On Tue, Dec 07, 2021 at 03:51:45PM +0800, 王贇 wrote:
> We observed issues like:
> virtio-pci 0000:14:00.0: platform bug: legacy virtio-mmio must
> not be used with RAM above 0x4000GB
>
> when we have a legacy pci device which desired 32bit-pfn vq
> but gain 64bit-pfn instead, lead into the failure of probe.
>
> vring_use_dma_api() is playing the key role in here, to help the
> allocation process understand which kind of vq it should alloc,
> however, it failed to take care the legacy pci device, which only
> have 32bit feature flag and can never have VIRTIO_F_ACCESS_PLATFORM
> setted.
>
> This patch introduce force_dma flag to help vring_use_dma_api()
> understanding the requirement better, to avoid the failing.
>
> Signed-off-by: Michael Wang <[email protected]>
This will break configs where the device appears behind
a virtual iommu, so this won't fly.
Just make your device support 1.0, eh?
> ---
> drivers/virtio/virtio_pci_legacy.c | 10 ++++++++++
> drivers/virtio/virtio_ring.c | 3 +++
> include/linux/virtio.h | 1 +
> 3 files changed, 14 insertions(+)
>
> diff --git a/drivers/virtio/virtio_pci_legacy.c
> b/drivers/virtio/virtio_pci_legacy.c
> index d62e983..11f2ebf 100644
> --- a/drivers/virtio/virtio_pci_legacy.c
> +++ b/drivers/virtio/virtio_pci_legacy.c
> @@ -263,6 +263,16 @@ int virtio_pci_legacy_probe(struct virtio_pci_device
> *vp_dev)
> vp_dev->setup_vq = setup_vq;
> vp_dev->del_vq = del_vq;
>
> + /*
> + * The legacy pci device requre 32bit-pfn vq,
> + * or setup_vq() will failed.
> + *
> + * Thus we make sure vring_use_dma_api() will
> + * return true during the allocation by marking
> + * force_dma here.
> + */
> + vp_dev->vdev.force_dma = true;
> +
> return 0;
>
> err_iomap:
> diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
> index 3035bb6..6562e01 100644
> --- a/drivers/virtio/virtio_ring.c
> +++ b/drivers/virtio/virtio_ring.c
> @@ -245,6 +245,9 @@ static inline bool virtqueue_use_indirect(struct
> virtqueue *_vq,
>
> static bool vring_use_dma_api(struct virtio_device *vdev)
> {
> + if (vdev->force_dma)
> + return true;
> +
> if (!virtio_has_dma_quirk(vdev))
> return true;
>
> diff --git a/include/linux/virtio.h b/include/linux/virtio.h
> index 41edbc0..a4eb29d 100644
> --- a/include/linux/virtio.h
> +++ b/include/linux/virtio.h
> @@ -109,6 +109,7 @@ struct virtio_device {
> bool failed;
> bool config_enabled;
> bool config_change_pending;
> + bool force_dma;
> spinlock_t config_lock;
> spinlock_t vqs_list_lock; /* Protects VQs list access */
> struct device dev;
> --
> 1.8.3.1
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