From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: arm: warning at virt/kvm/arm/vgic.c:1468 Date: Sun, 15 Feb 2015 17:10:57 +0100 Message-ID: <54E0C511.5010008@web.de> References: <20150213044613.GA47577@lvm> <87k2zms4ub.fsf@linaro.org> <87iof6s3o7.fsf@linaro.org> <54E05E8A.5020109@web.de> <87wq3je1o4.fsf@why.wild-wind.fr.eu.org> <54E0AFE8.20202@web.de> <87oaovdxvb.fsf@why.wild-wind.fr.eu.org> <54E0B646.6030601@web.de> <87k2zjdwg4.fsf@why.wild-wind.fr.eu.org> <54E0BCB2.9000103@web.de> <20150215155954.GC8034@cbox> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="nT4BfEQuteDMAOMpQucj0MDeMxl6QoEfW" Cc: Marc Zyngier , =?windows-1252?Q?Alex_Benn=E9e?= , kvmarm , kvm , Paolo Bonzini , Wei Huang To: Christoffer Dall Return-path: Received: from mout.web.de ([212.227.15.3]:64173 "EHLO mout.web.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754863AbbBOQLI (ORCPT ); Sun, 15 Feb 2015 11:11:08 -0500 In-Reply-To: <20150215155954.GC8034@cbox> Sender: kvm-owner@vger.kernel.org List-ID: This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --nT4BfEQuteDMAOMpQucj0MDeMxl6QoEfW Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: quoted-printable On 2015-02-15 16:59, Christoffer Dall wrote: > On Sun, Feb 15, 2015 at 04:35:14PM +0100, Jan Kiszka wrote: >> On 2015-02-15 16:30, Marc Zyngier wrote: >>> On Sun, Feb 15 2015 at 3:07:50 pm GMT, Jan Kiszka wrote: >>>> On 2015-02-15 15:59, Marc Zyngier wrote: >>>>> On Sun, Feb 15 2015 at 2:40:40 pm GMT, Jan Kiszka wrote: >>>>>> On 2015-02-15 14:37, Marc Zyngier wrote: >>>>>>> On Sun, Feb 15 2015 at 8:53:30 am GMT, Jan Kiszka >>>>>>> wrote: >>>>>>>> I'm now throwing trace_printk at my broken KVM. Already found ou= t that I >>>>>>>> get ARM_EXCEPTION_IRQ every few 10 =B5s. Not seeing any irq_* tr= aces, >>>>>>>> though. Weird. >>>>>>> >>>>>>> This very much looks like a screaming interrupt. At such a rate, = no >>>>>>> wonder your VM make much progress. Can you find out which interru= pt is >>>>>>> screaming like this? Looking at GICC_HPPIR should help, but you'l= l have >>>>>>> to map the CPU interface in HYP before being able to access it th= ere. >>>>>> >>>>>> OK... let me figure this out. I had this suspect as well - the hos= t gets >>>>>> a VM exit for each injected guest IRQ? >>>>> >>>>> Not exactly. There is a VM exit for each physical interrupt that fi= res >>>>> while the guest is running. Injecting an interrupt also causes a VM= >>>>> exit, as we force the vcpu to reload its context. >>>> >>>> Ah, GICC !=3D GICV - you are referring to host-side pending IRQs. An= y >>>> hints on how to get access to that register would accelerate the >>>> analysis (ARM KVM code is still new to me). >>> >>> Map the GICC region in HYP using create_hyp_io_mapping (see >>> vgic_v2_probe for an example of how we map GICH), and stash the read = of >>> GICC_HPPIR before leaving HYP mode (and before saving the guest timer= ). >> >> OK. >> >>> >>> BTW, when you look at /proc/interrupts on the host, don't you see an >>> interrupt that's a bit too eager to fire? >> >> No - but that makes sense given that we do not enter any interrupt >> handler according to ftrace, thus there can't be any counter increment= ation. >> >>> >>>>>> BTW, I also tried with in-kernel GIC disabled (in the kernel confi= g), >>>>>> but I guess that's pointless. Linux seems to be stuck on a >>>>>> non-functional architectural timer then, right? >>>>> >>>>> Yes. Useful for bringup, but nothing more. >>>> >>>> Maybe we should perform a feature check and issue a warning from QEM= U? >>> >>> I'd assume this is already in place (but I almost never run QEMU, so = I >>> could be wrong here). >> >> Nope, QEMU starts up fine, just lets the guest starve while waiting fo= r >> jiffies to increase. >> >=20 > you should be able to turn the in-kernel irqchip off with a QEMU > command-line option and the that should prevent the kernel from adding > an arch-timer. This would only work on the vexpress guest model though= , > since the virt-board doesn't provide an emulated timer as a replacement= =2E I'm running vexpress, but I only tried legacy -no-kvm-irqchip so far which was refused. -machine vexpress-a15,kernel_irqchip=3Doff has an effect: host practically locks up, dmesg - when I'm still able to start on a different console - gives endless "Unexpected interrupt 19 on vcpu ecd39670". Well, a different smell, but still very fishy. Jan --nT4BfEQuteDMAOMpQucj0MDeMxl6QoEfW 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 iEYEARECAAYFAlTgxREACgkQitSsb3rl5xT/pwCg1M2spk1h8q8WJ9zkgwakmPj6 D1gAnjulhrxsz2WNh2e5T7N+SV7kvQUj =7eew -----END PGP SIGNATURE----- --nT4BfEQuteDMAOMpQucj0MDeMxl6QoEfW--