Date: Sun, 18 May 2008 16:50:28 +0100 From: Rui Paulo <rpaulo@FreeBSD.org> To: Mike Meyer <mwm-keyword-freebsdhackers2.e313df@mired.org> Cc: freebsd-hackers@freebsd.org Subject: Re: rdmsr from userspace Message-ID: <48305044.7000007@FreeBSD.org> In-Reply-To: <20080517133037.3a3935db@bhuda.mired.org> References: <482E93C0.4070802@icyb.net.ua> <20080517133037.3a3935db@bhuda.mired.org>
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Mike Meyer wrote: > On Sat, 17 May 2008 11:13:52 +0300 > Andriy Gapon <avg@icyb.net.ua> 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? > > Ok, this points directly at a question I've been wondering about, but > haven't been able to find an answer in the google. > > I've been mucking about with general access to sysctl's (a sysctl > plugin for gkrellm, and a python module for accessing sysctls), and > with that hammer in my hand, the nail for this problem is obviously a > dev.cpu.#.msr sysctl. How can you request a rdmsr within the sysctl tree? I don't think sysctl is appropriate here either. -- Rui Paulo
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