> From: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> > Sent: Thursday, September 30, 2021 2:35 PM > > > From: Tian, Kevin [mailto:kevin.tian@xxxxxxxxx] > > Sent: 30 September 2021 01:42 > > > > > From: Shameerali Kolothum Thodi > > > <shameerali.kolothum.thodi@xxxxxxxxxx> > > > > > > > From: Tian, Kevin [mailto:kevin.tian@xxxxxxxxx] > > > > Sent: 29 September 2021 10:06 > > > > > > > > > From: Shameerali Kolothum Thodi > > > > > <shameerali.kolothum.thodi@xxxxxxxxxx> > > > > > > > > > > Hi Kevin, > > > > > > > > > > > From: Tian, Kevin [mailto:kevin.tian@xxxxxxxxx] > > > > > > Sent: 29 September 2021 04:58 > > > > > > > > > > > > Hi, Shameer, > > > > > > > > > > > > > From: Shameer Kolothum > <shameerali.kolothum.thodi@xxxxxxxxxx> > > > > > > > Sent: Wednesday, September 15, 2021 5:51 PM > > > > > > > > > > > > > > Hi, > > > > > > > > > > > > > > Thanks to the introduction of vfio_pci_core subsystem > framework[0], > > > > > > > now it is possible to provide vendor specific functionality to > > > > > > > vfio pci devices. This series attempts to add vfio live migration > > > > > > > support for HiSilicon ACC VF devices based on the new framework. > > > > > > > > > > > > > > HiSilicon ACC VF device MMIO space includes both the functional > > > > > > > register space and migration control register space. As discussed > > > > > > > in RFCv1[1], this may create security issues as these regions get > > > > > > > shared between the Guest driver and the migration driver. > > > > > > > Based on the feedback, we tried to address those concerns in > > > > > > > this version. > > > > > > > > > > > > This series doesn't mention anything related to dirty page tracking. > > > > > > Are you rely on Keqian's series for utilizing hardware iommu dirty > > > > > > bit (e.g. SMMU HTTU)? > > > > > > > > > > Yes, this doesn't have dirty page tracking and the plan is to make use > of > > > > > Keqian's SMMU HTTU work to improve performance. We have done > > basic > > > > > sanity testing with those patches. > > > > > > > > > > > > > Do you plan to support migration w/o HTTU as the fallback option? > > > > Generally one would expect the basic functionality ready before talking > > > > about optimization. > > > > > > Yes, the plan is to get the basic live migration working and then we can > > > optimize > > > it with SMMU HTTU when it is available. > > > > The interesting thing is that w/o HTTU vfio will just report every pinned > > page as dirty, i.e. the entire guest memory is dirty. This completely kills > > the benefit of precopy phase since Qemu still needs to transfer the entire > > guest memory in the stop-copy phase. This is not a 'working' model for > > live migration. > > > > So it needs to be clear whether HTTU is really an optimization or > > a hard functional-requirement for migrating such device. If the latter > > the migration region info is not a nice-to-have thing. > > Yes, agree that we have to transfer the entire Guest memory in this case. > But don't think that is a killer here as we would still like to have the > basic live migration enabled on these platforms and can be used > where the constraints of memory transfer is acceptable. > > > btw the fallback option that I raised earlier is more like some software > > mitigation for collecting dirty pages, e.g. analyzing the ring descriptors > > to build software-tracked dirty info by mediating the cmd portal > > (which requires dynamically unmapping cmd portal from the fast-path > > to enable mediation). We are looking into this option for some platform > > which lacks of IOMMU dirty bit support. > > Interesting. Is there anything available publicly so that we can take a look? > Not yet. Once we had an implementation based on an old approach before vfio-pci-core is ready. Now suppose it needs rework based on the new framework. +Shaopeng who owns this work. Thanks Kevin
