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| /freebsd-9.3-release/sys/kern/ | ||
| H A D | subr_param.c | diff 186252 Wed Dec 17 18:09:16 MST 2008 ivoras Introduce a sysctl kern.vm_guest that reflects what the kernel knows about it running under a virtual environment. This also introduces a globally accessible variable vm_guest that can be used where appropriate in the kernel to inspect this environment. To make it easier for the long run, an enum VM_GUEST is also introduced, which could possibly be factored out in a header somewhere (but the question is where - vm/vm_param.h? sys/param.h?) so it eventually becomes a part of the standard KPI. In any case, it's a start. The purpose of all this isn't to absolutely detect that the OS is running under a virtual environment (cf. "redpill") but to allow the parts of the kernel and the userland that care about this particular aspect and can do something useful depending on it to have a standardised interface. Reducing kern.hz is one example but there are other things that could be done like avoiding context switches, not using CPU instructions that are known to be slow in emulation, possibly different strategies in VM (memory) allocation, CPU scheduling, etc. It isn't clear if the JAILS/VIMAGE functionality should also be exposed by this particular mechanism (probably not since they're not "full" virtual hardware environments). Sometime in the future another sysctl and a variable could be introduced to reflect if the kernel supports any kind of virtual hosting (e.g. VMWare VMI, Xen dom0). Reviewed by: silence from src-commiters@, virtualization@, kmacy@ Approved by: gnn (mentor) Security: Obscurity doesn't help. |
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