? 2021/4/22 ??11:27, Mika Penttil? ??:>
>
> On 22.4.2021 5.37, Jason Wang wrote:
>>
>> ? 2021/4/21 ??6:41, Eli Cohen ??:
>>> 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 at 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 at nongnu.org/msg798935.html
[2]
https://lore.kernel.org/virtualization/20210415073147.19331-5-jasowang at
redhat.com/T/
>
> --Mika
>
>
>
>>
>>> ????? return ret;
>>> ? }
>>
>