From: Cornelia Huck <cohuck@redhat.com>
To: Alex Williamson <alex.williamson@redhat.com>,
Jason Gunthorpe <jgg@nvidia.com>
Cc: Yishai Hadas <yishaih@nvidia.com>,
bhelgaas@google.com, saeedm@nvidia.com,
linux-pci@vger.kernel.org, kvm@vger.kernel.org,
netdev@vger.kernel.org, kuba@kernel.org, leonro@nvidia.com,
kwankhede@nvidia.com, mgurtovoy@nvidia.com, maorg@nvidia.com,
ashok.raj@intel.com, kevin.tian@intel.com,
shameerali.kolothum.thodi@huawei.com
Subject: Re: [PATCH V9 mlx5-next 10/15] vfio: Extend the device migration protocol with RUNNING_P2P
Date: Thu, 24 Feb 2022 17:53:59 +0100 [thread overview]
Message-ID: <87czjc6w9k.fsf@redhat.com> (raw)
In-Reply-To: <20220224093542.3730bb24.alex.williamson@redhat.com>
On Thu, Feb 24 2022, Alex Williamson <alex.williamson@redhat.com> wrote:
> On Thu, 24 Feb 2022 12:13:30 -0400
> Jason Gunthorpe <jgg@nvidia.com> wrote:
>
>> On Thu, Feb 24, 2022 at 08:30:42AM -0700, Alex Williamson wrote:
>> > On Thu, 24 Feb 2022 16:21:11 +0100
>> > Cornelia Huck <cohuck@redhat.com> wrote:
>> > > conflicts with it. We should not create the impression that STOP_COPY
>> > > will neccessarily be mandatory for all time.
>>
>> We really *should* create that impression because a userspace that
>> does not test STOP_COPY in the cases required above is *broken* and
>> must be strongly discouraged from existing.
Well yes, you need STOP_COPY with the current implementation. I'm not
arguing against that.
>>
>> The purpose of this comment is to inform the userspace implementator,
>> not to muse about possible future expansion options for kernel
>> developers. We all agree this expansion path exists and is valid, we
>> need to keep that option open by helping userspace implement
>> correctly.
>
> Chatting with Connie offline, I think the clarification that might help
> is something alone the lines that the combination of bits must support
> migration, which currently requires the STOP_COPY and RESUMING states.
> The VFIO_MIGRATION_P2P flag alone does not provide these states. The
> only flag in the current specification to provide these states is
> VFIO_MIGRATION_STOP_COPY. I don't think we want to preclude that some
> future flag might provide variants of STOP_COPY and RESUMING, so it's
> not so much that VFIO_MIGRATION_STOP_COPY is mandatory, but it is
> currently the only flag which provides the base degree of migration
> support.
Indeed.
>
> How or if that translates to an actual documentation update, I'm not
> sure. As it stands, we're not speculating about future support, we're
> only stating these two combinations are valid. Future combinations may
> or may not include VFIO_MIGRATION_STOP_COPY. As the existing proposed
> comment indicates, other combinations are TBD. Connie? Thanks,
>
> Alex
Hm... "a flag indicating support for a migration state machine such as
VFIO_MIGRATION_STOP_COPY is mandatory"?
next prev parent reply other threads:[~2022-02-24 16:54 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-24 14:20 [PATCH V9 mlx5-next 00/15] Add mlx5 live migration driver and v2 migration protocol Yishai Hadas
2022-02-24 14:20 ` [PATCH V9 mlx5-next 01/15] PCI/IOV: Add pci_iov_vf_id() to get VF index Yishai Hadas
2022-02-24 14:20 ` [PATCH V9 mlx5-next 02/15] net/mlx5: Reuse exported virtfn index function call Yishai Hadas
2022-02-24 14:20 ` [PATCH V9 mlx5-next 03/15] net/mlx5: Disable SRIOV before PF removal Yishai Hadas
2022-02-24 14:20 ` [PATCH V9 mlx5-next 04/15] PCI/IOV: Add pci_iov_get_pf_drvdata() to allow VF reaching the drvdata of a PF Yishai Hadas
2022-02-24 14:20 ` [PATCH V9 mlx5-next 05/15] net/mlx5: Expose APIs to get/put the mlx5 core device Yishai Hadas
2022-02-24 14:20 ` [PATCH V9 mlx5-next 06/15] net/mlx5: Introduce migration bits and structures Yishai Hadas
2022-02-24 14:20 ` [PATCH V9 mlx5-next 07/15] net/mlx5: Add migration commands definitions Yishai Hadas
2022-02-24 14:20 ` [PATCH V9 mlx5-next 08/15] vfio: Have the core code decode the VFIO_DEVICE_FEATURE ioctl Yishai Hadas
2022-03-02 10:00 ` Cornelia Huck
2022-03-02 14:23 ` Jason Gunthorpe
2022-02-24 14:20 ` [PATCH V9 mlx5-next 09/15] vfio: Define device migration protocol v2 Yishai Hadas
2022-03-02 11:19 ` Cornelia Huck
2022-03-02 14:27 ` Jason Gunthorpe
2022-03-02 15:34 ` Alex Williamson
2022-03-02 16:07 ` Cornelia Huck
2022-03-02 16:34 ` Alex Williamson
2022-03-02 16:56 ` Cornelia Huck
2022-03-02 16:34 ` Jason Gunthorpe
2022-03-02 16:57 ` Cornelia Huck
2022-02-24 14:20 ` [PATCH V9 mlx5-next 10/15] vfio: Extend the device migration protocol with RUNNING_P2P Yishai Hadas
2022-02-24 15:21 ` Cornelia Huck
2022-02-24 15:30 ` Alex Williamson
2022-02-24 16:13 ` Jason Gunthorpe
2022-02-24 16:35 ` Alex Williamson
2022-02-24 16:53 ` Cornelia Huck [this message]
2022-02-24 20:46 ` Alex Williamson
2022-03-02 11:51 ` Cornelia Huck
2022-02-24 14:20 ` [PATCH V9 mlx5-next 11/15] vfio: Remove migration protocol v1 documentation Yishai Hadas
2022-03-02 10:09 ` Cornelia Huck
2022-02-24 14:20 ` [PATCH V9 mlx5-next 12/15] vfio/mlx5: Expose migration commands over mlx5 device Yishai Hadas
2022-02-24 14:20 ` [PATCH V9 mlx5-next 13/15] vfio/mlx5: Implement vfio_pci driver for mlx5 devices Yishai Hadas
2022-02-24 14:20 ` [PATCH V9 mlx5-next 14/15] vfio/pci: Expose vfio_pci_core_aer_err_detected() Yishai Hadas
2022-02-24 14:20 ` [PATCH V9 mlx5-next 15/15] vfio/mlx5: Use its own PCI reset_done error handler Yishai Hadas
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