From: Alex Williamson <alex.williamson@redhat.com>
To: Jason Gunthorpe <jgg@nvidia.com>
Cc: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>,
Cornelia Huck <cohuck@redhat.com>,
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,
"Dr. David Alan Gilbert" <dgilbert@redhat.com>
Subject: Re: [PATCH V2 mlx5-next 12/14] vfio/mlx5: Implement vfio_pci driver for mlx5 devices
Date: Tue, 2 Nov 2021 10:22:36 -0600 [thread overview]
Message-ID: <20211102102236.711dc6b5.alex.williamson@redhat.com> (raw)
In-Reply-To: <20211102155420.GK2744544@nvidia.com>
On Tue, 2 Nov 2021 12:54:20 -0300
Jason Gunthorpe <jgg@nvidia.com> wrote:
> On Tue, Nov 02, 2021 at 08:56:51AM -0600, Alex Williamson wrote:
>
> > > Still, this is something that needs clear definition, I would expect
> > > the SET_IRQS to happen after resuming clears but before running sets
> > > to give maximum HW flexibility and symmetry with saving.
> >
> > There's no requirement that the device enters a null state (!_RESUMING
> > | !_SAVING | !_RUNNING), the uAPI even species the flows as _RESUMING
> > transitioning to _RUNNING.
>
> If the device saves the MSI-X state inside it's migration data (as
> apparently would be convenient for other OSs) then when RESUMING
> clears and the migration data is de-serialized the device will
> overwrite the MSI-X data.
>
> Since Linux as an OS wants to control the MSI-X it needs to load it
> after RESUMING, but before RUNNING.
This is not how it works today, QEMU enables MSI/X based on the config
space information, which is also outside of the device migration stream.
> > There's no point at which we can do SET_IRQS other than in the
> > _RESUMING state. Generally SET_IRQS ioctls are coordinated with the
> > guest driver based on actions to the device, we can't be mucking
> > with IRQs while the device is presumed running and already
> > generating interrupt conditions.
>
> We need to do it in state 000
>
> ie resume should go
>
> 000 -> 100 -> 000 -> 001
>
> With SET_IRQS and any other fixing done during the 2nd 000, after the
> migration data has been loaded into the device.
Again, this is not how QEMU works today.
> > > And we should really define clearly what a device is supposed to do
> > > with the interrupt vectors during migration. Obviously there are races
> > > here.
> >
> > The device should not be generating interrupts while !_RUNNING, pending
> > interrupts should be held until the device is _RUNNING. To me this
> > means the sequence must be that INTx/MSI/MSI-X are restored while in
> > the !_RUNNING state.
>
> Yes
Except I suppose them to be restored while _RESUMING is set.
> > > > In any case, it requires that the device cannot be absolutely static
> > > > while !_RUNNING. Does (_RESUMING) have different rules than
> > > > (_SAVING)?
> > >
> > > I'd prever to avoid all device touches during both resuming and
> > > saving, and do them during !RUNNING
> >
> > There's no such state required by the uAPI.
>
> The uAPI comment does not define when to do the SET_IRQS, it seems
> this has been missed.
>
> We really should fix it, unless you feel strongly that the
> experimental API in qemu shouldn't be changed.
I think the QEMU implementation fills in some details of how the uAPI
is expected to work. MSI/X is expected to be restored while _RESUMING
based on the config space of the device, there is no intermediate step
between _RESUMING and _RUNNING. Introducing such a requirement
precludes the option of a post-copy implementation of (_RESUMING |
_RUNNING). Thanks,
Alex
next prev parent reply other threads:[~2021-11-02 16:37 UTC|newest]
Thread overview: 100+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-19 10:58 [PATCH V2 mlx5-next 00/14] Add mlx5 live migration driver Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 01/14] PCI/IOV: Add pci_iov_vf_id() to get VF index Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 02/14] net/mlx5: Reuse exported virtfn index function call Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 03/14] net/mlx5: Disable SRIOV before PF removal Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 04/14] PCI/IOV: Add pci_iov_get_pf_drvdata() to allow VF reaching the drvdata of a PF Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 05/14] net/mlx5: Expose APIs to get/put the mlx5 core device Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 06/14] vdpa/mlx5: Use mlx5_vf_get_core_dev() to get PF device Yishai Hadas
2021-10-19 11:16 ` Max Gurtovoy
2021-10-20 8:58 ` Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 07/14] vfio: Fix VFIO_DEVICE_STATE_SET_ERROR macro Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 08/14] vfio: Add a macro for VFIO_DEVICE_STATE_ERROR Yishai Hadas
2021-10-19 15:48 ` Alex Williamson
2021-10-19 15:50 ` Alex Williamson
2021-10-20 7:35 ` Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 09/14] vfio/pci_core: Make the region->release() function optional Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 10/14] net/mlx5: Introduce migration bits and structures Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 11/14] vfio/mlx5: Expose migration commands over mlx5 device Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 12/14] vfio/mlx5: Implement vfio_pci driver for mlx5 devices Yishai Hadas
2021-10-19 18:43 ` Alex Williamson
2021-10-19 19:23 ` Jason Gunthorpe
2021-10-19 20:58 ` Alex Williamson
2021-10-19 23:04 ` Jason Gunthorpe
2021-10-20 8:28 ` Yishai Hadas
2021-10-20 16:52 ` Alex Williamson
2021-10-20 18:59 ` Jason Gunthorpe
2021-10-20 21:07 ` Alex Williamson
2021-10-21 9:34 ` Cornelia Huck
2021-10-21 21:47 ` Alex Williamson
2021-10-25 12:29 ` Jason Gunthorpe
2021-10-25 14:28 ` Alex Williamson
2021-10-25 14:56 ` Jason Gunthorpe
2021-10-26 14:42 ` Alex Williamson
2021-10-26 15:18 ` Jason Gunthorpe
2021-10-26 19:50 ` Alex Williamson
2021-10-26 23:43 ` Jason Gunthorpe
2021-10-27 19:05 ` Alex Williamson
2021-10-27 19:23 ` Jason Gunthorpe
2021-10-28 15:08 ` Cornelia Huck
2021-10-29 0:26 ` Jason Gunthorpe
2021-10-29 7:35 ` Yishai Hadas
2021-10-28 15:30 ` Alex Williamson
2021-10-28 23:47 ` Jason Gunthorpe
2021-10-29 6:57 ` Cornelia Huck
2021-10-29 7:48 ` Yishai Hadas
2021-10-29 10:32 ` Shameerali Kolothum Thodi
2021-10-29 12:15 ` Jason Gunthorpe
2021-10-29 22:06 ` Alex Williamson
2021-11-01 17:25 ` Jason Gunthorpe
2021-11-02 11:19 ` Shameerali Kolothum Thodi
2021-11-02 14:56 ` Alex Williamson
2021-11-02 15:54 ` Jason Gunthorpe
2021-11-02 16:22 ` Alex Williamson [this message]
2021-11-02 16:36 ` Jason Gunthorpe
2021-11-02 20:15 ` Alex Williamson
2021-11-03 12:09 ` Jason Gunthorpe
2021-11-03 15:44 ` Alex Williamson
2021-11-03 16:10 ` Jason Gunthorpe
2021-11-03 18:04 ` Alex Williamson
2021-11-04 11:19 ` Cornelia Huck
2021-11-05 16:53 ` Cornelia Huck
2021-11-16 16:59 ` Cornelia Huck
2021-11-05 13:24 ` Jason Gunthorpe
2021-11-05 15:31 ` Alex Williamson
2021-11-15 23:29 ` Jason Gunthorpe
2021-11-16 17:57 ` Alex Williamson
2021-11-16 19:25 ` Jason Gunthorpe
2021-11-16 21:10 ` Alex Williamson
2021-11-17 1:48 ` Jason Gunthorpe
2021-11-18 18:15 ` Alex Williamson
2021-11-22 19:18 ` Jason Gunthorpe
2021-11-08 8:53 ` Tian, Kevin
2021-11-08 12:35 ` Jason Gunthorpe
2021-11-09 0:58 ` Tian, Kevin
2021-11-09 12:45 ` Jason Gunthorpe
2021-10-25 16:34 ` Dr. David Alan Gilbert
2021-10-25 17:55 ` Alex Williamson
2021-10-25 18:47 ` Dr. David Alan Gilbert
2021-10-25 19:15 ` Jason Gunthorpe
2021-10-26 8:40 ` Dr. David Alan Gilbert
2021-10-26 12:13 ` Jason Gunthorpe
2021-10-26 14:52 ` Alex Williamson
2021-10-26 15:56 ` Jason Gunthorpe
2021-10-26 14:29 ` Alex Williamson
2021-10-26 14:51 ` Dr. David Alan Gilbert
2021-10-26 15:25 ` Jason Gunthorpe
2021-10-20 8:01 ` Yishai Hadas
2021-10-20 16:25 ` Jason Gunthorpe
2021-10-21 10:46 ` Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 13/14] vfio/pci: Expose vfio_pci_aer_err_detected() Yishai Hadas
2021-10-19 10:58 ` [PATCH V2 mlx5-next 14/14] vfio/mlx5: Use its own PCI reset_done error handler Yishai Hadas
2021-10-19 18:55 ` Alex Williamson
2021-10-19 19:10 ` Jason Gunthorpe
2021-10-20 8:46 ` Yishai Hadas
2021-10-20 16:46 ` Jason Gunthorpe
2021-10-20 17:45 ` Alex Williamson
2021-10-20 18:57 ` Jason Gunthorpe
2021-10-20 21:38 ` Alex Williamson
2021-10-21 10:39 ` Yishai Hadas
2021-11-17 16:42 ` vfio migration discussions (was: [PATCH V2 mlx5-next 00/14] Add mlx5 live migration driver) Cornelia Huck
2021-11-17 17:47 ` Jason Gunthorpe
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