On Sep 12, 2016, at 2:00 AM, Jan Beulich > wrote: On 12.09.16 at 10:47, > wrote: c/s 350bc1a9d4 "x86: support newer Intel CPU models" changed the set of MSRs read by Xeon Broadwell hardware (specifically, model 79 / 0x47). Rereading the manual, it does indeed indicate that this MSR is available. However, experimentally it is not. All Broadwell hardware XenServer has (both SDPs and production systems) reliably take a #GP fault when trying to read this MSR. Haswell hardware appears fine (and indeed, was reading that MSR before). Where did you find the info? I think you are talking about MSR_PKG_C8_RESIDENCY (630H). The SDM says (35.13): "Processors with signatures 06_3DH and 06_47H support the MSR interfaces listed in Table 35-18, Table 35-19, Table 35-20, Table 35-23, Table 35-27, Table 35-28, Table 35-32, and Table 35-33.” Intel: Please can you confirm whether the documentation is correct? If it is, do you have any idea why the MSR might not be available? I can't spot anything relevant in the platform errata documents. And indeed I had requested this same information already well over a week ago, without having heard back. Sorry, it seems that the email was buried in the pile of the emails that I received while I was in Toronto. Jan --- Jun Intel Open Source Technology Center