From: Jan Kiszka <jan.kiszka@web.de>
To: "Maciej W. Rozycki" <macro@linux-mips.org>
Cc: Paolo Bonzini <pbonzini@redhat.com>,
Matthew Ogilvie <mmogilvi_qemu@miniinfo.net>,
kvm@vger.kernel.org, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH 1/2] KVM: fix i8259 interrupt high to low transition logic
Date: Tue, 11 Sep 2012 11:04:30 +0200 [thread overview]
Message-ID: <504EFE9E.3090503@web.de> (raw)
In-Reply-To: <alpine.LFD.2.00.1209110133120.8926@eddie.linux-mips.org>
[-- Attachment #1: Type: text/plain, Size: 1065 bytes --]
On 2012-09-11 02:49, Maciej W. Rozycki wrote:
> On Sun, 9 Sep 2012, Matthew Ogilvie wrote:
>
>> This bug manifested itself when the guest was Microport UNIX
>> System V/386 v2.1 (ca. 1987), because it would sometimes mask
>> off IRQ14 in the slave IMR after it had already been asserted.
>> The master would still try to deliver an interrupt even though
>> IRQ2 had dropped again, resulting in a spurious interupt
>> (IRQ15) and a panicked UNIX kernel.
>
> That is quite weird actually -- from my experience the spurious vector is
> never sent from a slave (quite understandably -- since the interrupt is
> gone and no other is pending, the master has no reason to select a slave
> to supply a vector and therefore supplies the spurious vector itself) and
> therefore a spurious IRQ7 is always issued regardless of whether the
> discarded request came from a slave or from the master.
As we do not clear IRQ14 in IRR of the slave nor do we clear IRQ2 of the
master, the master has a good reason to ask the slave for the vector.
Jan
[-- Attachment #2: OpenPGP digital signature --]
[-- Type: application/pgp-signature, Size: 259 bytes --]
next prev parent reply other threads:[~2012-09-11 9:05 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-10 1:29 [Qemu-devel] [PATCH 1/2] KVM: fix i8259 interrupt high to low transition logic Matthew Ogilvie
2012-09-10 1:29 ` [Qemu-devel] [PATCH 2/2] KVM: i8259: refactor pic_set_irq level logic Matthew Ogilvie
2012-09-11 0:49 ` [Qemu-devel] [PATCH 1/2] KVM: fix i8259 interrupt high to low transition logic Maciej W. Rozycki
2012-09-11 4:54 ` Matthew Ogilvie
2012-09-11 11:53 ` Maciej W. Rozycki
2012-09-11 9:04 ` Jan Kiszka [this message]
2012-09-12 8:01 ` Avi Kivity
2012-09-12 8:48 ` Jan Kiszka
2012-09-12 8:51 ` Avi Kivity
2012-09-12 8:57 ` Jan Kiszka
2012-09-12 9:02 ` Avi Kivity
2012-09-13 5:49 ` Matthew Ogilvie
2012-09-13 13:41 ` Maciej W. Rozycki
2012-09-13 13:49 ` Jan Kiszka
2012-09-13 13:55 ` Jan Kiszka
2012-09-13 15:48 ` Maciej W. Rozycki
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=504EFE9E.3090503@web.de \
--to=jan.kiszka@web.de \
--cc=kvm@vger.kernel.org \
--cc=macro@linux-mips.org \
--cc=mmogilvi_qemu@miniinfo.net \
--cc=pbonzini@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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).