From: "Tian, Kevin" <kevin.tian@intel.com>
To: Yishai Hadas <yishaih@nvidia.com>,
"alex.williamson@redhat.com" <alex.williamson@redhat.com>,
"bhelgaas@google.com" <bhelgaas@google.com>,
"jgg@nvidia.com" <jgg@nvidia.com>,
"saeedm@nvidia.com" <saeedm@nvidia.com>
Cc: "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"kuba@kernel.org" <kuba@kernel.org>,
"leonro@nvidia.com" <leonro@nvidia.com>,
"kwankhede@nvidia.com" <kwankhede@nvidia.com>,
"mgurtovoy@nvidia.com" <mgurtovoy@nvidia.com>,
"maorg@nvidia.com" <maorg@nvidia.com>,
"Raj, Ashok" <ashok.raj@intel.com>,
"shameerali.kolothum.thodi@huawei.com"
<shameerali.kolothum.thodi@huawei.com>
Subject: RE: [PATCH V7 mlx5-next 08/15] vfio: Define device migration protocol v2
Date: Tue, 15 Feb 2022 08:04:27 +0000 [thread overview]
Message-ID: <BN9PR11MB5276B8754BA82E94CF288F8C8C349@BN9PR11MB5276.namprd11.prod.outlook.com> (raw)
In-Reply-To: <20220207172216.206415-9-yishaih@nvidia.com>
> From: Yishai Hadas <yishaih@nvidia.com>
> Sent: Tuesday, February 8, 2022 1:22 AM
>
> +static int vfio_ioctl_device_feature_migration(struct vfio_device *device,
> + u32 flags, void __user *arg,
> + size_t argsz)
> +{
> + struct vfio_device_feature_migration mig = {
> + .flags = VFIO_MIGRATION_STOP_COPY,
> + };
> + int ret;
> +
> + if (!device->ops->migration_set_state)
> + return -ENOTTY;
Miss a check on migration_get_state, as done in last function.
> + * @migration_set_state: Optional callback to change the migration state for
> + * devices that support migration. The returned FD is used for data
> + * transfer according to the FSM definition. The driver is responsible
> + * to ensure that FD is isolated whenever the migration FSM leaves a
> + * data transfer state or before close_device() returns.
didn't understand the meaning of 'isolated' here.
> +#define VFIO_DEVICE_STATE_V1_STOP (0)
> +#define VFIO_DEVICE_STATE_V1_RUNNING (1 << 0)
> +#define VFIO_DEVICE_STATE_V1_SAVING (1 << 1)
> +#define VFIO_DEVICE_STATE_V1_RESUMING (1 << 2)
> +#define VFIO_DEVICE_STATE_MASK (VFIO_DEVICE_STATE_V1_RUNNING
> | \
> + VFIO_DEVICE_STATE_V1_SAVING | \
> + VFIO_DEVICE_STATE_V1_RESUMING)
Does it make sense to also add 'V1' to MASK and also following macros
given their names are general?
#define VFIO_DEVICE_STATE_VALID(state) \
#define VFIO_DEVICE_STATE_IS_ERROR(state) \
#define VFIO_DEVICE_STATE_SET_ERROR(state) \
It certainly implies more changes to v1 code but readability can be
slightly improved.
> +/*
> + * Indicates the device can support the migration API. See enum
call it V2? Not necessary to add V2 in code but worthy of a clarification
in comment.
> + * vfio_device_mig_state for details. If present flags must be non-zero and
> + * VFIO_DEVICE_FEATURE_MIG_DEVICE_STATE is supported.
> + *
> + * VFIO_MIGRATION_STOP_COPY means that RUNNING, STOP, STOP_COPY
> and
> + * RESUMING are supported.
> + */
Not aligned with other places where 5 states are mentioned. Better add
ERROR here.
> + *
> + * RUNNING -> STOP
> + * STOP_COPY -> STOP
> + * While in STOP the device must stop the operation of the device. The
> + * device must not generate interrupts, DMA, or advance its internal
> + * state. When stopped the device and kernel migration driver must accept
> + * and respond to interaction to support external subsystems in the STOP
> + * state, for example PCI MSI-X and PCI config pace. Failure by the user to
> + * restrict device access while in STOP must not result in error conditions
> + * outside the user context (ex. host system faults).
Right above the STOP state is defined as:
* STOP - The device does not change the internal or external state
'external state' I assume means P2P activities. For consistency it is clearer
to also say something about external state in above paragraph.
> + *
> + * The STOP_COPY arc will terminate a data transfer session.
remove 'will'
> + *
> + * STOP -> STOP_COPY
> + * This arc begin the process of saving the device state and will return a
> + * new data_fd.
> + *
> + * While in the STOP_COPY state the device has the same behavior as STOP
> + * with the addition that the data transfers session continues to stream the
> + * migration state. End of stream on the FD indicates the entire device
> + * state has been transferred.
> + *
> + * The user should take steps to restrict access to vfio device regions while
> + * the device is in STOP_COPY or risk corruption of the device migration
> data
> + * stream.
Restricting access has been explained in the to-STOP arcs and it is stated
that while in STOP_COPY the device has the same behavior as STOP. So
I think the last paragraph is possibly not required.
> + *
> + * STOP -> RESUMING
> + * Entering the RESUMING state starts a process of restoring the device
> + * state and will return a new data_fd. The data stream fed into the
> data_fd
> + * should be taken from the data transfer output of the saving group states
No definition of 'group state' (maybe introduced in a later patch?)
> + * from a compatible device. The migration driver may alter/reset the
> + * internal device state for this arc if required to prepare the device to
> + * receive the migration data.
> + *
Thanks
Kevin
next prev parent reply other threads:[~2022-02-15 8:04 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-07 17:22 [PATCH V7 mlx5-next 00/15] Add mlx5 live migration driver and v2 migration protocol Yishai Hadas
2022-02-07 17:22 ` [PATCH V7 mlx5-next 01/15] PCI/IOV: Add pci_iov_vf_id() to get VF index Yishai Hadas
2022-02-07 17:22 ` [PATCH V7 mlx5-next 02/15] net/mlx5: Reuse exported virtfn index function call Yishai Hadas
2022-02-07 17:22 ` [PATCH V7 mlx5-next 03/15] net/mlx5: Disable SRIOV before PF removal Yishai Hadas
2022-02-07 17:22 ` [PATCH V7 mlx5-next 04/15] PCI/IOV: Add pci_iov_get_pf_drvdata() to allow VF reaching the drvdata of a PF Yishai Hadas
2022-02-07 17:22 ` [PATCH V7 mlx5-next 05/15] net/mlx5: Expose APIs to get/put the mlx5 core device Yishai Hadas
2022-02-07 17:22 ` [PATCH V7 mlx5-next 06/15] net/mlx5: Introduce migration bits and structures Yishai Hadas
2022-02-07 17:22 ` [PATCH V7 mlx5-next 07/15] vfio: Have the core code decode the VFIO_DEVICE_FEATURE ioctl Yishai Hadas
2022-02-07 17:22 ` [PATCH V7 mlx5-next 08/15] vfio: Define device migration protocol v2 Yishai Hadas
2022-02-09 0:07 ` Alex Williamson
2022-02-09 2:36 ` Jason Gunthorpe
2022-02-15 10:41 ` Tian, Kevin
2022-02-15 16:04 ` Jason Gunthorpe
2022-02-15 23:32 ` Alex Williamson
2022-02-16 1:17 ` Jason Gunthorpe
2022-02-16 3:17 ` Tian, Kevin
2022-02-16 12:14 ` Jason Gunthorpe
2022-02-17 2:29 ` Tian, Kevin
2022-02-15 10:58 ` Tian, Kevin
2022-02-15 13:13 ` Jason Gunthorpe
2022-02-15 8:04 ` Tian, Kevin [this message]
2022-02-15 15:33 ` Jason Gunthorpe
2022-02-16 3:04 ` Tian, Kevin
2022-02-07 17:22 ` [PATCH V7 mlx5-next 09/15] vfio: Extend the device migration protocol with RUNNING_P2P Yishai Hadas
2022-02-15 10:18 ` Tian, Kevin
2022-02-15 15:56 ` Jason Gunthorpe
2022-02-16 2:52 ` Tian, Kevin
2022-02-16 12:11 ` Jason Gunthorpe
2022-02-07 17:22 ` [PATCH V7 mlx5-next 10/15] vfio: Remove migration protocol v1 documentation Yishai Hadas
2022-02-11 11:03 ` Cornelia Huck
2022-02-07 17:22 ` [PATCH V7 mlx5-next 11/15] vfio/mlx5: Expose migration commands over mlx5 device Yishai Hadas
2022-02-07 17:22 ` [PATCH V7 mlx5-next 12/15] vfio/mlx5: Implement vfio_pci driver for mlx5 devices Yishai Hadas
2022-02-09 0:07 ` Alex Williamson
2022-02-07 17:22 ` [PATCH V7 mlx5-next 13/15] vfio/pci: Expose vfio_pci_core_aer_err_detected() Yishai Hadas
2022-02-07 17:22 ` [PATCH V7 mlx5-next 14/15] vfio/mlx5: Use its own PCI reset_done error handler Yishai Hadas
2022-02-09 0:08 ` Alex Williamson
2022-02-09 2:39 ` Jason Gunthorpe
2022-02-10 16:48 ` Alex Williamson
2022-02-10 17:27 ` Jason Gunthorpe
2022-02-07 17:22 ` [PATCH V7 mlx5-next 15/15] vfio: Extend the device migration protocol with PRE_COPY Yishai Hadas
2022-02-17 17:15 ` Alex Williamson
2022-02-18 0:03 ` Jason Gunthorpe
2022-02-18 8:01 ` Tian, Kevin
2022-02-18 14:06 ` Jason Gunthorpe
2022-02-22 1:43 ` Tian, Kevin
2022-02-22 15:50 ` Jason Gunthorpe
2022-02-23 0:40 ` Tian, Kevin
2022-02-23 0:44 ` Jason Gunthorpe
2022-02-23 1:46 ` Tian, Kevin
2022-02-18 8:11 ` [PATCH V7 mlx5-next 00/15] Add mlx5 live migration driver and v2 migration protocol Tarun Gupta (SW-GPU)
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