lkml.org 
[lkml]   [2018]   [Jun]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC PATCH 7/8] x86/lib_user_wait.h: Add APIs for user wait instructions
On Tue, 19 Jun 2018, Fenghua Yu wrote:
> On Tue, Jun 19, 2018 at 11:12:05AM +0200, Thomas Gleixner wrote:
> > On Fri, 15 Jun 2018, Fenghua Yu wrote:
> >
> > > A few new user wait instructions UMONITOR, UMWAIT, and TPAUSE are
> > > published in the latest Intel Instruction Set Extensions document.
> > >
> > > Define the APIs for user or kernel to use the instructions.
> >
> > You're not defining APIs. You're adding a pile of misdesigned helper
> > functions which again add static storage per compilation unit and CPUID
> > fiddling.
> >
> > If you want to add proper APIs then add the stuff to the VDSO and be done
> > with it.
>
> The user wait instructions are mainly called by user apps; but they can
> be used in kernel as well.
>
> I'm planning to provide five APIs to user:
> 1. If user wait feature is supported
> 2. nsec to tsc translation
> 3. umonitor function that exectes UMONITOR instruction
> 4. umwait function that executes UMWAIT instruction
> 5. tpause function that executes TPAUSE instruction
>
> Seems 1-2 can be implemented in VDSO. But should I implement 3-5 in
> VDSO/kernel as well?

If you want a real API, then yes. If not, then an UAPI header is definitely
not the place for this.

Thanks

tglx

\
 
 \ /
  Last update: 2018-06-20 00:35    [W:0.117 / U:1.356 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site