Dong, Eddie wrote: > [EMAIL PROTECTED] wrote: >> Hi, >> >> I'm seeing fairly high vm-exit latencies (300-400 us) during and only >> during qemu/kvm startup and shutdown on a Core2 T5500 in 32-bit mode. >> It's most probably while the VM runs inside bios code. During the rest >> of the time, while some Linux guest is running, the exit latencies are >> within microseconds, thus perfectly fine for the real-time scenarios >> I have in mind. > > How is this time spent? All in Qemu?
Most probably. I have a function tracer installed, and it does not report any kernel function call between the begin of the asm block and its end. > Usually a kernel only VM Exit cost less than 1us. That's what I'm seeing for the rest as well. I have read that certain guest states do not allow preemptions by external interrupts (here it is the timer IRQ), but both GUEST_INTERRUPTIBILITY_INFO and GUEST_ACTIVITY_STATE are 0 on entry, e.g. Is there a way for the guest to trigger a non-preemptible SMM entry, and that without the kernel noticing it? Jan
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