[Qemu-devel] Question on cpu_interrupt()

[Jiaqing Du]

Hi,

I am trying to inject NMIs to a guest running in QEMU by using
cpu_interrupt(). I notice that QEMU slows down significantly when NMIs
are being injected.

The injected NMIs per second is around 10. QEMU is pined to one core.
A computation intensive application runs in the guest. When no NMIs
are being injected, the physical CPU utilization is 100%; while NMIs
are injected by calling cpu_interrupt(), the physical CPU utilization
rate drops to around 30%. As far as I know from reading the code,
cpu_interrupt() unchains the translation cache. So when the current TB
is executed over, QEMU code is executed to handle the interrupt. I
also notice that cpu_interrupt() is called very frequently normally.
Why QEMU's performance drops so much when NMIs are being injected?

Please CC me your reply.


Thanks,
Jiaqing