cvs commit: src/share/man/man4 Makefile cpuctl.4 src/sys/amd64/amd64 support.S src/sys/amd64/conf NOTES src/sys/amd64/include cpufunc.h specialreg.h src/sys/conf files.amd64 files.i386 src/sys/dev/cpuctl cpuctl.c ...

[John Baldwin]

On Friday 08 August 2008 02:51:33 pm Kostik Belousov wrote:
> On Fri, Aug 08, 2008 at 02:27:42PM -0400, John Baldwin wrote:
> > On Friday 08 August 2008 02:10:52 pm Kostik Belousov wrote:
> > > On Fri, Aug 08, 2008 at 12:51:17PM -0400, John Baldwin wrote:
> > > > On Friday 08 August 2008 12:26:53 pm Stanislav Sedov wrote:
> > > > > stas        2008-08-08 16:26:53 UTC
> > > > > 
> > > > >   FreeBSD src repository
> > > > > 
> > > > >   Modified files:
> > > > >     share/man/man4       Makefile 
> > > > >     sys/amd64/amd64      support.S 
> > > > >     sys/amd64/conf       NOTES 
> > > > >     sys/amd64/include    cpufunc.h specialreg.h 
> > > > >     sys/conf             files.amd64 files.i386 
> > > > >     sys/i386/conf        NOTES 
> > > > >     sys/i386/i386        support.s 
> > > > >     sys/i386/include     cpufunc.h specialreg.h 
> > > > >     sys/modules          Makefile 
> > > > >     sys/sys              priv.h 
> > > > >     usr.sbin             Makefile 
> > > > >   Added files:
> > > > >     share/man/man4       cpuctl.4 
> > > > >     sys/dev/cpuctl       cpuctl.c 
> > > > >     sys/modules/cpuctl   Makefile 
> > > > >     sys/sys              cpuctl.h 
> > > > >     usr.sbin/cpucontrol  Makefile amd.c amd.h cpucontrol.8 
> > > > >                          cpucontrol.c cpucontrol.h intel.c intel.h 
> > > > >   Log:
> > > > >   SVN rev 181430 on 2008-08-08 16:26:53Z by stas
> > > > >   
> > > > >   - Add cpuctl(4) pseudo-device driver to provide access to some 
> > low-level
> > > > >     features of CPUs like reading/writing machine-specific 
registers,
> > > > >     retrieving cpuid data, and updating microcode.
> > > > >   - Add cpucontrol(8) utility, that provides userland access to
> > > > >     the features of cpuctl(4).
> > > > >   - Add subsequent manpages.
> > > > >   
> > > > >   The cpuctl(4) device operates as follows. The pseudo-device node 
> > cpuctlX
> > > > >   is created for each cpu present in the systems. The pseudo-device 
> > minor
> > > > >   number corresponds to the cpu number in the system. The cpuctl(4) 
> > pseudo-
> > > > >   device allows a number of ioctl to be preformed, namely 
> > RDMSR/WRMSR/CPUID
> > > > >   and UPDATE. The first pair alows the caller to read/write 
> > machine-specific
> > > > >   registers from the correspondent CPU. cpuid data could be 
retrieved 
> > using
> > > > >   the CPUID call, and microcode updates are applied via UPDATE.
> > > > >   
> > > > >   The permissions are inforced based on the pseudo-device file 
> > permissions.
> > > > >   RDMSR/CPUID will be allowed when the caller has read access to the 
> > device
> > > > >   node, while WRMSR/UPDATE will be granted only when the node is 
opened
> > > > >   for writing. There're also a number of priv(9) checks.
> > > > >   
> > > > >   The cpucontrol(8) utility is intened to provide userland access to
> > > > >   the cpuctl(4) device features. The utility also allows one to 
apply
> > > > >   cpu microcode updates.
> > > > >   
> > > > >   Currently only Intel and AMD cpus are supported and were tested.
> > > > 
> > > > Note that cpuid isn't a privileged instruction, so I'm not sure it's 
> > really 
> > > > worth having an ioctl for that particular case.
> > > 
> > > It was discussed when patch was reviewed on current at . The ioctl allows
> > > to get cpuid information for specific processor, as opposed to some
> > > random core curthread happens to run ATM.
> > 
> > You can achieve that now with cpuset. :)  (See my ping-pong test program 
> > recently which used cpuid to fetch the APIC ID to test for ping-ponging in 
> > the scheduler.)
> 
> If this is a backout request (for cpuid functionality) then we will do it.
> 
> But I considered it much easier and cleaner to do
> 	fd = open("/dev/cpuctlN", O_RDWR);
> 	ioctl(fd, CPUCTL_CPUID, &x);
> 	if (x.y)
> 		ioctl(fd, CPUCTL_WRMSR, ...);
> 	close(fd);
> then
> 	fd = open("/dev/cpuctlN", O_RDWR);
> 	cpuset(...); /* bind to cpu */
> 	__asm__("cpuid" : =0 (x));
> 	if (x.y)
> 		ioctl(fd, CPUCTL_WRMSR, ...);
> 	cpuset(...); /* restore prev mask */
> 	close(fd);

You can leave it.  It is useful to specify the CPU I suppose.

-- 
John Baldwin