From: Guenter Roeck <linux@roeck-us.net>
To: Jiang Liu <jiang.liu@linux.intel.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>,
linux-next@vger.kernel.org, linux-kernel@vger.kernel.org,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: linux-next: Tree for Nov 14
Date: Mon, 17 Nov 2014 09:02:15 -0800 [thread overview]
Message-ID: <20141117170215.GC28915@roeck-us.net> (raw)
In-Reply-To: <546983B1.6060105@linux.intel.com>
On Mon, Nov 17, 2014 at 01:12:17PM +0800, Jiang Liu wrote:
> On 2014/11/16 11:22, Guenter Roeck wrote:
> > On 11/15/2014 06:33 PM, Jiang Liu wrote:
> >> Hi Guenter,
> >> Could you please help to provide the config file and
> >> error messages?
> >
> > Config file:
> > https://github.com/groeck/linux-build-test/blob/master/rootfs/x86/qemu_x86_pc_nosmp_defconfig
> >
> >
> > Error log:
> > http://server.roeck-us.net:8010/builders/qemu-x86-next/builds/44/steps/qemubuildcommand/logs/stdio
> >
> >
> > You can find the root file system used for the test as well as the test
> > script at
> > https://github.com/groeck/linux-build-test/tree/master/rootfs/x86
> >
> > There isn't really an error message, though - the boot stalls until the
> > controlling daemon
> > kills the qemu session.
> Hi Guenter,
> With the test suite at
> https://github.com/groeck/linux-build-test/tree/master/rootfs/x86
> and configuration file qemu_x86_pc_nosmp_defconfig, I have
> following findings:
> 1) disabling PCI_MSI, <OK>.
> 2) manually turning on X86_IO_APIC, <OK>.
> 3) with 3.16 kernel, disabling PCI_MSI, <OK>
> 4) with 3.16 kernel, disabling PCI_MSI, enabling X86_UP_APIC, <fail>
>
> So the root cause is that KVM doesn't support the configuration with
> LOCAL_APIC enabled but IO_APIC disabled, though this configuration
> works with bare-metal machines.
> There are two possible solutions here:
> 1) ALways enalbe IO_APIC if KVM is enabled.
> 2) Enhance KVM to support LOCAL_APIC when IOAPIC is disabled.
>
> But I'm not familiar with KVM and don't know how to achieve solution 2.
> Any suggestions?
I don't understand KVM well enough either. For my part I don't understand why
APIC configuration in the kernel differs between the SMP and the non-SMP case
(ie why X86_IO_APIC is enabled for smp but not for non-smp). After all, the
hardware does not change. On the other side I don't have to understand it ;-).
I "solved" the problem in my test scripts by disabling PCI_MSI for the
x86/non-smp test. That doesn't really solve anything, but there is only
so much I can do.
Thanks,
Guenter
next prev parent reply other threads:[~2014-11-17 17:02 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-11-14 8:27 linux-next: Tree for Nov 14 Stephen Rothwell
2014-11-15 21:19 ` Guenter Roeck
2014-11-16 2:33 ` Jiang Liu
2014-11-16 3:22 ` Guenter Roeck
2014-11-16 4:20 ` Jiang Liu
2014-11-16 6:56 ` Guenter Roeck
2014-11-16 8:24 ` Jiang Liu
2014-11-16 8:37 ` Jiang Liu
2014-11-16 15:42 ` Guenter Roeck
2014-11-16 16:01 ` Guenter Roeck
2014-11-16 16:11 ` Guenter Roeck
2014-11-17 5:12 ` Jiang Liu
2014-11-17 17:02 ` Guenter Roeck [this message]
-- strict thread matches above, loose matches on Subject: below --
2023-11-14 3:19 Stephen Rothwell
2022-11-14 7:49 Stephen Rothwell
2019-11-14 8:31 Stephen Rothwell
2019-11-14 18:38 ` Naresh Kamboju
2019-11-14 20:11 ` Jan Stancek
2019-11-14 21:19 ` Arnd Bergmann
2018-11-14 5:26 Stephen Rothwell
2017-11-14 6:20 Stephen Rothwell
2016-11-14 7:23 Stephen Rothwell
2013-11-14 4:22 Stephen Rothwell
2012-11-14 5:30 Stephen Rothwell
2012-11-14 5:37 ` Andrew Morton
2012-11-14 5:53 ` Andrew Morton
2012-11-14 6:47 ` Ingo Molnar
2012-11-14 6:56 ` Andrew Morton
2012-11-14 7:15 ` Stephen Rothwell
2012-11-14 7:24 ` Andrew Morton
2012-11-14 7:39 ` Ingo Molnar
2012-11-14 8:13 ` Hugh Dickins
2012-11-14 17:05 ` Rik van Riel
2012-11-15 12:10 ` Mel Gorman
2012-11-14 17:19 ` Linus Torvalds
2012-11-14 6:55 ` Stephen Rothwell
2012-11-14 7:03 ` Stephen Rothwell
2011-11-14 3:43 Stephen Rothwell
2019-11-14 16:43 ` Christian Brauner
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