On Wed, Aug 9, 2023 at 6:58 AM Si-Wei Liu <si-wei.liu@xxxxxxxxxx> wrote:
>
>
>
> On 8/7/2023 8:00 PM, Jason Wang wrote:
> > On Fri, Aug 4, 2023 at 1:58 AM Si-Wei Liu <si-wei.liu@xxxxxxxxxx> wrote:
> >>
> >>
> >> On 8/3/2023 1:03 AM, Jason Wang wrote:
> >>> On Thu, Aug 3, 2023 at 1:13 AM Dragos Tatulea <dtatulea@xxxxxxxxxx> wrote:
> >>>> 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@xxxxxxxxxx>
> >>>> Reviewed-by: Eugenio Pérez <eperezma@xxxxxxxxxx>
> >>>> Reviewed-by: Gal Pressman <gal@xxxxxxxxxx>
> >>>> ---
> >>>> 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->group2asid[MLX5_VDPA_CVQ_GROUP]);
> >>>> + mlx5_vdpa_destroy_mr_asid(mvdev, mvdev->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.
> >>>
> >>> One example is that, if we only do dup_iotlb() but not try to create
> >>> dma mr here, we will break virtio-vdpa:
> >> For this case, I guess we may need another way to support virtio-vdpa
> >> 1:1 mapping rather than overloading virtio device reset semantics, see:
> >>
> >> https://www.mail-archive.com/qemu-devel@xxxxxxxxxx/msg953755.html
> >>
> >> > Conceptually, the address mapping is not a part of the abstraction for
> >> > a virtio device now. So resetting the memory mapping during virtio
> >> > device reset seems wrong.
> >>
> >> where we want to keep memory mapping intact across virtio device reset
> >> for best live migration latency/downtime. I wonder would it work to
> >> reset the mapping in vhost-vdpa life cycle out of virtio reset, say
> >> introduce a .reset_map() op to restore 1:1 mapping within
> >> vhost_vdpa_remove_as() right after vhost_vdpa_iotlb_unmap()? Then we can
> >> move the iotlb reset logic to there without worry breaking virtio-vdpa.
> > It looks to me we don't need a new ops. We can simply do set_map()
> > twice
> What does it mean, first set_map(0, -1ULL) with zero iotlb entry passed
> in to destroy all iotlb mappings previously added, and second set_map(0,
> -1ULL) to restore 1:1 DMA MR? But userspace (maybe a buggy one but
> doesn't do harm) apart from vhost-vdpa itself can do unmap twice anyway,
> this is supported today I think. Why there'll be such obscure
> distinction, or what's the benefit to treat second .set_map() as
> recreating 1:1 mapping?
Ok, I think I miss some context. I agree that it's better to decouple
memory mappings from the virtio reset. It helps to reduce the
unnecessary memory transactions. It might require a new feature flag.
Regarding the method of restoring to 1:1 DMA MR, it might be dangerous
for (buggy) vhost-vDPA devices. Since its userspace doesn't set up any
mapping it can explore the kernel with that via CVQ?
Thanks
>
> > or do you mean it would be faster?
> I think with .reset_map() we at least can avoid indefinite latency
> hiccup from destroying and recreating 1:1 mapping with the unwarranted
> 2rd unmap call. And .reset_map() should work with both .dma_map() and
> .set_map() APIs with clear semantics.
>
> Regards,
> -Siwei
> >
> > Thanks
> >
> >> Thanks,
> >> -Siwei
> >>
> >>> commit 6f5312f801836e6af9bcbb0bdb44dc423e129206
> >>> Author: Eli Cohen <elic@xxxxxxxxxx>
> >>> 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 <elic@xxxxxxxxxx>
> >>> Link: https://lore.kernel.org/r/20210602085854.62690-1-elic@xxxxxxxxxx
> >>> Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
> >>> Acked-by: Jason Wang <jasowang@xxxxxxxxxx>
> >>>
> >>> Thanks
> >>>
> >>>
> >>>> +}
> >>>> +
> >>>> +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
> >>>>
> >>> _______________________________________________
> >>> Virtualization mailing list
> >>> Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
> >>> https://lists.linuxfoundation.org/mailman/listinfo/virtualization
>
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