On Sat, 4 Apr 2009, Matthias Kaehlcke wrote: > hi robert, > > El Sat, Apr 04, 2009 at 08:02:29AM -0400 Robert P. J. Day ha dit: > > > is there an easy way to tell if a running kernel has KVM > > functionality? from "make menuconfig", we can see the KVM tristate > > selections under "Virtualization:" > > > > --- Virtualization > > <M> Kernel-based Virtual Machine (KVM) support > > < > KVM for Intel processors support (NEW) > > < > KVM for AMD processors support (NEW) > > > > so if i have no access to the corresponding config file, how can i > > tell if a kernel has any or all of the above? > > > > first, i know that if you choose to build all of the above as > > modules, you'll get kvm.ko, kvm-intel.ko and kvm-amd.ko, so i can > > check the modules. but if any of that has been built into the kernel, > > is there a way to tell? something under /proc, perhaps? > > kvm_init() registers the device class 'kvm': > http://lxr.linux.no/linux+v2.6.29/virt/kvm/kvm_main.c#L2289 > > i guess it is called at system initialization when kvm support has > been built into the kernel. if that is the case you could check for > the existence of /sys/class/kvm ah, quite right, i should have checked there. and let me ask a couple more questions, which i would normally answer for myself by testing but, at the moment, i have no system running a kernel with built-in kvm support. (as an aside, is anyone out there running a recent kernel with built-in kvm that can verify the above?) if you look at the menuconfig snippet above, you can see that, in addition to selecting *generic* kvm support, this still won't do you any good unless you further select one of the two available (x86-based) kvm hardware extensions (Intel vmx or AMD svm). so, the obvious questions: * i'm assuming that it's *legal* to select generic kvm support without selecting additional CPU-specific support, which will only mean that, if matthias is correct, you'll see /sys/class/kvm even when you have no actual kvm support. * depending on which of the two (or possibly both) CPU-specific virt support you choose, how could you verify that *those* were currently supported in your running kernel? if they were built modular, i can already see that you'd have the modules kvm-intel.ko or kvm-amd.ko. but if they're built in, how could you tell? would they show up as subdirs under /sys/class/kvm? again, anyone who can verify this on an actual system, feel free. thanks. rday -- p.s. depending on which CPU support you choose, you'd end up compiling one or both of arch/x86/kvm/{svm,vmx}.c. i guess i could just peruse those source files and see if they register something under /sys. ======================================================================== Robert P. J. Day Linux Consulting, Training and Annoying Kernel Pedantry: Have classroom, will lecture. http://crashcourse.ca Waterloo, Ontario, CANADA ======================================================================== -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
