Re: [libvirt] [PATCH 00/10] conf: Clean up virDomain*Def creation

> Isolation groups are used to make sure any given device ends > up on the same bus as related devices and on a different bus > as unrelated devices. >  > They're an abstract concept, and while working on the initial > implementation it just happened to be convenient for me to > have the isolation group match the IOMMU group. There's no > specific reason that has to be the case.   Fair enough. The documentation you are adding in the linked series is vague enough to alow this meaning too:   @@ -164,6 +164,16 @@ struct _virDomainDeviceInfo {        */       int pciConnectFlags; /* enum virDomainPCIConnectFlags */       char *loadparm; + +    /* PCI devices will only be automatically placed on a PCI bus +     * that shares the same isolation group */ +    int isolationGroup; + +    /* Usually, PCI buses will take on the same isolation group +     * as the first device that is plugged into them, but in some +     * cases we might want to prevent that from happening by +     * locking the isolation group */ +    bool isolationGroupLocked;   };

> We're never converting back and forth between the two, which > I agree would end up in misery at some point down the line; > we just set the isolation group once per device and then just > perform comparison between isolation groups from there on.   I'd suggest you create a helper to assign those then (be it from IOMMU group or something else), so there's at least a single point that can be referenced in the future and which will explain this reasoning.

Also adding a note that 0 means the device is not isolated would make sense in the structure above.