On 02/07/18 12:27, Jan Beulich wrote: >>>> On 02.07.18 at 11:57, <andrew.coop...@citrix.com> wrote: >> These MSRs are non-architectural and the available booleans were used in lieu >> of an architectural signal of availability. The MSRs are unconditionally >> available to HVM guests, but currently for PV guests, are hidden when CPUID >> faulting is unavailable. >> >> However, in hindsight, the additional booleans make toolstack MSR >> interactions >> more complicated. As the behaviour of the MSRs is reserved when unavailable, > Is it? Isn't the expected (mandated?) behavior raising of #GP(0) in that > case?
It is platform specific as to whether the MSR exists on not, and the only reasonable way to find out whether it is available is to try reading it. In practice, these MSRs appear to have existed since Netburst, and have a range of misc non-architectural functionality in them. These changes do make the MSRs unconditionally available from the guests point of view, but offering 0's is compatible with how a guest consumes the information. ~Andrew _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
