Messages in this thread | | | Subject | Re: [PATCH] vdpa/mlx5: Add support for doorbell bypassing | From | Mika Penttilä <> | Date | Thu, 22 Apr 2021 06:27:02 +0300 |
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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.
--Mika
> >> return ret; >> } >
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