virtio: Use bounce buffers when VIRTIO_F_IOMMU_PLATFORM is set

Devices advertising the VIRTIO_F_IOMMU_PLATFORM feature require
platform-specific handling to configure their DMA transactions.

When handling virtio descriptors for such a device, use bounce
buffers to ensure that the underlying buffers are always aligned
to and padded to PAGE_SIZE in preparation for platform specific
handling at page granularity.

Signed-off-by: Will Deacon <willdeacon@google.com>
[ Paul: pick from the Android tree. Rebase to the upstream ]
Signed-off-by: Ying-Chun Liu (PaulLiu) <paul.liu@linaro.org>
Cc: Bin Meng <bmeng.cn@gmail.com>
Link: https://android.googlesource.com/platform/external/u-boot/+/1eff171e613ee67dca71dbe97be7282e2db17011
Reviewed-by: Simon Glass <sjg@chromium.org>

diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index de75786ca767f50b15daea9fddccad9161827c17..c9adcce5c09ba18892fd8ec8291fcefa8b19041e 100644 (file)
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -28,14 +28,51 @@ static void virtio_free_pages(struct udevice *vdev, void *ptr, u32 npages)
        free(ptr);
 }
 
+static int __bb_force_page_align(struct bounce_buffer *state)
+{
+       const ulong align_mask = PAGE_SIZE - 1;
+
+       if ((ulong)state->user_buffer & align_mask)
+               return 0;
+
+       if (state->len != state->len_aligned)
+               return 0;
+
+       return 1;
+}
+
 static unsigned int virtqueue_attach_desc(struct virtqueue *vq, unsigned int i,
                                          struct virtio_sg *sg, u16 flags)
 {
        struct vring_desc_shadow *desc_shadow = &vq->vring_desc_shadow[i];
        struct vring_desc *desc = &vq->vring.desc[i];
+       void *addr;
+
+       if (IS_ENABLED(CONFIG_BOUNCE_BUFFER) && vq->vring.bouncebufs) {
+               struct bounce_buffer *bb = &vq->vring.bouncebufs[i];
+               unsigned int bbflags;
+               int ret;
+
+               if (flags & VRING_DESC_F_WRITE)
+                       bbflags = GEN_BB_WRITE;
+               else
+                       bbflags = GEN_BB_READ;
+
+               ret = bounce_buffer_start_extalign(bb, sg->addr, sg->length,
+                                                  bbflags, PAGE_SIZE,
+                                                  __bb_force_page_align);
+               if (ret) {
+                       debug("%s: failed to allocate bounce buffer (length 0x%zx)\n",
+                             vq->vdev->name, sg->length);
+               }
+
+               addr = bb->bounce_buffer;
+       } else {
+               addr = sg->addr;
+       }
 
        /* Update the shadow descriptor. */
-       desc_shadow->addr = (u64)(uintptr_t)sg->addr;
+       desc_shadow->addr = (u64)(uintptr_t)addr;
        desc_shadow->len = sg->length;
        desc_shadow->flags = flags;
 
@@ -50,6 +87,15 @@ static unsigned int virtqueue_attach_desc(struct virtqueue *vq, unsigned int i,
 
 static void virtqueue_detach_desc(struct virtqueue *vq, unsigned int idx)
 {
+       struct vring_desc *desc = &vq->vring.desc[idx];
+       struct bounce_buffer *bb;
+
+       if (!IS_ENABLED(CONFIG_BOUNCE_BUFFER) || !vq->vring.bouncebufs)
+               return;
+
+       bb = &vq->vring.bouncebufs[idx];
+       bounce_buffer_stop(bb);
+       desc->addr = cpu_to_virtio64(vq->vdev, (u64)(uintptr_t)bb->user_buffer);
 }
 
 int virtqueue_add(struct virtqueue *vq, struct virtio_sg *sgs[],