On Tue, 2023-08-08 at 10:57 +0800, Jason Wang wrote:

On Thu, Aug 3, 2023 at 7:40 PM Dragos Tatulea [off-list ref] wrote:

quoted

On Thu, 2023-08-03 at 16:03 +0800, Jason Wang wrote:

quoted

On Thu, Aug 3, 2023 at 1:13 AM Dragos Tatulea [off-list ref] wrote:

quoted

The mr->initialized flag is shared between the control vq and data vq
part of the mr init/uninit. But if the control vq and data vq get placed
in different ASIDs, it can happen that initializing the control vq will
prevent the data vq mr from being initialized.

This patch consolidates the control and data vq init parts into their
own init functions. The mr->initialized will now be used for the data vq
only. The control vq currently doesn't need a flag.

The uninitializing part is also taken care of: mlx5_vdpa_destroy_mr got
split into data and control vq functions which are now also ASID aware.

Fixes: 8fcd20c30704 ("vdpa/mlx5: Support different address spaces for
control and data")
Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Reviewed-by: Eugenio Pérez <eperezma@redhat.com>
Reviewed-by: Gal Pressman <redacted>
---
 drivers/vdpa/mlx5/core/mlx5_vdpa.h |  1 +
 drivers/vdpa/mlx5/core/mr.c        | 97 +++++++++++++++++++++---------
 2 files changed, 71 insertions(+), 27 deletions(-)

diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h

b/drivers/vdpa/mlx5/core/mlx5_vdpa.h
index 25fc4120b618..a0420be5059f 100644

--- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h
+++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h

@@ -31,6 +31,7 @@ struct mlx5_vdpa_mr {

        struct list_head head;
        unsigned long num_directs;
        unsigned long num_klms;
+       /* state of dvq mr */
        bool initialized;

        /* serialize mkey creation and destruction */

diff --git a/drivers/vdpa/mlx5/core/mr.c b/drivers/vdpa/mlx5/core/mr.c
index 03e543229791..4ae14a248a4b 100644
--- a/drivers/vdpa/mlx5/core/mr.c
+++ b/drivers/vdpa/mlx5/core/mr.c

@@ -489,60 +489,103 @@ static void destroy_user_mr(struct mlx5_vdpa_dev

*mvdev, struct mlx5_vdpa_mr *mr
        }
 }

-void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev)
+static void _mlx5_vdpa_destroy_cvq_mr(struct mlx5_vdpa_dev *mvdev,
unsigned
int asid)
+{
+       if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] != asid)
+               return;
+
+       prune_iotlb(mvdev);
+}
+
+static void _mlx5_vdpa_destroy_dvq_mr(struct mlx5_vdpa_dev *mvdev,
unsigned
int asid)
 {
        struct mlx5_vdpa_mr *mr = &mvdev->mr;

-       mutex_lock(&mr->mkey_mtx);
+       if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] != asid)
+               return;
+
        if (!mr->initialized)
-               goto out;
+               return;

-       prune_iotlb(mvdev);
        if (mr->user_mr)
                destroy_user_mr(mvdev, mr);
        else
                destroy_dma_mr(mvdev, mr);

        mr->initialized = false;
-out:
+}
+
+static void mlx5_vdpa_destroy_mr_asid(struct mlx5_vdpa_dev *mvdev,
unsigned
int asid)
+{
+       struct mlx5_vdpa_mr *mr = &mvdev->mr;
+
+       mutex_lock(&mr->mkey_mtx);
+
+       _mlx5_vdpa_destroy_dvq_mr(mvdev, asid);
+       _mlx5_vdpa_destroy_cvq_mr(mvdev, asid);
+
        mutex_unlock(&mr->mkey_mtx);
 }

-static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev,
-                               struct vhost_iotlb *iotlb, unsigned int
asid)
+void mlx5_vdpa_destroy_mr(struct mlx5_vdpa_dev *mvdev)
+{
+       mlx5_vdpa_destroy_mr_asid(mvdev, mvdev-

quoted

group2asid[MLX5_VDPA_CVQ_GROUP]);

+       mlx5_vdpa_destroy_mr_asid(mvdev, mvdev-

quoted

group2asid[MLX5_VDPA_DATAVQ_GROUP]);

+}
+
+static int _mlx5_vdpa_create_cvq_mr(struct mlx5_vdpa_dev *mvdev,
+                                   struct vhost_iotlb *iotlb,
+                                   unsigned int asid)
+{
+       if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] != asid)
+               return 0;
+
+       return dup_iotlb(mvdev, iotlb);

This worries me as conceptually, there should be no difference between
dvq mr and cvq mr. The virtqueue should be loosely coupled with mr.

Are you worried by the changes in this patch or about the possibility of
having

The reason for this change is that I noticed if you create one mr in one
asid
you could be blocked out from creating another one in a different asid due
to
mr->initialized being true. To me that seemed problematic. Is it not?

My feeling is that mr.c should be device agnostic. It needs to know
nothing about the device details to work. But this patch seems to
break the layer.

But the same logic was there before (with the exception of cvq not having an
init flag anymore). So what am I missing here?

quoted

quoted

One example is that, if we only do dup_iotlb() but not try to create
dma mr here, we will break virtio-vdpa:

How will that be possible? _mlx5_vdpa_create_mr calls
_mlx5_vdpa_create_dvq_mr
and _mlx5_vdpa_create_cvq_mr. The only thing that is different in this patch
is
that the cvq is not protected by an init flag. My understanding was that it
would be ok to dup_iotlb again. Is it not? If not I could add an additional
initialized flag for the cvq mr.

You are right here.

Thanks

quoted

Thanks,
Dragos

quoted

commit 6f5312f801836e6af9bcbb0bdb44dc423e129206
Author: Eli Cohen [off-list ref]
Date:   Wed Jun 2 11:58:54 2021 +0300

    vdpa/mlx5: Add support for running with virtio_vdpa

    In order to support running vdpa using vritio_vdpa driver, we need  to
    create a different kind of MR, one that has 1:1 mapping, since the
    addresses referring to virtqueues are dma addresses.

    We create the 1:1 MR in mlx5_vdpa_dev_add() only in case firmware
    supports the general capability umem_uid_0. The reason for that is
that
    1:1 MRs must be created with uid == 0 while virtqueue objects can be
    created with uid == 0 only when the firmware capability is on.

    If the set_map() callback is called with new translations provided
    through iotlb, the driver will destroy the 1:1 MR and create a regular
    one.

    Signed-off-by: Eli Cohen [off-list ref]
    Link: https://lore.kernel.org/r/20210602085854.62690-1-elic@nvidia.com (local)
    Signed-off-by: Michael S. Tsirkin [off-list ref]
    Acked-by: Jason Wang [off-list ref]

quoted

Thanks

quoted

quoted

+}
+
+static int _mlx5_vdpa_create_dvq_mr(struct mlx5_vdpa_dev *mvdev,
+                                   struct vhost_iotlb *iotlb,
+                                   unsigned int asid)
 {
        struct mlx5_vdpa_mr *mr = &mvdev->mr;
        int err;

-       if (mr->initialized)
+       if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] != asid)
                return 0;

-       if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid) {
-               if (iotlb)
-                       err = create_user_mr(mvdev, iotlb);
-               else
-                       err = create_dma_mr(mvdev, mr);
+       if (mr->initialized)
+               return 0;

-               if (err)
-                       return err;
-       }
+       if (iotlb)
+               err = create_user_mr(mvdev, iotlb);
+       else
+               err = create_dma_mr(mvdev, mr);

-       if (mvdev->group2asid[MLX5_VDPA_CVQ_GROUP] == asid) {
-               err = dup_iotlb(mvdev, iotlb);
-               if (err)
-                       goto out_err;
-       }
+       if (err)
+               return err;

        mr->initialized = true;
+
+       return 0;
+}
+
+static int _mlx5_vdpa_create_mr(struct mlx5_vdpa_dev *mvdev,
+                               struct vhost_iotlb *iotlb, unsigned int
asid)
+{
+       int err;
+
+       err = _mlx5_vdpa_create_dvq_mr(mvdev, iotlb, asid);
+       if (err)
+               return err;
+
+       err = _mlx5_vdpa_create_cvq_mr(mvdev, iotlb, asid);
+       if (err)
+               goto out_err;
+
        return 0;

 out_err:
-       if (mvdev->group2asid[MLX5_VDPA_DATAVQ_GROUP] == asid) {
-               if (iotlb)
-                       destroy_user_mr(mvdev, mr);
-               else
-                       destroy_dma_mr(mvdev, mr);
-       }
+       _mlx5_vdpa_destroy_dvq_mr(mvdev, asid);

        return err;
 }
--
2.41.0

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