From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: 2.6.27.5 guest boot failure using in-kernel PIT Date: Fri, 21 Nov 2008 16:41:00 +0100 Message-ID: <4926D68C.8050401@web.de> References: <20081120142253.GA30825@blackpad> <20081120220517.GB30825@blackpad> <49266950.40200@web.de> <20081121131741.GC30825@blackpad> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enig3AC3A5C9346EAAEA771D92B7" Cc: kvm@vger.kernel.org To: Eduardo Habkost Return-path: Received: from fmmailgate01.web.de ([217.72.192.221]:56427 "EHLO fmmailgate01.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752642AbYKUPl5 (ORCPT ); Fri, 21 Nov 2008 10:41:57 -0500 In-Reply-To: <20081121131741.GC30825@blackpad> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enig3AC3A5C9346EAAEA771D92B7 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Eduardo Habkost wrote: > On Fri, Nov 21, 2008 at 08:54:56AM +0100, Jan Kiszka wrote: >> Eduardo Habkost wrote: >>> On Thu, Nov 20, 2008 at 12:22:53PM -0200, Eduardo Habkost wrote: >>>> Hi, >>>> >>>> When using a kvm.git kernel as host, I am getting guest boot failure= s >>>> when booting Fedora Rawhide kernel (2.6.27.5-117.fc10.x86_64). Guest= >>>> stops booting at: >>>> >>>> ENABLING IO-APIC IRQs >>>> ..TIMER: vector=3D0x30 apic1=3D0 pin1=3D0 apic2=3D-1 pin2=3D-1 >>>> ..MP-BIOS bug: 8254 timer not connected to IO-APIC >>>> ...trying to set up timer (IRQ0) through the 8259A ... >>>> ..... (found apic 0 pin 0) ... >>>> ....... failed. >>>> ...trying to set up timer as Virtual Wire IRQ... >>>> ..... failed. >>>> ...trying to set up timer as ExtINT IRQ... >>> I've just found out this problem happens because the guest has HZ=3D1= 000 >>> and the host had HZ=3D250 and no CONFIG_HIGH_RES_TIMERS. >>> >>> With this setup, the host is not managing to inject enough timer >>> interrupts during the mdelay() loop on timer_irq_works(). >>> >> Interesting, and plausible. >> >> My observation so far is a sporadic test failure, often correlating wi= th >> some raised host OS load. I'm running a high-res kernel, but that cann= ot >> prevent that this only 10 ticks long loop of the guest may obtain too >> few CPU cycles to handle enough of them once in a while (IIRC, it need= s >> 4 out of the 10 ticks to declare the timer routing functional). >> >> Maybe Gleb's anti-coalesce patches for the PIC can also deal with your= >> timer resolution conflict. At least worth a try... >=20 > Aren't Gleb patches for the userspace PIT? Yeah, they are, so you won't benefit from them for in-kernel cases. But with in-kernel emulation just the probability of coalesced ticks is a bit lower, they cannot be avoided either. > I am seeing the problem here > when using the in-kernel PIT, but (surprisingly) my setup works when > using -no-kvm-pit. Weird, makes no sense to me as well ATM. Jan --------------enig3AC3A5C9346EAAEA771D92B7 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.9 (GNU/Linux) Comment: Using GnuPG with SUSE - http://enigmail.mozdev.org iEYEARECAAYFAkkm1pQACgkQniDOoMHTA+mP6ACeIbvZQk143qkKHSnama1f3EI5 epQAnRifAekC17RQUduCAHT+6Mjkp+pE =k/c+ -----END PGP SIGNATURE----- --------------enig3AC3A5C9346EAAEA771D92B7--