On Sat, May 17, 2008 at 06:26:01PM +0100, Rui Paulo wrote: > Andriy Gapon wrote: > >on 17/05/2008 18:37 Rui Paulo said the following: > >>Andriy Gapon wrote: > >>> > >>>It seems that rdmsr instruction can be executed only at the highest > >>>privilege level and thus is not permitted from userland. Maybe we > >>>should provide something like Linux /dev/cpu/msr? > >>>I don't like interface of that device, I think that ioctl approach > >>>would be preferable in this case. > >>>Something like create /dev/cpuN and allow some ioctls on it: > >>>ioctl(cpu_fd, CPU_RDMSR, arg). > >>>What do you think? > >>> > >> > >>While I think this (devcpu) is good for testing and development, I > >>prefer having a device driver to handle that specific MSR than a > >>generic /dev/cpuN where you can issue MSRs. > >>Both for security and reliability reasons. > > > >What about /dev/pci, /dev/io? Aren't they a precedent? > > They are, but, IMHO, we should no longer continue to create this type of > interfaces.
Why ? Are developers some kind of the second-class users ? I would have no opinion on providing /dev/cpu by the loadable module, not compiled into GENERIC. But the interface itself is useful at least for three things: - CPU identification (see x86info or whatever it is called); - CPU tweaking for bugs workaround without patching the kernel; - updating the CPU microcode. None of these is limited to the developers only. I am interested why Stanislav still did not submitted it for inclusion into the base still. Maybe, some other reasons exist.
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