Re: [Xen-devel] [PATCH 2/4] x86/setup: Minor cleanup to host SYSCALL MSR handling

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 13.02.17 at 16:33, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 13/02/17 15:30, Jan Beulich wrote:
>>>>> On 13.02.17 at 16:26, <andrew.cooper3@xxxxxxxxxx> wrote:
>>> On 13/02/17 15:19, Jan Beulich wrote:
>>>>>>> On 13.02.17 at 15:32, <andrew.cooper3@xxxxxxxxxx> wrote:
>>>>> Xen's choice of the MSR_STAR value is constant across all pcpus.  
>>>>> Introduce a
>>>>> new define and use it to avoid the opencoding in 
>>>>> subarch_percpu_traps_init()
>>>>> and restore_rest_processor_state().
>>>>>
>>>>> Despite Intel hardware having an MSR_CSTAR register, nothing actually 
>>>>> uses it
>>>>> as the SYSCALL instruction raises #UD out of 64bit mode, meaning that
>>>> Did you mean "32-bit"?
>>> SYSCALL on Intel will #UD if CS.L == 0, so you can't even use it from a
>>> compatability mode segment.
>> Right - so my comment stands. Or did you mean "outside of 64-bit
>> mode"?
> 
> I did, but I don't see how that is meaningfully different from what I wrote.

Interesting, you'll have to correct my English understanding then:
"out of <something>" to me so far meant originating in <something>,
quite the opposite of "outside of <something>".

Jan


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