From: Alex Williamson <alex.williamson@redhat.com>
To: Max Gurtovoy <mgurtovoy@nvidia.com>
Cc: Jason Gunthorpe <jgg@ziepe.ca>, Leon Romanovsky <leon@kernel.org>,
Doug Ledford <dledford@redhat.com>,
Yishai Hadas <yishaih@nvidia.com>,
Bjorn Helgaas <bhelgaas@google.com>,
"David S. Miller" <davem@davemloft.net>,
Jakub Kicinski <kuba@kernel.org>,
Kirti Wankhede <kwankhede@nvidia.com>, <kvm@vger.kernel.org>,
<linux-kernel@vger.kernel.org>, <linux-pci@vger.kernel.org>,
<linux-rdma@vger.kernel.org>, <netdev@vger.kernel.org>,
Saeed Mahameed <saeedm@nvidia.com>,
Cornelia Huck <cohuck@redhat.com>
Subject: Re: [PATCH mlx5-next 2/7] vfio: Add an API to check migration state transition validity
Date: Wed, 29 Sep 2021 06:35:51 -0600 [thread overview]
Message-ID: <20210929063551.47590fbb.alex.williamson@redhat.com> (raw)
In-Reply-To: <25c97be6-eb4a-fdc8-3ac1-5628073f0214@nvidia.com>
On Wed, 29 Sep 2021 13:44:10 +0300
Max Gurtovoy <mgurtovoy@nvidia.com> wrote:
> On 9/28/2021 2:12 AM, Jason Gunthorpe wrote:
> > On Mon, Sep 27, 2021 at 04:46:48PM -0600, Alex Williamson wrote:
> >>> + enum { MAX_STATE = VFIO_DEVICE_STATE_RESUMING };
> >>> + static const u8 vfio_from_state_table[MAX_STATE + 1][MAX_STATE + 1] = {
> >>> + [VFIO_DEVICE_STATE_STOP] = {
> >>> + [VFIO_DEVICE_STATE_RUNNING] = 1,
> >>> + [VFIO_DEVICE_STATE_RESUMING] = 1,
> >>> + },
> >> Our state transition diagram is pretty weak on reachable transitions
> >> out of the _STOP state, why do we select only these two as valid?
> > I have no particular opinion on specific states here, however adding
> > more states means more stuff for drivers to implement and more risk
> > driver writers will mess up this uAPI.
>
> _STOP == 000b => Device Stopped, not saving or resuming (from UAPI).
>
> This is the default initial state and not RUNNING.
>
> The user application should move device from STOP => RUNNING or STOP =>
> RESUMING.
>
> Maybe we need to extend the comment in the UAPI file.
include/uapi/linux/vfio.h:
...
* +------- _RESUMING
* |+------ _SAVING
* ||+----- _RUNNING
* |||
* 000b => Device Stopped, not saving or resuming
* 001b => Device running, which is the default state
^^^^^^^^^^^^^^^^^^^^^^^^^^
...
* State transitions:
*
* _RESUMING _RUNNING Pre-copy Stop-and-copy _STOP
* (100b) (001b) (011b) (010b) (000b)
* 0. Running or default state
* |
^^^^^^^^^^^^^
...
* 0. Default state of VFIO device is _RUNNING when the user application starts.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
The uAPI is pretty clear here. A default state of _STOP is not
compatible with existing devices and userspace that does not support
migration. Thanks,
Alex
next prev parent reply other threads:[~2021-09-29 12:35 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-22 10:38 [PATCH mlx5-next 0/7] Add mlx5 live migration driver Leon Romanovsky
2021-09-22 10:38 ` [PATCH mlx5-next 1/7] PCI/IOV: Provide internal VF index Leon Romanovsky
2021-09-22 21:59 ` Bjorn Helgaas
2021-09-23 6:35 ` Leon Romanovsky
2021-09-24 13:08 ` Bjorn Helgaas
2021-09-25 10:10 ` Leon Romanovsky
2021-09-25 17:41 ` Bjorn Helgaas
2021-09-26 6:36 ` Leon Romanovsky
2021-09-26 20:23 ` Bjorn Helgaas
2021-09-27 11:55 ` Leon Romanovsky
2021-09-27 14:47 ` Bjorn Helgaas
2021-09-22 10:38 ` [PATCH mlx5-next 2/7] vfio: Add an API to check migration state transition validity Leon Romanovsky
2021-09-23 10:33 ` Shameerali Kolothum Thodi
2021-09-23 11:17 ` Leon Romanovsky
2021-09-23 13:55 ` Max Gurtovoy
2021-09-24 7:44 ` Shameerali Kolothum Thodi
2021-09-24 9:37 ` Kirti Wankhede
2021-09-26 9:09 ` Max Gurtovoy
2021-09-26 16:17 ` Shameerali Kolothum Thodi
2021-09-27 18:24 ` Max Gurtovoy
2021-09-27 18:29 ` Shameerali Kolothum Thodi
2021-09-27 22:46 ` Alex Williamson
2021-09-27 23:12 ` Jason Gunthorpe
2021-09-28 19:19 ` Alex Williamson
2021-09-28 19:35 ` Jason Gunthorpe
2021-09-28 20:18 ` Alex Williamson
2021-09-29 16:16 ` Jason Gunthorpe
2021-09-29 18:06 ` Alex Williamson
2021-09-29 18:26 ` Jason Gunthorpe
2021-09-29 10:57 ` Max Gurtovoy
2021-09-29 10:44 ` Max Gurtovoy
2021-09-29 12:35 ` Alex Williamson [this message]
2021-09-29 13:26 ` Max Gurtovoy
2021-09-29 13:50 ` Alex Williamson
2021-09-29 14:36 ` Max Gurtovoy
2021-09-29 15:17 ` Alex Williamson
2021-09-29 15:28 ` Max Gurtovoy
2021-09-29 16:14 ` Jason Gunthorpe
2021-09-29 21:48 ` Max Gurtovoy
2021-09-29 22:44 ` Alex Williamson
2021-09-30 9:25 ` Max Gurtovoy
2021-09-30 12:41 ` Alex Williamson
2021-09-29 23:21 ` Jason Gunthorpe
2021-09-30 9:34 ` Max Gurtovoy
2021-09-30 14:47 ` Jason Gunthorpe
2021-09-30 15:32 ` Max Gurtovoy
2021-09-30 16:24 ` Jason Gunthorpe
2021-09-30 16:51 ` Max Gurtovoy
2021-09-30 17:01 ` Jason Gunthorpe
2021-09-22 10:38 ` [PATCH mlx5-next 3/7] vfio/pci_core: Make the region->release() function optional Leon Romanovsky
2021-09-23 13:57 ` Max Gurtovoy
2021-09-22 10:38 ` [PATCH mlx5-next 4/7] net/mlx5: Introduce migration bits and structures Leon Romanovsky
2021-09-24 5:48 ` Mark Zhang
2021-09-22 10:38 ` [PATCH mlx5-next 5/7] net/mlx5: Expose APIs to get/put the mlx5 core device Leon Romanovsky
2021-09-22 10:38 ` [PATCH mlx5-next 6/7] mlx5_vfio_pci: Expose migration commands over mlx5 device Leon Romanovsky
2021-09-28 20:22 ` Alex Williamson
2021-09-29 5:36 ` Leon Romanovsky
2021-09-22 10:38 ` [PATCH mlx5-next 7/7] mlx5_vfio_pci: Implement vfio_pci driver for mlx5 devices Leon Romanovsky
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