Re: [PATCH v2 4/8] vringh: support VA with iotlb

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On Fri, Mar 03, 2023 at 03:38:57PM +0100, Eugenio Perez Martin wrote:
On Thu, Mar 2, 2023 at 12:35 PM Stefano Garzarella <sgarzare@xxxxxxxxxx> wrote:

vDPA supports the possibility to use user VA in the iotlb messages.
So, let's add support for user VA in vringh to use it in the vDPA
simulators.

Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
---

Notes:
    v2:
    - replace kmap_atomic() with kmap_local_page() [see previous patch]
    - fix cast warnings when build with W=1 C=1

 include/linux/vringh.h            |   5 +-
 drivers/vdpa/mlx5/net/mlx5_vnet.c |   2 +-
 drivers/vdpa/vdpa_sim/vdpa_sim.c  |   4 +-
 drivers/vhost/vringh.c            | 247 ++++++++++++++++++++++++------
 4 files changed, 205 insertions(+), 53 deletions(-)

diff --git a/include/linux/vringh.h b/include/linux/vringh.h
index 1991a02c6431..d39b9f2dcba0 100644
--- a/include/linux/vringh.h
+++ b/include/linux/vringh.h
@@ -32,6 +32,9 @@ struct vringh {
        /* Can we get away with weak barriers? */
        bool weak_barriers;

+       /* Use user's VA */
+       bool use_va;
+
        /* Last available index we saw (ie. where we're up to). */
        u16 last_avail_idx;

@@ -279,7 +282,7 @@ void vringh_set_iotlb(struct vringh *vrh, struct vhost_iotlb *iotlb,
                      spinlock_t *iotlb_lock);

 int vringh_init_iotlb(struct vringh *vrh, u64 features,
-                     unsigned int num, bool weak_barriers,
+                     unsigned int num, bool weak_barriers, bool use_va,
                      struct vring_desc *desc,
                      struct vring_avail *avail,
                      struct vring_used *used);
diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c b/drivers/vdpa/mlx5/net/mlx5_vnet.c
index 3a0e721aef05..babc8dd171a6 100644
--- a/drivers/vdpa/mlx5/net/mlx5_vnet.c
+++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c
@@ -2537,7 +2537,7 @@ static int setup_cvq_vring(struct mlx5_vdpa_dev *mvdev)

        if (mvdev->actual_features & BIT_ULL(VIRTIO_NET_F_CTRL_VQ))
                err = vringh_init_iotlb(&cvq->vring, mvdev->actual_features,
-                                       MLX5_CVQ_MAX_ENT, false,
+                                       MLX5_CVQ_MAX_ENT, false, false,
                                        (struct vring_desc *)(uintptr_t)cvq->desc_addr,
                                        (struct vring_avail *)(uintptr_t)cvq->driver_addr,
                                        (struct vring_used *)(uintptr_t)cvq->device_addr);
diff --git a/drivers/vdpa/vdpa_sim/vdpa_sim.c b/drivers/vdpa/vdpa_sim/vdpa_sim.c
index 6a0a65814626..481eb156658b 100644
--- a/drivers/vdpa/vdpa_sim/vdpa_sim.c
+++ b/drivers/vdpa/vdpa_sim/vdpa_sim.c
@@ -60,7 +60,7 @@ static void vdpasim_queue_ready(struct vdpasim *vdpasim, unsigned int idx)
        struct vdpasim_virtqueue *vq = &vdpasim->vqs[idx];
        uint16_t last_avail_idx = vq->vring.last_avail_idx;

-       vringh_init_iotlb(&vq->vring, vdpasim->features, vq->num, true,
+       vringh_init_iotlb(&vq->vring, vdpasim->features, vq->num, true, false,
                          (struct vring_desc *)(uintptr_t)vq->desc_addr,
                          (struct vring_avail *)
                          (uintptr_t)vq->driver_addr,
@@ -81,7 +81,7 @@ static void vdpasim_vq_reset(struct vdpasim *vdpasim,
        vq->cb = NULL;
        vq->private = NULL;
        vringh_init_iotlb(&vq->vring, vdpasim->dev_attr.supported_features,
-                         VDPASIM_QUEUE_MAX, false, NULL, NULL, NULL);
+                         VDPASIM_QUEUE_MAX, false, false, NULL, NULL, NULL);

        vq->vring.notify = NULL;
 }
diff --git a/drivers/vhost/vringh.c b/drivers/vhost/vringh.c
index 0ba3ef809e48..61c79cea44ca 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -1094,15 +1094,99 @@ EXPORT_SYMBOL(vringh_need_notify_kern);

 #if IS_REACHABLE(CONFIG_VHOST_IOTLB)

-static int iotlb_translate(const struct vringh *vrh,
-                          u64 addr, u64 len, u64 *translated,
-                          struct bio_vec iov[],
-                          int iov_size, u32 perm)
+static int iotlb_translate_va(const struct vringh *vrh,
+                             u64 addr, u64 len, u64 *translated,
+                             struct iovec iov[],
+                             int iov_size, u32 perm)
 {
        struct vhost_iotlb_map *map;
        struct vhost_iotlb *iotlb = vrh->iotlb;
+       u64 s = 0, last = addr + len - 1;
        int ret = 0;
+
+       spin_lock(vrh->iotlb_lock);
+
+       while (len > s) {
+               u64 size;
+
+               if (unlikely(ret >= iov_size)) {
+                       ret = -ENOBUFS;
+                       break;
+               }
+
+               map = vhost_iotlb_itree_first(iotlb, addr, last);
+               if (!map || map->start > addr) {
+                       ret = -EINVAL;
+                       break;
+               } else if (!(map->perm & perm)) {
+                       ret = -EPERM;
+                       break;
+               }
+
+               size = map->size - addr + map->start;
+               iov[ret].iov_len = min(len - s, size);
+               iov[ret].iov_base = (void __user *)(unsigned long)
+                                   (map->addr + addr - map->start);
+               s += size;
+               addr += size;
+               ++ret;
+       }
+
+       spin_unlock(vrh->iotlb_lock);
+
+       if (translated)
+               *translated = min(len, s);
+
+       return ret;
+}

It seems to me iotlb_translate_va and iotlb_translate_pa are very
similar, their only difference is that the argument is that iov is
iovec instead of bio_vec. And how to fill it, obviously.

It would be great to merge both functions, only differing with a
conditional on vrh->use_va, or generics, or similar. Or, if following
the style of the rest of vringh code, to provide a callback to fill
iovec (although I like conditional more).

However I cannot think of an easy way to perform that without long
macros or type erasure.

I agree and I tried, but then I got messed up and let it go.

But maybe with the callback it shouldn't be too messy, I can try it and
see what comes out :-)


+
+static inline int copy_from_va(const struct vringh *vrh, void *dst, void *src,
+                              u64 len, u64 *translated)
+{
+       struct iovec iov[16];
+       struct iov_iter iter;
+       int ret;
+
+       ret = iotlb_translate_va(vrh, (u64)(uintptr_t)src, len, translated, iov,
+                                ARRAY_SIZE(iov), VHOST_MAP_RO);
+       if (ret == -ENOBUFS)
+               ret = ARRAY_SIZE(iov);
+       else if (ret < 0)
+               return ret;
+
+       iov_iter_init(&iter, ITER_SOURCE, iov, ret, *translated);
+
+       return copy_from_iter(dst, *translated, &iter);

Maybe a good baby step for DRY is to return the iov_iter in
copy_from/to_va/pa here?

Good point! I'll try it.


But I'm ok with this version too.

Acked-by: Eugenio Pérez Martin <eperezma@xxxxxxxxxx>

Thanks for the review!
Stefano

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