Re: [Xen-devel] [PATCH v1 for 4.7] x86/cpuid: fix raw FEATURESET_7d0 reporting

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.05.18 at 17:36, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 15/05/18 10:04, Jan Beulich wrote:
>>>>> On 15.05.18 at 10:37, <sergey.dyasli@xxxxxxxxxx> wrote:
>>> Commit 62b1879693e0 ("x86: further CPUID handling adjustments") added
>>> FEATURESET_7d0 reporting but forgot to update calculate_raw_featureset()
>>> function. As result, the value reported by xen-cpuid contains 0.
>>>
>>> Fix that by properly filling raw_featureset[FEATURESET_7d0].
>>>
>>> Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
>> Thanks, technically
>> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
>>
>>> ---
>>> I see that at least 4.8 also contains this bug, so other releases also
>>> need checking.
>> The commit in question being only on the two branches, I think no other one
>> would need the change.
>>
>> I'm certainly going to apply this to 4.8; I'm uncertain about 4.7 though 
> <snip>
> 
> The entirety of that changeset is broken in feature levelling scenarios,
> which is a consequence of missing this hunk which Sergey identified.
> 
> The result is that, when trying to level STIBP/IBPB out of guests view,
> the CPUID bits remain visible, but attempts to use the MSR bits will fail.

I don't follow: PV and HVM feature sets take host_featureset as an input,
not raw_featureset.

Jan



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