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Date:   Tue, 28 Sep 2021 14:18:44 -0600
From:   Alex Williamson <alex.williamson@redhat.com>
To:     Jason Gunthorpe <jgg@ziepe.ca>
Cc:     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
Message-ID: <20210928141844.15cea787.alex.williamson@redhat.com>
In-Reply-To: <20210928193550.GR3544071@ziepe.ca>
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        <20210927164648.1e2d49ac.alex.williamson@redhat.com>
        <20210927231239.GE3544071@ziepe.ca>
        <20210928131958.61b3abec.alex.williamson@redhat.com>
        <20210928193550.GR3544071@ziepe.ca>
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On Tue, 28 Sep 2021 16:35:50 -0300
Jason Gunthorpe <jgg@ziepe.ca> wrote:

> On Tue, Sep 28, 2021 at 01:19:58PM -0600, Alex Williamson wrote:
> 
> > In defining the device state, we tried to steer away from defining it
> > in terms of the QEMU migration API, but rather as a set of controls
> > that could be used to support that API to leave us some degree of
> > independence that QEMU implementation might evolve.  
> 
> That is certainly a different perspective, it would have been
> better to not express this idea as a FSM in that case...
> 
> So each state in mlx5vf_pci_set_device_state() should call the correct
> combination of (un)freeze, (un)quiesce and so on so each state
> reflects a defined operation of the device?

I'd expect so, for instance the implementation of entering the _STOP
state presumes a previous state that where the device is apparently
already quiesced.  That doesn't support a direct _RUNNING -> _STOP
transition where I argued in the linked threads that those states
should be reachable from any other state.  Thanks,

Alex