Messages in this thread | | | Subject | Re: [PATCH virtio] virtio: virtio_console: fix DMA memory allocation for rproc serial | From | Jason Wang <> | Date | Mon, 9 Nov 2020 14:04:24 +0800 |
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On 2020/11/5 下午8:22, Alexander Lobakin wrote: > From: Jason Wang <jasowang@redhat.com> > Date: Thu, 5 Nov 2020 11:10:24 +0800 > > Hi Jason, > >> On 2020/11/4 下午11:31, 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; >> >> I wonder it could be the right time to introduce dma_dev for virtio >> instead of depending on something magic via parent. > This patch are meant to hit RC window and stable trees as a fix of > the bug that is present since v5.8-rc1. So any new features are out > of scope of this particular fix.
Right.
> > The idea of DMAing through "dev->parent" is that "virtioX" itself is a > logical dev, not the real one, but its parent *is*. This logic is used > across the whole tree -- every subsystem creates its own logical device, > but drivers should always use the backing PCI/platform/etc. devices for > DMA operations, which represent the real hardware.
Yes, so what I meant is to use different variables for DMA and hierarchy. So it's the responsibility of the lower layer to pass a correct "dma_dev" to the upper layer instead of depending parent.
Anyway for this patch.
Acked-by: Jason Wang <jasowang@redhat.com>
Thanks
> >> (Btw I don't even notice that there's transport specific code in virtio >> console, it's better to avoid it) >> >> Thanks > Thanks, > Al > >>> /* Increase device refcnt to avoid freeing it */ >>> get_device(buf->dev);
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