From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: KVM handling external interrupts Date: Thu, 07 Jun 2012 17:07:03 +0200 Message-ID: <4FD0C397.9060607@web.de> References: <4FD062BC.5090703@web.de> <4FD09349.6090305@web.de> <4FD09C42.8080201@web.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigD5C77508132E5E75A4033263" Cc: Alex Landau , Dan Tsafrir , sheng qiu , kvm , kvm-owner@vger.kernel.org, Muli Ben-Yehuda , Nadav Har'El , Nadav Amit To: Abel Gordon Return-path: Received: from mout.web.de ([212.227.17.11]:49880 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753522Ab2FGPHJ (ORCPT ); Thu, 7 Jun 2012 11:07:09 -0400 In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigD5C77508132E5E75A4033263 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 2012-06-07 14:32, Abel Gordon wrote: > kvm-owner@vger.kernel.org wrote on 07/06/2012 15:19:14: >=20 >>>> The guest can still mask interrupts above that limit via cli, no? >>>> So the only measures that save us from CPU hogging guests are the >>>> preemption timer and kicking via NMI. Or what am I missing? >>> >>> Nothing :) As we described in the paper, this is what we do to avoid >>> this situation. >> >> So the other measures are redundant, right? They only seem to complica= te >> the approach without any gain, that is my point. >=20 > We described in the paper all the mechanisms we thought could be used. Which of them did you implement and validate so far? > Which mechanisms are sufficient/preferable/simpler ? I think we are ba= ck > to the KVM<->Linux dependencies and whenever we are talking about > hypervisors in general or a specific implementation for KVM. I don't think this depends on KVM vs. whatever hypervisor, these are pretty generic considerations. If you need the preemption timer for breaking out of cli anyway, why play tricks with off-limit vectors? NMIs can be useful to accelerate the preemption when some other core wants to deliver an IPI (to kick the target out of guest mode and to reenable interrupts, not to process them)= =2E Jan --------------enigD5C77508132E5E75A4033263 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAk/Qw5cACgkQitSsb3rl5xTJvQCfWjdj598hJmaIR4qc3+Cuern2 4aEAoK+luAx7LVi7rM13InKcCmnW1UjN =eJ8v -----END PGP SIGNATURE----- --------------enigD5C77508132E5E75A4033263--