How to handle TLB shootdown IPI on Xen

From: J Ahn <jeong.seob.ahn@gmail.com>
To: xen-devel@lists.xen.org
Subject: How to handle TLB shootdown IPI on Xen
Date: Mon, 12 Aug 2013 01:22:30 +0900	[thread overview]
Message-ID: <CAFgwMgoBxiektxmjMDGvE1W9fGthoiiY=Zt598c+g8+1QC+_rw@mail.gmail.com> (raw)

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All,

Currently, I have used Xen 4.2.1 with Ubuntu HVM guests.

I am just wondering how to handle the TLB shootdown IPIs in Xen.
Specifically, the guest will send the TLB shootdown IPI to remote CPUs if
TLB synchronization between CPUs is required.

In this case, I guess the hypervisor intervention is required because it
needs to route the interrupt to virtual CPUs of corresponding guest.
However, Xen seems not to intercept the event because the number of IPIs
from Xenperf is very low. Is this right?

I checked the number of IPIs is relatively high in guest OS when using 'cat
/proc/interrupts'.
I also checked the system does not invoke the '*invalidate_interrupt*'
function located in *'arch/x86/smp.c*'.

If there is no need to intervene to deal with that, could anyone explain
that how to maintain the consistent view of TLBs in the guest hosted by Xen?
Otherwise, please let me know the handling TLB shootdown IPI code in Xen.

Thanks

Jeongseob

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