Re: [PATCH v3 4/8] vringh: support VA with iotlb

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On Thu, Mar 23, 2023 at 09:09:14AM +0100, Eugenio Perez Martin wrote:
On Tue, Mar 21, 2023 at 4:43 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:
    v3:
    - refactored avoiding code duplication [Eugenio]
    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            | 153 +++++++++++++++++++++++-------
 4 files changed, 127 insertions(+), 37 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 520646ae7fa0..dfd0e000217b 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 eea23c630f7c..47cdf2a1f5b8 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,
@@ -92,7 +92,7 @@ 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..72c88519329a 100644
--- a/drivers/vhost/vringh.c
+++ b/drivers/vhost/vringh.c
@@ -1094,10 +1094,18 @@ EXPORT_SYMBOL(vringh_need_notify_kern);

 #if IS_REACHABLE(CONFIG_VHOST_IOTLB)

+struct iotlb_vec {
+       union {
+               struct iovec *iovec;
+               struct bio_vec *bvec;
+       } iov;
+       size_t count;
+       bool is_iovec;
+};
+
 static int iotlb_translate(const struct vringh *vrh,
                           u64 addr, u64 len, u64 *translated,
-                          struct bio_vec iov[],
-                          int iov_size, u32 perm)
+                          struct iotlb_vec *ivec, u32 perm)
 {
        struct vhost_iotlb_map *map;
        struct vhost_iotlb *iotlb = vrh->iotlb;
@@ -1107,9 +1115,9 @@ static int iotlb_translate(const struct vringh *vrh,
        spin_lock(vrh->iotlb_lock);

        while (len > s) {
-               u64 size, pa, pfn;
+               u64 size;

-               if (unlikely(ret >= iov_size)) {
+               if (unlikely(ret >= ivec->count)) {
                        ret = -ENOBUFS;
                        break;
                }
@@ -1124,10 +1132,22 @@ static int iotlb_translate(const struct vringh *vrh,
                }

                size = map->size - addr + map->start;
-               pa = map->addr + addr - map->start;
-               pfn = pa >> PAGE_SHIFT;
-               bvec_set_page(&iov[ret], pfn_to_page(pfn), min(len - s, size),
-                             pa & (PAGE_SIZE - 1));
+               if (ivec->is_iovec) {
+                       struct iovec *iovec = ivec->iov.iovec;
+
+                       iovec[ret].iov_len = min(len - s, size);
+                       iovec[ret].iov_base = (void __user *)(unsigned long)

s/unsigned long/uintptr_t ?


yep, good catch!

As I wrote to Jason, I think I'll take it out of the if and just declare an uintptr_t variable, since I'm using it also in the else branch.



+                                             (map->addr + addr - map->start);
+               } else {
+                       u64 pa = map->addr + addr - map->start;
+                       u64 pfn = pa >> PAGE_SHIFT;
+                       struct bio_vec *bvec = ivec->iov.bvec;
+
+                       bvec_set_page(&bvec[ret], pfn_to_page(pfn),
+                                     min(len - s, size),
+                                     pa & (PAGE_SIZE - 1));
+               }
+
                s += size;
                addr += size;
                ++ret;
@@ -1141,26 +1161,42 @@ static int iotlb_translate(const struct vringh *vrh,
        return ret;
 }

+#define IOTLB_IOV_SIZE 16

I'm fine with defining here, but maybe it is better to isolate the
change in a previous patch or reuse another well known macro?

Yep, good point!

Do you have any well known macro to suggest?


Other looks good, and I agree with Jason's comments so even if the
macro declaration is not moved:

Acked-by: Eugenio Pérez <eperezma@xxxxxxxxxx>

Thanks,
Stefano

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