Re: [PATCH 05/15] Coalesce userspace/kernel irqchip interrupt injection logic.

From: Jan Kiszka <jan.kiszka@siemens.com>
To: Gleb Natapov <gleb@redhat.com>
Cc: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>, kvm@vger.kernel.org
Subject: Re: [PATCH 05/15] Coalesce userspace/kernel irqchip interrupt	injection logic.
Date: Wed, 15 Apr 2009 12:51:00 +0200	[thread overview]
Message-ID: <49E5BC14.6070703@siemens.com> (raw)
In-Reply-To: <20090415103648.GD27675@redhat.com>

Gleb Natapov wrote:
> On Wed, Apr 15, 2009 at 12:22:34PM +0200, Jan Kiszka wrote:
>> Gleb Natapov wrote:
>>> On Wed, Apr 15, 2009 at 01:30:29PM +0400, Dmitry Eremin-Solenikov wrote:
>>>> 2009/4/14 Gleb Natapov <gleb@redhat.com>:
>>>>> On Tue, Apr 14, 2009 at 11:29:49PM +0400, Dmitry Eremin-Solenikov wrote:
>>>>>> 2009/4/14 Gleb Natapov <gleb@redhat.com>:
>>>>>>> On Tue, Apr 14, 2009 at 06:32:29PM +0400, Dmitry Eremin-Solenikov wrote:
>>>>>>>> 2009/4/14 Gleb Natapov <gleb@redhat.com>:
>>>>>>>>> On Tue, Apr 14, 2009 at 02:14:04PM +0000, Dmitry Eremin-Solenikov wrote:
>>>>>>>>>> Gleb Natapov wrote:
>>>>>>>>>>
>>>>>>>>>>> Start to use interrupt/exception queues like VMX does. This also fix the
>>>>>>>>>>> bug that if exit was caused by a guest internal exception access to IDT
>>>>>>>>>>> the exception was not reinjected.
>>>>>>>>>> This patch broke KVM for me: after it is applied (to the tip of avi's git tree),
>>>>>>>>>> linux inside KVM (version 84 from Debian) stops booting, moaning about lost
>>>>>>>>>> interrupts from ide. The KVM is executed inside qemu-system-x86_64,
>>>>>>>>>> version 0.10.2.
>>>>>>>>>>
>>>>>>>>> Please apply next patch in the series too. This one will not work
>>>>>>>>> without it. But better yet can you please test entire series.
>>>>>>>> After applying the next patch (or the whole serie), I get the following messages
>>>>>>>> during initramfs drivers probe:
>>>>>>>>
>>>>>>>> Clocksource tsc unstable (delta...)
>>>>>>>> no cont in shutdown!
>>>>>>>> floppy0: FDC access conflict!
>>>>>>>>
>>>>>>>> Then kernel boot stalls. I'll try gdbing into kernel but this may
>>>>>>>> require lots of efforts.
>>>>>>>> I don't quite understand how do these two patches influence FDC emulation, but
>>>>>>>> they do. Tell me if you need any additional info.
>>>>>>>>
>>>>>>> What guest is this? What kernel? Does the whole series works?
>>>>>> Guest: Debian lenny. Linux 2.6.26, Debian version (I can provide
>>>>>> config or bzImage + initrd).
>>>>> Yes please provide. Debian lenny (x86_64) is my default guest :) And I
>>>>> just booted it fine on AMD barcelona CPU.  What is you host cpu?
>>>>> "cat /proc/cpuinfo"
>>>> qemu-x86_64 version 0.10.2 running on i386
>>>> Due to problems with qemu-x86_64 I have to boot the 'host' kernel with 'noapic'.
>>>> qemu-64:~# cat /proc/cpuinfo
>>>> processor       : 0
>>>> vendor_id       : AuthenticAMD
>>>> cpu family      : 6
>>>> model           : 2
>>>> model name      : QEMU Virtual CPU version 0.10.2
>>>> stepping        : 3
>>>> cpu MHz         : 1828.754
>>>> cache size      : 512 KB
>>>> fpu             : yes
>>>> fpu_exception   : yes
>>>> cpuid level     : 2
>>>> wp              : yes
>>>> flags           : fpu de pse tsc msr pae mce cx8 apic sep mtrr pge mca
>>>> cmov pat pse36 clflush mmx fxsr sse sse2 syscall nx lm 3dnowext 3dnow
>>>> up pni svm
>>>> bogomips        : 3700.32
>>>> TLB size        : 1024 4K pages
>>>> clflush size    : 64
>>>> cache_alignment : 64
>>>> address sizes   : 40 bits physical, 48 bits virtual
>>>> power management:
>>>>
>>>>
>>> I need _host_ cpu info. Do the same on the host please.
>> That _is_ his host - qemu in emulation mode (ie. nested virtualization).
> Ah, now I noticed svm in cpu flags. Does qemu support svm in TCG?

Yes, and KVM seems to have been fine without the patch. But that may not
exclude remaining bugs in QEMU (as first-level hypervisor here).

On the other hand, it wouldn't be the first time QEMU, with its extreme
delays, triggers some nasty race in its guest...

> 
>> Maybe there is an issue with qemu's emulation of svm or, rather, with
>> the apic emulation. The fact that he has to boot the first-level guest
>> with noapic is fairly suspicious.
>>
>> Dmitry, what is your first level-guest distro/kernel, also Lenny? And
>> what is the top-level qemu command line? Let's focus on this first,
>> leaving KVM and this patch series aside for a while.
>>
> If KVM runs inside a guest that is definitely a good idea :)
> 
> --
> 			Gleb.

Jan

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