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Date:   Thu, 15 Apr 2021 15:35:31 -0600
From:   Alex Williamson <alex.williamson@redhat.com>
To:     Longfang Liu <liulongfang@huawei.com>
Cc:     <cohuck@redhat.com>, <linux-kernel@vger.kernel.org>,
        <linuxarm@openeuler.org>, Tarun Gupta <targupta@nvidia.com>,
        Neo Jia <cjia@nvidia.com>, Max Gurtovoy <mgurtovoy@nvidia.com>,
        Jason Gunthorpe <jgg@nvidia.com>
Subject: Re: [RFC PATCH 0/3] vfio/hisilicon: add acc live migration driver
Message-ID: <20210415153531.56f6cdf2@redhat.com>
In-Reply-To: <1618284983-55581-1-git-send-email-liulongfang@huawei.com>
References: <1618284983-55581-1-git-send-email-liulongfang@huawei.com>
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[Cc+ NVIDIA folks both from migration and vfio-pci-core discussion]

On Tue, 13 Apr 2021 11:36:20 +0800
Longfang Liu <liulongfang@huawei.com> wrote:

> The live migration solution relies on the vfio_device_migration_info protocol.
> The structure vfio_device_migration_info is placed at the 0th offset of
> the VFIO_REGION_SUBTYPE_MIGRATION region to get and set VFIO device related
> migration information. Field accesses from this structure are only supported
> at their native width and alignment. Otherwise, the result is undefined and
> vendor drivers should return an error.
> 
> (1).The driver framework is based on vfio_pci_register_dev_region() of vfio-pci,
> and then a new live migration region is added, and the live migration is
> realized through the ops of this region.
> 
> (2).In order to ensure the compatibility of the devices before and after the
> migration, the device compatibility information check will be performed in
> the Pre-copy stage. If the check fails, an error will be returned and the
> source VM will exit the migration function.
> 
> (3).After the compatibility check is passed, it will enter the Stop-and-copy
> stage. At this time, all the live migration data will be copied, and then
> saved to the VF device of the destination, and then the VF device of the
> destination will be started and the VM of the source will be exited.
> 
> Longfang Liu (3):
>   vfio/hisilicon: add acc live migration driver
>   vfio/hisilicon: register the driver to vfio
>   vfio/hisilicom: add debugfs for driver
> 
>  drivers/vfio/pci/Kconfig                      |    8 +
>  drivers/vfio/pci/Makefile                     |    1 +
>  drivers/vfio/pci/hisilicon/acc_vf_migration.c | 1337 +++++++++++++++++++++++++
>  drivers/vfio/pci/hisilicon/acc_vf_migration.h |  170 ++++
>  drivers/vfio/pci/vfio_pci.c                   |   11 +
>  drivers/vfio/pci/vfio_pci_private.h           |    9 +
>  6 files changed, 1536 insertions(+)
>  create mode 100644 drivers/vfio/pci/hisilicon/acc_vf_migration.c
>  create mode 100644 drivers/vfio/pci/hisilicon/acc_vf_migration.h
>