2020-11-16 9:51 ` Michael S. Tsirkin
2020-11-16 16:27 ` Christoph Hellwig
2020-11-16 16:43 ` Alexander Lobakin
2020-11-16 10:46 ` Arnaud POULIQUEN
2020-11-16 16:28 ` Christoph Hellwig
2020-11-16 16:39 ` Christoph Hellwig
2020-11-17 14:00 ` Arnaud POULIQUEN
2020-11-17 14:02 ` Christoph Hellwig
2020-11-18 10:16 ` Michael S. Tsirkin
2020-11-16 12:25 ` Michael S. Tsirkin [this message]
2020-11-16 13:07 ` Alexander Lobakin
2020-11-16 13:12 ` Michael S. Tsirkin
2020-11-16 16:30 ` Christoph Hellwig
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