Date: Fri, 8 Aug 2008 14:59:54 -0400 From: John Baldwin <jhb@freebsd.org> To: Kostik Belousov <kostikbel@gmail.com> Cc: Stanislav Sedov <stas@freebsd.org>, cvs-src@freebsd.org, src-committers@freebsd.org, cvs-all@freebsd.org Subject: Re: 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 ... Message-ID: <200808081459.54735.jhb@freebsd.org> In-Reply-To: <20080808185133.GG97161@deviant.kiev.zoral.com.ua> References: <200808081631.m78GVG9i088754@repoman.freebsd.org> <200808081427.42536.jhb@freebsd.org> <20080808185133.GG97161@deviant.kiev.zoral.com.ua>
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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@. 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
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