Re: [PATCH RFC V2 3/5] kvm hypervisor : Add two hypercalls to supportpv-ticketlock
From: Avi Kivity
Date: Mon Oct 24 2011 - 09:10:30 EST
On 10/24/2011 02:27 PM, Srivatsa Vaddagiri wrote:
> Good point. Assuming yield_on_hlt=1, that would allow the vcpu to be put
> to sleep and let other vcpus make progress.
> I guess with that change, we can also dropthe need for other hypercall
> introduced in this patch (kvm_pv_kick_cpu_op()). Essentially a vcpu sleeping
> because of HLT instruction can be woken up by a IPI issued by vcpu releasing a
Not if interrupts are disabled. My original plan was to use NMIs for
wakeups, but it turns out NMIs can be coalesced under certain rare
circumstances; this requires workarounds by the generic NMI code that
make NMIs too slow.
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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