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[82.30.61.225]) by smtp.gmail.com with ESMTPSA id d1sm18850117wrr.72.2021.10.26.01.40.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Oct 2021 01:40:36 -0700 (PDT) Date: Tue, 26 Oct 2021 09:40:34 +0100 From: "Dr. David Alan Gilbert" To: Jason Gunthorpe Cc: Alex Williamson , Yishai Hadas , 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, Cornelia Huck Subject: Re: [PATCH V2 mlx5-next 12/14] vfio/mlx5: Implement vfio_pci driver for mlx5 devices Message-ID: References: <20211019124352.74c3b6ba.alex.williamson@redhat.com> <20211019192328.GZ2744544@nvidia.com> <20211019145856.2fa7f7c8.alex.williamson@redhat.com> <20211019230431.GA2744544@nvidia.com> <5a496713-ae1d-11f2-1260-e4c1956e1eda@nvidia.com> <20211020105230.524e2149.alex.williamson@redhat.com> <20211025115535.49978053.alex.williamson@redhat.com> <20211025191509.GB2744544@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211025191509.GB2744544@nvidia.com> User-Agent: Mutt/2.0.7 (2021-05-04) Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org * Jason Gunthorpe (jgg@nvidia.com) wrote: > On Mon, Oct 25, 2021 at 07:47:29PM +0100, Dr. David Alan Gilbert wrote: > > > It may need some further refinement; for example in that quiesed state > > do counters still tick? will a NIC still respond to packets that don't > > get forwarded to the host? > > At least for the mlx5 NIC the two states are 'able to issue outbound > DMA' and 'all internal memories and state are frozen and unchanging'. Yeh, so my point was just that if you're adding a new state to this process, you need to define the details like that. Dave > The later means it should not respond/count/etc to network packets > either. > > Roughly it is > 'able to mutate external state' / 'able to mutate internal state' > > The invariant should be that successive calls to serialize the > internal state while frozen should return the same serialization. > > We may find that migratable PCI functions must have some limited > functionality. Ie anything with a realtime compoment - for instance a > sync-ethernet clock synchronization control loop, may become > challenging to migrate without creating a serious functional > distortion. > > Jason > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK