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From: "Mika Penttilä" <mika.penttila@nextfour.com>
To: Jason Wang <jasowang@redhat.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 06:27:02 +0300	[thread overview]
Message-ID: <a77efb06-b2ae-c94a-96bc-290b8b7332ba@nextfour.com> (raw)
In-Reply-To: <e1885255-34f2-9e90-6478-ff0850a5a3d4@redhat.com>



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;
>>   }
>


  reply	other threads:[~2021-04-22  3:27 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 [this message]
2021-04-22  4:52     ` Jason Wang
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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