Re: [Xen-devel] [PATCH for-4.11] x86: Use spec_ctrl_{enter, exit}_idle() in the S3/S5 path

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 18.04.18 at 18:02, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 18/04/18 16:43, Jan Beulich wrote:
>>>>> On 18.04.18 at 12:43, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> This avoids opencoding the functionality (and missing one bit of it), and 
>>> and
>>> some comments explaining what is going on.
>> Missing which bit of it? The MSR writes aren't strictly necessary afaict, and
>> functionally clearing bti_ist_info is all that's needed for the entry path of
>> interest, while clearing use_shadow_spec_ctrl is all that's needed for the
>> exit-to-Xen path. Hence I'm don't see (yet) what bug it is you think this
>> fixes.
> 
> It is expected that we don't hand off control to the firmware in cases
> like this with the mitigations in place.  Here, it doesn't actually
> matter too much, but there is no point having the mitigations in effect
> when we're the final CPU and trying to shut down.

With an improved description the patch can certainly have my R-b; the
code change itself is clearly fine with me.

Jan



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