[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] x2APIC MSR range (XSA-108 follow-up)
On Mon, Oct 13, 2014 at 07:45:58AM +0100, Jan Beulich wrote: > All, > > during the embargo period of XSA-108 Matt pointed out that restricting > the emulated MSR range to 0x800-0x8ff isn't necessarily the ultimately > correct thing to do (as also noted in commit 61fdda7acf's description): > The x2APIC MSR range really is being specified as 0x800-0xbff, as > opposed to the range considered for virtualization purposes > (0x800-0x8ff). In order to determine proper behavior here we'd like to > get clarification from you, particularly also in the light of probing real > hardware pointing out the existence of (at least) MSRs 0xa00-0xa02. I recall the MSRs in question being 0xa00 and 0xa01. Perhaps 0xa02 also provided a value, but I'm not as sure. > With what we currently do (kind of supported by their values at least > not differing across physical CPUs on the probed systems) their values > are getting passed through to guests. The alternative of forcing #GP > for accesses to them as one could imply from the spec seems > undesirable: Guests may imply their existence based on CPU model. > Hence the only apparent reasonable alternative would be to provide > proper virtualization for these registers, requiring to know their > purpose. As MSRs that are not publicly documented, I suspect that 0xa00 and 0xa01 don't have semantics that have meaning in the virtualization context. Confirmation from Intel is welcome so we can determine the right path. --msw _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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