netdev - Re: [PATCH V2 vfio 03/11] vfio: Introduce DMA logging uAPIs

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Message-ID: <692a0d74-9ef4-06b7-c9d6-3d88820f5160@nvidia.com>
Date:   Tue, 19 Jul 2022 11:10:04 +0530
From:   Kirti Wankhede <kwankhede@...dia.com>
To:     "Tian, Kevin" <kevin.tian@...el.com>,
        Alex Williamson <alex.williamson@...hat.com>,
        Yishai Hadas <yishaih@...dia.com>
Cc:     "jgg@...dia.com" <jgg@...dia.com>,
        "saeedm@...dia.com" <saeedm@...dia.com>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "Martins, Joao" <joao.m.martins@...cle.com>,
        "leonro@...dia.com" <leonro@...dia.com>,
        "maorg@...dia.com" <maorg@...dia.com>,
        "cohuck@...hat.com" <cohuck@...hat.com>, Neo Jia <cjia@...dia.com>,
        Tarun Gupta <targupta@...dia.com>,
        Shounak Deshpande <shdeshpande@...dia.com>
Subject: Re: [PATCH V2 vfio 03/11] vfio: Introduce DMA logging uAPIs



On 7/19/2022 7:09 AM, Tian, Kevin wrote:
>> From: Alex Williamson <alex.williamson@...hat.com>
>> Sent: Tuesday, July 19, 2022 6:30 AM
>>
>> On Thu, 14 Jul 2022 11:12:43 +0300
>> Yishai Hadas <yishaih@...dia.com> wrote:
>>
>>> DMA logging allows a device to internally record what DMAs the device is
>>> initiating and report them back to userspace. It is part of the VFIO
>>> migration infrastructure that allows implementing dirty page tracking
>>> during the pre copy phase of live migration. Only DMA WRITEs are logged,
>>> and this API is not connected to
>> VFIO_DEVICE_FEATURE_MIG_DEVICE_STATE.
>>>
>>> This patch introduces the DMA logging involved uAPIs.
>>>
>>> It uses the FEATURE ioctl with its GET/SET/PROBE options as of below.
>>>
>>> It exposes a PROBE option to detect if the device supports DMA logging.
>>> It exposes a SET option to start device DMA logging in given IOVAs
>>> ranges.
>>> It exposes a SET option to stop device DMA logging that was previously
>>> started.
>>> It exposes a GET option to read back and clear the device DMA log.
>>>
>>> Extra details exist as part of vfio.h per a specific option.
>>
>>
>> Kevin, Kirti, others, any comments on this uAPI proposal?  Are there
>> potentially other devices that might make use of this or is everyone
>> else waiting for IOMMU based dirty tracking?
>>
> 

I had briefly screened through it, I'm taking a closer look of it.

NVIDIA vGPU might use this API.

Thanks,
Kirti