From: Jan Kiszka <jan.kiszka@web.de>
To: "Maciej W. Rozycki" <macro@linux-mips.org>
Cc: Matthew Ogilvie <mmogilvi_qemu@miniinfo.net>,
qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>,
kvm@vger.kernel.org
Subject: Re: [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>
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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
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WARNING: multiple messages have this Message-ID (diff)
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>
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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
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next prev parent reply other threads:[~2012-09-11 9:04 UTC|newest]
Thread overview: 32+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-10 1:29 [PATCH 1/2] KVM: fix i8259 interrupt high to low transition logic Matthew Ogilvie
2012-09-10 1:29 ` [Qemu-devel] " Matthew Ogilvie
2012-09-10 1:29 ` [PATCH 2/2] KVM: i8259: refactor pic_set_irq level logic Matthew Ogilvie
2012-09-10 1:29 ` [Qemu-devel] " Matthew Ogilvie
2012-09-11 0:49 ` [PATCH 1/2] KVM: fix i8259 interrupt high to low transition logic Maciej W. Rozycki
2012-09-11 0:49 ` [Qemu-devel] " Maciej W. Rozycki
2012-09-11 4:54 ` Matthew Ogilvie
2012-09-11 4:54 ` [Qemu-devel] " Matthew Ogilvie
2012-09-11 11:53 ` Maciej W. Rozycki
2012-09-11 11:53 ` [Qemu-devel] " Maciej W. Rozycki
2012-09-11 9:04 ` Jan Kiszka [this message]
2012-09-11 9:04 ` Jan Kiszka
2012-09-12 8:01 ` Avi Kivity
2012-09-12 8:01 ` Avi Kivity
2012-09-12 8:48 ` Jan Kiszka
2012-09-12 8:48 ` [Qemu-devel] " Jan Kiszka
2012-09-12 8:51 ` Avi Kivity
2012-09-12 8:51 ` [Qemu-devel] " Avi Kivity
2012-09-12 8:57 ` Jan Kiszka
2012-09-12 8:57 ` Jan Kiszka
2012-09-12 9:02 ` Avi Kivity
2012-09-12 9:02 ` Avi Kivity
2012-09-13 5:49 ` Matthew Ogilvie
2012-09-13 5:49 ` [Qemu-devel] " Matthew Ogilvie
2012-09-13 13:41 ` Maciej W. Rozycki
2012-09-13 13:41 ` Maciej W. Rozycki
2012-09-13 13:49 ` Jan Kiszka
2012-09-13 13:49 ` Jan Kiszka
2012-09-13 13:55 ` Jan Kiszka
2012-09-13 13:55 ` Jan Kiszka
2012-09-13 15:48 ` Maciej W. Rozycki
2012-09-13 15:48 ` Maciej W. Rozycki
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