[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH v3 4/4] x86/PV: enable the emulated PIT
On 18/01/16 11:06, Jan Beulich wrote: >> Which gets us to the second, broader issue: These flags shouldn't >> be forced to a particular value during migration, but instead they >> should be part of the state getting migrated. Incoming domains >> then would - if the field is missing due to coming from an older >> hypervisor - have the flag default to 1. >>>> There is sadly another ratsnest here. >>> I've been afraid of that. >>> >>>> These values are needed for domain creation, which means that putting >>>> them anywhere in the migration stream is already too late, as the domain >>>> has been created before the stream header is read. >>> Is that an inherent requirement, or just a result of current code >>> structure? >> Depends. As far as libxc/libxl migration levels go, current code structure. > I.e. fixable. > >> Whatever (eventually) gets used to set these values will however be >> present in the xl configuration, which is at the very start of the >> stream, and is what is used to create the new domain. > Which makes me repeat the question: Is this an inherent property > or just "that's the way it is right now"? And then of course the > question arises whether setting those flags at domain creation time > is the right model. I.e. ... > >> We really don't want the libxc migrate code to be making the >> DOMCTL_createdomain hypercall itself; it opens up a whole new attack >> surface via cunningly-crafted save image. The best we can do is have a >> sanity check later on. > ... what about deriving the emulation flags from the various > pieces of state getting loaded, at least when there are matching > pairs (which namely is the case for PIT)? How would you suggest setting theses flags up in the plain domain build case then? ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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