Messages in this thread | | | Subject | Re: [PATCH] vdpa/mlx5: Add support for doorbell bypassing | From | Jason Wang <> | Date | Thu, 22 Apr 2021 12:52:09 +0800 |
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在 2021/4/22 上午11:27, Mika Penttilä 写道: > > > On 22.4.2021 5.37, Jason Wang wrote: >> >> 在 2021/4/21 下午6:41, Eli Cohen 写道: >>> Implement mlx5_get_vq_notification() to return the doorbell address. >>> Size is set to one system page as required. >>> >>> Signed-off-by: Eli Cohen <elic@nvidia.com> >>> --- >>> drivers/vdpa/mlx5/core/mlx5_vdpa.h | 1 + >>> drivers/vdpa/mlx5/core/resources.c | 1 + >>> drivers/vdpa/mlx5/net/mlx5_vnet.c | 6 ++++++ >>> 3 files changed, 8 insertions(+) >>> >>> diff --git a/drivers/vdpa/mlx5/core/mlx5_vdpa.h >>> b/drivers/vdpa/mlx5/core/mlx5_vdpa.h >>> index b6cc53ba980c..49de62cda598 100644 >>> --- a/drivers/vdpa/mlx5/core/mlx5_vdpa.h >>> +++ b/drivers/vdpa/mlx5/core/mlx5_vdpa.h >>> @@ -41,6 +41,7 @@ struct mlx5_vdpa_resources { >>> u32 pdn; >>> struct mlx5_uars_page *uar; >>> void __iomem *kick_addr; >>> + u64 phys_kick_addr; >>> u16 uid; >>> u32 null_mkey; >>> bool valid; >>> diff --git a/drivers/vdpa/mlx5/core/resources.c >>> b/drivers/vdpa/mlx5/core/resources.c >>> index 6521cbd0f5c2..665f8fc1710f 100644 >>> --- a/drivers/vdpa/mlx5/core/resources.c >>> +++ b/drivers/vdpa/mlx5/core/resources.c >>> @@ -247,6 +247,7 @@ int mlx5_vdpa_alloc_resources(struct >>> mlx5_vdpa_dev *mvdev) >>> goto err_key; >>> kick_addr = mdev->bar_addr + offset; >>> + res->phys_kick_addr = kick_addr; >>> res->kick_addr = ioremap(kick_addr, PAGE_SIZE); >>> if (!res->kick_addr) { >>> diff --git a/drivers/vdpa/mlx5/net/mlx5_vnet.c >>> b/drivers/vdpa/mlx5/net/mlx5_vnet.c >>> index 10c5fef3c020..680751074d2a 100644 >>> --- a/drivers/vdpa/mlx5/net/mlx5_vnet.c >>> +++ b/drivers/vdpa/mlx5/net/mlx5_vnet.c >>> @@ -1865,8 +1865,14 @@ static void mlx5_vdpa_free(struct vdpa_device >>> *vdev) >>> static struct vdpa_notification_area >>> mlx5_get_vq_notification(struct vdpa_device *vdev, u16 idx) >>> { >>> + struct mlx5_vdpa_dev *mvdev = to_mvdev(vdev); >>> struct vdpa_notification_area ret = {}; >>> + struct mlx5_vdpa_net *ndev; >>> + >>> + ndev = to_mlx5_vdpa_ndev(mvdev); >>> + ret.addr = (phys_addr_t)ndev->mvdev.res.phys_kick_addr; >>> + ret.size = PAGE_SIZE; >> >> >> Note that the page will be mapped in to guest, so it's only safe if >> the doorbeel exclusively own the page. This means if there're other >> registers in the page, we can not let the doorbell bypass to work. >> >> So this is suspicious at least in the case of subfunction where we >> calculate the bar length in mlx5_sf_dev_table_create() as: >> >> table->sf_bar_length = 1 << (MLX5_CAP_GEN(dev, log_min_sf_size) + 12); >> >> It looks to me this can only work for the arch with PAGE_SIZE = 4096, >> otherwise we can map more into the userspace(guest). >> >> Thanks >> >> > Is there support as of today (in qemu or elsewhere) to use this mmap > doorbell instead of the traditional kick.
Vhost-user had already had this support in Qemu (see set_host_notifier_mr).
And I've posted patches to support this for qemu[1] and vp_vdpa[2] driver.
Thanks
[1] https://www.mail-archive.com/qemu-devel@nongnu.org/msg798935.html
[2] https://lore.kernel.org/virtualization/20210415073147.19331-5-jasowang@redhat.com/T/
> > --Mika > > > >> >>> return ret; >>> } >> >
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