I am presently working with Model Specific Registers and have been studying the kernel module implementation found in arch/x86/kernel/msr.c. I am attempting to understand what the implementation of the msr_ioctl(X86_IOC_RDMSR_REGS) <http://lxr.free-electrons.com/source/arch/x86/kernel/msr.c?v=3.8#L124> call is doing. msr_ioctl(X86_IOC_RDMSR_REGS) calls rdmsr_safe_regs_on_cpu() <http://lxr.free-electrons.com/source/arch/x86/lib/msr-smp.c#L242> (arch/x86/lib/msr-smp.c, line 180) which sets up __rdmsr_safe_regs_on_cpu <http://lxr.free-electrons.com/source/arch/x86/lib/msr-smp.c#L228>() (arch/x86/lib/msr-smp.c, line 166) as a callback function to perform the actual work. This callback function then calls rdmsr_safe_regs(). I am unable to find the implementation for rdmsr_safe_regs(). lxr <http://lxr.free-electrons.com/ident?i=rdmsr_safe_regs> only mentions references and a prototype definition. I've also manually grepped through the entire kernel source tree and have not been able to find where rdmsr_safe_regs is defined. I have poked around online, but have so far not been able to generate the correct query to find an answer. Can someone point me to the right documentation where I can figure this out? Thanks, Marty