From: Jason Wang <jasowang@redhat.com>
To: "Mika Penttilä" <mika.penttila@nextfour.com>,
"Eli Cohen" <elic@nvidia.com>,
mst@redhat.com
Cc: virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] vdpa/mlx5: Add support for doorbell bypassing
Date: Thu, 22 Apr 2021 12:52:09 +0800 [thread overview]
Message-ID: <7bdb251a-5e16-dd22-d204-6ff57e12e72f@redhat.com> (raw)
In-Reply-To: <a77efb06-b2ae-c94a-96bc-290b8b7332ba@nextfour.com>
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;
>>> }
>>
>
next prev parent reply other threads:[~2021-04-22 4:52 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-21 10:41 [PATCH] vdpa/mlx5: Add support for doorbell bypassing Eli Cohen
2021-04-22 2:37 ` Jason Wang
2021-04-22 3:27 ` Mika Penttilä
2021-04-22 4:52 ` Jason Wang [this message]
2021-04-22 6:03 ` Eli Cohen
2021-04-22 8:07 ` Eli Cohen
2021-04-22 8:21 ` Jason Wang
2021-04-22 8:39 ` Eli Cohen
2021-04-22 8:59 ` Jason Wang
2021-04-25 13:25 ` Eli Cohen
2021-04-26 2:35 ` Jason Wang
2021-04-28 20:53 ` Si-Wei Liu
2021-04-29 2:43 ` Jason Wang
2021-04-29 10:00 ` Eli Cohen
2021-04-30 4:40 ` Jason Wang
2021-04-30 6:31 ` Zhu, Lingshan
2021-04-30 7:03 ` Jason Wang
2021-04-30 9:25 ` Zhu, Lingshan
2021-04-30 13:49 ` Jason Wang
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