Re: [Xen-devel] PC8 Residency on Broadwell hardware

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.09.16 at 19:28, <jun.nakajima@xxxxxxxxx> wrote:

Please try to get quoting right - your response was rather hard to
follow.

> On Sep 12, 2016, at 2:00 AM, Jan Beulich 
> <JBeulich@xxxxxxxx<mailto:JBeulich@xxxxxxxx>> wrote:
> 
> On 12.09.16 at 10:47, 
> <andrew.cooper3@xxxxxxxxxx<mailto:andrew.cooper3@xxxxxxxxxx>> wrote:
> c/s 350bc1a9d4 "x86: support newer Intel CPU models" changed the set of
> MSRs read by Xeon Broadwell hardware (specifically, model 79 / 0x47).

I think this was misleading: 79 == 0x4f. Andrew, can you confirm in
your case please?

> 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).

Yes.

> 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.”

Model 0x4f is what we're talking about, and table 35-36 has the information
on MSR_PKG_C8_RESIDENCY (630H).

Jan

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