From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:60806) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TBMOr-00048n-VQ for qemu-devel@nongnu.org; Tue, 11 Sep 2012 05:05:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TBMOn-0004RA-ST for qemu-devel@nongnu.org; Tue, 11 Sep 2012 05:04:53 -0400 Received: from mout.web.de ([212.227.17.12]:62420) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TBMOn-0004Qr-J4 for qemu-devel@nongnu.org; Tue, 11 Sep 2012 05:04:49 -0400 Message-ID: <504EFE9E.3090503@web.de> Date: Tue, 11 Sep 2012 11:04:30 +0200 From: Jan Kiszka MIME-Version: 1.0 References: <1347240563-6212-1-git-send-email-mmogilvi_qemu@miniinfo.net> In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig2B12FCC9E316EC197DA8AB61" Subject: Re: [Qemu-devel] [PATCH 1/2] KVM: fix i8259 interrupt high to low transition logic List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Maciej W. Rozycki" Cc: Paolo Bonzini , Matthew Ogilvie , kvm@vger.kernel.org, qemu-devel@nongnu.org This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig2B12FCC9E316EC197DA8AB61 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 2012-09-11 02:49, Maciej W. Rozycki wrote: > On Sun, 9 Sep 2012, Matthew Ogilvie wrote: >=20 >> This bug manifested itself when the guest was Microport UNIX >> System V/386 v2.1 (ca. 1987), because it would sometimes mask >> off IRQ14 in the slave IMR after it had already been asserted. >> The master would still try to deliver an interrupt even though >> IRQ2 had dropped again, resulting in a spurious interupt >> (IRQ15) and a panicked UNIX kernel. >=20 > That is quite weird actually -- from my experience the spurious vector= is=20 > never sent from a slave (quite understandably -- since the interrupt is= =20 > gone and no other is pending, the master has no reason to select a slav= e=20 > to supply a vector and therefore supplies the spurious vector itself) a= nd=20 > therefore a spurious IRQ7 is always issued regardless of whether the=20 > discarded request came from a slave or from the master. As we do not clear IRQ14 in IRR of the slave nor do we clear IRQ2 of the master, the master has a good reason to ask the slave for the vector. Jan --------------enig2B12FCC9E316EC197DA8AB61 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://www.enigmail.net/ iEYEARECAAYFAlBO/p4ACgkQitSsb3rl5xReMQCfbNj0CGoQ9dtjRIHfqNy8v545 7y4AnApRyDvG3H1/9Gqor6DIBjnrF4AA =6mTd -----END PGP SIGNATURE----- --------------enig2B12FCC9E316EC197DA8AB61--