> -----Original Message----- > From: Tian, Kevin [mailto:kevin.tian@xxxxxxxxx] > Sent: 30 September 2021 01:42 > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx>; > kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; > linux-crypto@xxxxxxxxxxxxxxx > Cc: alex.williamson@xxxxxxxxxx; jgg@xxxxxxxxxx; mgurtovoy@xxxxxxxxxx; > Linuxarm <linuxarm@xxxxxxxxxx>; liulongfang <liulongfang@xxxxxxxxxx>; > Zengtao (B) <prime.zeng@xxxxxxxxxxxxx>; Jonathan Cameron > <jonathan.cameron@xxxxxxxxxx>; Wangzhou (B) > <wangzhou1@xxxxxxxxxxxxx>; He, Shaopeng <shaopeng.he@xxxxxxxxx>; Zhao, > Yan Y <yan.y.zhao@xxxxxxxxx> > Subject: RE: [PATCH v3 0/6] vfio/hisilicon: add acc live migration driver > > > 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? Thanks, Shameer
