From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH v3 5/5] KVM: Allow host IRQ sharing for passed-through PCI 2.3 devices Date: Wed, 03 Nov 2010 10:15:59 +0100 Message-ID: <4CD1284F.7070003@web.de> References: <628f014fb1efb8e2208db03d13198ba301a3a34c.1288771873.git.jan.kiszka@web.de> <20101103084320.GF6772@redhat.com> <4CD1227E.9020908@web.de> <20101103090550.GG6772@redhat.com> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigF06366643AC48A5687783C8F" Cc: Avi Kivity , Marcelo Tosatti , kvm , Alex Williamson , Jan Kiszka To: "Michael S. Tsirkin" Return-path: Received: from fmmailgate02.web.de ([217.72.192.227]:42367 "EHLO fmmailgate02.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754111Ab0KCJQL (ORCPT ); Wed, 3 Nov 2010 05:16:11 -0400 In-Reply-To: <20101103090550.GG6772@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigF06366643AC48A5687783C8F Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Am 03.11.2010 10:05, Michael S. Tsirkin wrote: > On Wed, Nov 03, 2010 at 09:51:10AM +0100, Jan Kiszka wrote: >> Am 03.11.2010 09:43, Michael S. Tsirkin wrote: >>> On Wed, Nov 03, 2010 at 09:11:16AM +0100, Jan Kiszka wrote: >>>> From: Jan Kiszka >>>> >>>> PCI 2.3 allows to generically disable IRQ sources at device level. T= his >>>> enables us to share IRQs of such devices between on the host side wh= en >>>> passing them to a guest. This feature is optional, user space has to= >>>> request it explicitly. >>>> >>>> Signed-off-by: Jan Kiszka >>> >>> >>> I just realized something. >>> With this patch, if guest ever looks at >>> interrupt disable bit, it will go crazy as that bit goes on/off by >>> itself. I guess we could have an ioctl to set/clear the bit on >>> device, and have qemu call that on config write into command/status >>> register. >> >> I understand the problem, but I don't get why the kernel should bother= =2E >> User space has to filter the config space access, returning precisely >> the value of the INTx disabled bit that the guest wrote. >=20 > Yes but if guest disables INTx it should not get interrupts :) Right, got this meanwhile. KVM-in-KVM with nested device assignment would break otherwise - intolerable. :) Jan --------------enigF06366643AC48A5687783C8F 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/ iEYEARECAAYFAkzRKFkACgkQitSsb3rl5xSKLQCdEPvbMGclu6TJfOboP7kisiI5 bk8Anir5KLMA9I0tkN5k03ASdBUDIqf8 =//2B -----END PGP SIGNATURE----- --------------enigF06366643AC48A5687783C8F--