From: Avi Kivity <avi@redhat.com>
To: Alexander Graf <agraf@suse.de>
Cc: Marcelo Tosatti <mtosatti@redhat.com>,
qemu-devel List <qemu-devel@nongnu.org>
Subject: [Qemu-devel] Re: [RFC] KVM: PPC: Add level based interrupt logic
Date: Wed, 01 Sep 2010 14:56:53 +0300 [thread overview]
Message-ID: <4C7E3F85.8090201@redhat.com> (raw)
In-Reply-To: <B1E5FE68-76C8-4083-8EA0-3D9762435084@suse.de>
On 09/01/2010 02:47 PM, Alexander Graf wrote:
> On 01.09.2010, at 13:45, Avi Kivity wrote:
>
>> On 09/01/2010 12:38 PM, Alexander Graf wrote:
>>> On 01.09.2010, at 09:41, Avi Kivity wrote:
>>>
>>>> On 08/31/2010 01:07 PM, Alexander Graf wrote:
>>>>> KVM on PowerPC used to have completely broken interrupt logic. Usually,
>>>>> interrupts work by having a PIC that pulls a line up/down, so the CPU knows
>>>>> that an interrupt is active. This line stays active until some action is
>>>>> done to the PIC to release the line.
>>>>>
>>>>> On KVM for PPC, we just checked if there was an interrupt pending and pulled
>>>>> a line in the kernel module. We never released it though, hoping that kernel
>>>>> space would just declare an interrupt as released when injected - which is
>>>>> wrong.
>>>>>
>>>>> To fix this, we need to completely redesign the interrupt injection logic.
>>>>> Whenever an interrupt line gets triggered, we need to notify kernel space
>>>>> that the line is up. Whenever it gets released, we do the same. This way
>>>>> we can assure that the interrupt state is always known to kernel space.
>>>>>
>>>>> This fixes random stalls in KVM guests on PowerPC that were waiting for
>>>>> an interrupt while everyone else thought they received it already.
>>>> This is more or less equivalent to KVM_IRQ_LINE.
>>> My question was if you think the internal C interface is generic enough or if it needs a lot more magic for x86 anyways :).
>>>
>> So you noticed I avoided it. Well, being forced to look, I don't think it's worthwhile to try to be generic here. Both the PIC<->APIC and the APIC<->core interfaces are too complicated to be modelled by a single line.
> Makes sense. Well, I guess it doesn't hurt to have the interface as is and only implement it for PPC for now.
>
>
Why not limit it to ppc? Someone might call it by accident.
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
next prev parent reply other threads:[~2010-09-01 11:57 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-08-31 10:07 [Qemu-devel] [RFC] KVM: PPC: Add level based interrupt logic Alexander Graf
2010-09-01 7:41 ` [Qemu-devel] " Avi Kivity
2010-09-01 9:38 ` Alexander Graf
2010-09-01 11:45 ` Avi Kivity
2010-09-01 11:47 ` Alexander Graf
2010-09-01 11:56 ` Avi Kivity [this message]
2010-09-01 11:58 ` Alexander Graf
2010-09-01 12:09 ` Avi Kivity
2010-09-01 12:09 ` Avi Kivity
2010-09-01 12:10 ` Alexander Graf
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=4C7E3F85.8090201@redhat.com \
--to=avi@redhat.com \
--cc=agraf@suse.de \
--cc=mtosatti@redhat.com \
--cc=qemu-devel@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.