Re: [PATCH 2/9] x86: Add support for rd/wr fs/gs base

[Andy Lutomirski]

On Mon, Mar 21, 2016 at 9:16 AM, Andi Kleen <andi@xxxxxxxxxxxxxx> wrote:
> From: Andi Kleen <ak@xxxxxxxxxxxxxxx>
>
> Introduction:
>
> IvyBridge added four new instructions to directly write the fs and gs
> 64bit base registers. Previously this had to be done with a system
> call to write to MSRs. The main use case is fast user space threading
> and switching the fs/gs registers quickly there. Another use
> case is having (relatively) cheap access to a new address
> register per thread.

I'm queuing up a variant of this patch.  I'll send it out for review
when it's ready.

--Andy