From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [Android-virt] [PATCH v3 1/8] ARM: KVM: Initial skeleton to compile KVM support Date: Sun, 05 Jun 2011 19:48:37 +0200 Message-ID: <4DEBC175.4060007@web.de> References: <20110603150318.17011.82777.stgit@ubuntu> <4DE8FE38.6030405@siemens.com> <4DE90397.5080801@siemens.com> <4DEB74DA.2040909@redhat.com> <4DEB8F22.1020802@web.de> <4DEB9033.9060109@redhat.com> <4DEB998E.1010805@web.de> <4DEB9C60.1030001@redhat.com> <4DEB9D4A.9060702@web.de> <4DEBAE9F.2010400@redhat.com> <21338E26-01D2-4A1A-816B-2D596EC557B8@suse.de> <4DEBAFD4.7040208@redhat.com> <4136FD10-CE47-47B6-9C38-78BE2EA89028@suse.de> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigF03A454143EB509360DB9FDA" Cc: Avi Kivity , Christoffer Dall , kvm@vger.kernel.org, a.costa@virtualopensystems.com, android-virt@lists.cs.columbia.edu, s.raho@virtualopensystems.com To: Alexander Graf Return-path: Received: from fmmailgate02.web.de ([217.72.192.227]:47950 "EHLO fmmailgate02.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753325Ab1FERsn (ORCPT ); Sun, 5 Jun 2011 13:48:43 -0400 In-Reply-To: <4136FD10-CE47-47B6-9C38-78BE2EA89028@suse.de> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigF03A454143EB509360DB9FDA Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 2011-06-05 19:19, Alexander Graf wrote: >=20 > On 05.06.2011, at 18:33, Avi Kivity wrote: >=20 >> On 06/05/2011 07:30 PM, Alexander Graf wrote: >>>>> >>>>> Could you elaborate what you mean here? I'm not really following. = Are >>>>> you suggesting a new arch-generic interface? (Pardon my ignorance)= =2E >>>> >>>> Using KVM_IRQ_LINE everywhere except s390, not just in x86 and ARM.= >>> >>> An in-kernel MPIC implementation is coming for PPC, so I don't see an= y reason to switch from something that works now. >> >> Right, this is spilled milk. >> >> Does the ppc qemu implementation raise KVM_INTERRUPT solely from the v= cpu thread? >=20 > Well, without iothread it used to obviously. Now that we have an iothre= ad, it calls ioctl(KVM_INTERRUPT) from a separate thread. The code also d= oesn't forcefully wake up the vcpu thread, so yes, I think here's a chanc= e for at least delaying interrupt delivery. Chances are pretty slim we do= n't get out of the vcpu thread at all :). There are good chances to run into a deadlock when calling a per-vcpu IOCTL over a foreign context: calling thread holds qemu_mutex and blocks on kvm_mutex inside the kernel, target vcpu is running endless guest loop, holding kvm_mutex, all other qemu threads will sooner or later block on the global lock. That's at least one pattern you can get on x86 (we had a few of such bugs in the past). Jan --------------enigF03A454143EB509360DB9FDA Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.15 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org/ iEYEARECAAYFAk3rwXgACgkQitSsb3rl5xRHLACePu5bcSEOEB2gXsTcEhq1AHZr W6IAoJqkE+nZsTouzgsT8VDp/TO8e6so =5fZl -----END PGP SIGNATURE----- --------------enigF03A454143EB509360DB9FDA--