2021-12-01 11:20:30

by Will Deacon

Subject: [PATCH] virtio_ring: Fix querying of maximum DMA mapping size for virtio device

virtio_max_dma_size() returns the maximum DMA mapping size of the virtio
device by querying dma_max_mapping_size() for the device when the DMA
API is in use for the vring. Unfortunately, the device passed is
initialised by register_virtio_device() and does not inherit the DMA
configuration from its parent, resulting in SWIOTLB errors when bouncing
is enabled and the default 256K mapping limit (IO_TLB_SEGSIZE) is not
respected:

| virtio-pci 0000:00:01.0: swiotlb buffer is full (sz: 294912 bytes), total 1024 (slots), used 725 (slots)

Follow the pattern used elsewhere in the virtio_ring code when calling
into the DMA layer and pass the parent device to dma_max_mapping_size()
instead.

Cc: Marc Zyngier <[email protected]>
Cc: Quentin Perret <[email protected]>
Cc: "Michael S. Tsirkin" <[email protected]>
Cc: Jason Wang <[email protected]>
Signed-off-by: Will Deacon <[email protected]>
---
drivers/virtio/virtio_ring.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index 6d2614e34470..028b05d44546 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -268,7 +268,7 @@ size_t virtio_max_dma_size(struct virtio_device *vdev)
size_t max_segment_size = SIZE_MAX;

if (vring_use_dma_api(vdev))
- max_segment_size = dma_max_mapping_size(&vdev->dev);
+ max_segment_size = dma_max_mapping_size(vdev->dev.parent);

return max_segment_size;
}
--
2.34.0.rc2.393.gf8c9666880-goog

2021-12-02 03:12:41

by Jason Wang

Subject: Re: [PATCH] virtio_ring: Fix querying of maximum DMA mapping size for virtio device

On Wed, Dec 1, 2021 at 7:20 PM Will Deacon <[email protected]> wrote:
>
> virtio_max_dma_size() returns the maximum DMA mapping size of the virtio
> device by querying dma_max_mapping_size() for the device when the DMA
> API is in use for the vring. Unfortunately, the device passed is
> initialised by register_virtio_device() and does not inherit the DMA
> configuration from its parent, resulting in SWIOTLB errors when bouncing
> is enabled and the default 256K mapping limit (IO_TLB_SEGSIZE) is not
> respected:
>
> | virtio-pci 0000:00:01.0: swiotlb buffer is full (sz: 294912 bytes), total 1024 (slots), used 725 (slots)
>
> Follow the pattern used elsewhere in the virtio_ring code when calling
> into the DMA layer and pass the parent device to dma_max_mapping_size()
> instead.
>
> Cc: Marc Zyngier <[email protected]>
> Cc: Quentin Perret <[email protected]>
> Cc: "Michael S. Tsirkin" <[email protected]>
> Cc: Jason Wang <[email protected]>
> Signed-off-by: Will Deacon <[email protected]>

Acked-by: Jason Wang <[email protected]>

> ---
> drivers/virtio/virtio_ring.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 6d2614e34470..028b05d44546 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -268,7 +268,7 @@ size_t virtio_max_dma_size(struct virtio_device *vdev)
> size_t max_segment_size = SIZE_MAX;
>
> if (vring_use_dma_api(vdev))
> - max_segment_size = dma_max_mapping_size(&vdev->dev);
> + max_segment_size = dma_max_mapping_size(vdev->dev.parent);
>
> return max_segment_size;
> }
> --
> 2.34.0.rc2.393.gf8c9666880-goog
>

2021-12-03 15:50:46

by Suzuki K Poulose

Subject: Re: [PATCH] virtio_ring: Fix querying of maximum DMA mapping size for virtio device

On 01/12/2021 11:20, Will Deacon wrote:
> virtio_max_dma_size() returns the maximum DMA mapping size of the virtio
> device by querying dma_max_mapping_size() for the device when the DMA
> API is in use for the vring. Unfortunately, the device passed is
> initialised by register_virtio_device() and does not inherit the DMA
> configuration from its parent, resulting in SWIOTLB errors when bouncing
> is enabled and the default 256K mapping limit (IO_TLB_SEGSIZE) is not
> respected:
>
> | virtio-pci 0000:00:01.0: swiotlb buffer is full (sz: 294912 bytes), total 1024 (slots), used 725 (slots)
>
> Follow the pattern used elsewhere in the virtio_ring code when calling
> into the DMA layer and pass the parent device to dma_max_mapping_size()
> instead.
>
> Cc: Marc Zyngier <[email protected]>
> Cc: Quentin Perret <[email protected]>
> Cc: "Michael S. Tsirkin" <[email protected]>
> Cc: Jason Wang <[email protected]>
> Signed-off-by: Will Deacon <[email protected]>

We hit a similar problem and ended up in the same patch, a bit late [0].

FWIW:

Tested-by: Suzuki K Poulose <[email protected]>

[0]
https://lkml.kernel.org/r/[email protected]


> ---
> drivers/virtio/virtio_ring.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 6d2614e34470..028b05d44546 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -268,7 +268,7 @@ size_t virtio_max_dma_size(struct virtio_device *vdev)
> size_t max_segment_size = SIZE_MAX;
>
> if (vring_use_dma_api(vdev))
> - max_segment_size = dma_max_mapping_size(&vdev->dev);
> + max_segment_size = dma_max_mapping_size(vdev->dev.parent);
>
> return max_segment_size;
> }
>