On 01/10/2019 09:46, Jan Beulich wrote: > On 01.10.2019 10:28, Paul Durrant wrote: >> Now that xl.cfg has an option to explicitly enable IOMMU mappings for a >> domain, migration may be needlessly vetoed due to the check of >> is_iommu_enabled() in paging_log_dirty_enable(). >> There is actually no need to prevent logdirty from being enabled unless >> devices are assigned to a domain and that domain is sharing HAP mappings >> with the IOMMU (in which case disabling write permissions in the P2M may >> cause DMA faults). > But that's taking into account only half of the reason of the > exclusion. The other half is that assigned devices may cause pages > to be dirtied behind the back of the log-dirty logic.
No. Very specifically not. Xen cannot correctly evaluate whether a domain is migrateable or not, and therefore is unable to make a correct veto decision. The existing DOMCTL_disable_migrate is bogus and I'm in the process of purging it from Xen. Also, I seem to recall nacking this change originally, specifically on the basis that it breaks live migration with GPUs, so I'm rather confused to find the code present... ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
