Re: [PATCH 1/5] x86/ibrs: Introduce native_rdmsrl, and native_wrmsrl

[Andy Lutomirski]

On Thu, Jan 11, 2018 at 9:03 PM, Dave Hansen <dave.hansen@xxxxxxxxx> wrote:
> On 01/11/2018 07:01 PM, Raj, Ashok wrote:
>> On Thu, Jan 11, 2018 at 06:20:13PM -0800, Andy Lutomirski wrote:
>>> On Thu, Jan 11, 2018 at 5:52 PM, Raj, Ashok <ashok.raj@xxxxxxxxx> wrote:
>>>>>
>>>>> What's wrong with native_read_msr()?
>>>>
>>>> Yes, i think i should have added to msr.h. The names didn't read as a
>>>> pair, one was native_read_msr, wrmsrl could be taken over when paravirt is
>>>> defined?
>>>
>>> Why do you need to override paravirt?
>>
>> The idea was since these MSR's are passed through we shouldn't need to
>> handle them any differently. Also its best to do this as soon as possible
>> and avoid longer paths to get this barrier to hardware.
>
> We were also worried about the indirect calls that are part of the
> paravirt interfaces when retpolines are not in place.
>

How could those possibly be any worse than any other indirect call in
the kernel?