svn commit: r267651 - in head: share/man/man4 sys/dev/cpuctl sys/sys usr.sbin/cpucontrol

[Attilio Rao]

On Jun 20, 2014 9:49 AM, "Konstantin Belousov" <kostikbel at gmail.com> wrote:
>
> On Fri, Jun 20, 2014 at 08:12:59AM +0200, Attilio Rao wrote:
> > On Fri, Jun 20, 2014 at 6:08 AM, Konstantin Belousov
> > <kostikbel at gmail.com> wrote:
> > > On Thu, Jun 19, 2014 at 09:54:41PM +0000, Attilio Rao wrote:
> > >> Author: attilio
> > >> Date: Thu Jun 19 21:54:41 2014
> > >> New Revision: 267651
> > >> URL: http://svnweb.freebsd.org/changeset/base/267651
> > >>
> > >> Log:
> > >>   Following comments in r242565 add the possibility to specify ecx
when
> > >>   performing cpuid calls.
> > >>   Add also a new way to specify the level type to cpucontrol(8) as
> > >>   reported in the manpage.
> > >>
> > >>   Sponsored by:       EMC / Isilon storage division
> > >>   Reviewed by:        bdrewery, gcooper
> > >>   Testerd by: bdrewery
> > >> Modified: head/sys/sys/cpuctl.h
> > >>
==============================================================================
> > >> --- head/sys/sys/cpuctl.h     Thu Jun 19 21:05:07 2014
 (r267650)
> > >> +++ head/sys/sys/cpuctl.h     Thu Jun 19 21:54:41 2014
 (r267651)
> > >> @@ -35,7 +35,8 @@ typedef struct {
> > >>  } cpuctl_msr_args_t;
> > >>
> > >>  typedef struct {
> > >> -     int             level;  /* CPUID level */
> > >> +     int             level;          /* CPUID level */
> > >> +     int             level_type;     /* CPUID level type */
> > >>       uint32_t        data[4];
> > >>  } cpuctl_cpuid_args_t;
> > >>
> > >> @@ -50,5 +51,6 @@ typedef struct {
> > >>  #define      CPUCTL_UPDATE   _IOWR('c', 4, cpuctl_update_args_t)
> > >>  #define      CPUCTL_MSRSBIT  _IOWR('c', 5, cpuctl_msr_args_t)
> > >>  #define      CPUCTL_MSRCBIT  _IOWR('c', 6, cpuctl_msr_args_t)
> > >> +#define      CPUCTL_CPUID_COUNT _IOWR('c', 7, cpuctl_cpuid_args_t)
> > >>
> > >>  #endif /* _CPUCTL_H_ */
> > >
> > > The cpuctl(4) is used by third-party code, and this change breaks its
> > > ABI. The numeric value for CPUCTL_CPUID is changed, which means that
> > > old binaries call non-existing ioctl now. This is at least a visible
> > > breakage, since the argument for the ioctl changed the layout as well.
> > >
> > > The following patch restored the CPUCTL_CPUID for me.  I considered
> > > naming its argument differently, instead of renaming the argument
> > > of CPUCTL_CPUID_COUNT (which you tried to do ?), but decided not,
> > > to preserve the API as well.
> >
> > No, breaking the ABI is fine for -CURRENT so I don't see why we need
the bloat.
>
> No, breaking ABI is not fine at all, be it CURRENT or not. We try to
> keep the ABI stable, doing costly measures like symbol versioning, where
> applicable. Since this is a change to ABI for kernel interface, it
> cannot be covered by symver tricks and must be done in kernel.
>
> > I don't plan on MFC this patch. If I need to (or any user requests
> > that) I will do with the appropriate ABI-compliant way (ie. adding a
> > new argument like this one).
>
> Besides the same-world ABI issue, people run jails with lower world
> version on higher-versioned kernels.

I think you have a point,I forgot we have different requirements for ABI
and KBI/KPI in -CURRENT per jail. I will make a patch for it when I get
back home in few hours.

Attilio