From: Don Zickus <dzickus@redhat.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: x86@kernel.org, kexec-list <kexec@lists.infradead.org>,
LKML <linux-kernel@vger.kernel.org>,
vgoyal@redhat.com
Subject: Re: [PATCH] x86, kdump, ioapic: Fix kdump race with migrating irq
Date: Thu, 2 Feb 2012 10:33:20 -0500 [thread overview]
Message-ID: <20120202153320.GM5650@redhat.com> (raw)
In-Reply-To: <m1ehuevx12.fsf@fess.ebiederm.org>
On Wed, Feb 01, 2012 at 05:34:01PM -0800, Eric W. Biederman wrote:
> > Talking to folks here and trying to read the code it seems like the PIT
> > stuff is delayed until after the IOAPIC is configured using Fast TSC
> > calibration as a mechanism to work around the PIT??
> >
> > I attached the output of the Pentium4 when kdumping. Not sure what to
> > really look for to verify the PIC is being skipped. Perhaps you know?
>
> The important part is the kexec on panic works without shutting down
> the ioapic. There should be no corner case issues it should either
> work it should fail.
>
> The problem used to be that we always would initialize the PIT interrupt
> in the 8259 interrupt controller before we would initialize the ioapics
> and that would kill the boot.
>
> If I have read your testing correctly you are apparently booting in the
> kexec on panic case. That seems to be successful to me. So we should
> be able to just remove the ioapic shutdown code from
> machine_crash_shutdown as it is no longer needed.
>
> Thank you for being careful and testing on a number of different
> platforms.
No problem. I was actually trying to find machines that did not have
ioapics to make sure they still worked (it's hard!).
So if I test on a couple more machines (hopefully one without an ioapic),
can I get your ack? Or is there something else you would like me to do to
verify things are working correctly?
I will also need your help writing the changelog such that people
understand why removing that line is safe now.
>
> The only case I can think that won't work without ioapic disables
> is using a crash kernel that doesn't emable the ioapics.
Ok. I can see that. Would you agree that scenario is not a very sane
case? :-) Does not using the ioapic really save you anything?
Otherwise the alternative is to use my original patch.
Thanks for the help.
Cheers,
Don
>
> Eric
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WARNING: multiple messages have this Message-ID (diff)
From: Don Zickus <dzickus@redhat.com>
To: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: x86@kernel.org, LKML <linux-kernel@vger.kernel.org>,
vgoyal@redhat.com, kexec-list <kexec@lists.infradead.org>
Subject: Re: [PATCH] x86, kdump, ioapic: Fix kdump race with migrating irq
Date: Thu, 2 Feb 2012 10:33:20 -0500 [thread overview]
Message-ID: <20120202153320.GM5650@redhat.com> (raw)
In-Reply-To: <m1ehuevx12.fsf@fess.ebiederm.org>
On Wed, Feb 01, 2012 at 05:34:01PM -0800, Eric W. Biederman wrote:
> > Talking to folks here and trying to read the code it seems like the PIT
> > stuff is delayed until after the IOAPIC is configured using Fast TSC
> > calibration as a mechanism to work around the PIT??
> >
> > I attached the output of the Pentium4 when kdumping. Not sure what to
> > really look for to verify the PIC is being skipped. Perhaps you know?
>
> The important part is the kexec on panic works without shutting down
> the ioapic. There should be no corner case issues it should either
> work it should fail.
>
> The problem used to be that we always would initialize the PIT interrupt
> in the 8259 interrupt controller before we would initialize the ioapics
> and that would kill the boot.
>
> If I have read your testing correctly you are apparently booting in the
> kexec on panic case. That seems to be successful to me. So we should
> be able to just remove the ioapic shutdown code from
> machine_crash_shutdown as it is no longer needed.
>
> Thank you for being careful and testing on a number of different
> platforms.
No problem. I was actually trying to find machines that did not have
ioapics to make sure they still worked (it's hard!).
So if I test on a couple more machines (hopefully one without an ioapic),
can I get your ack? Or is there something else you would like me to do to
verify things are working correctly?
I will also need your help writing the changelog such that people
understand why removing that line is safe now.
>
> The only case I can think that won't work without ioapic disables
> is using a crash kernel that doesn't emable the ioapics.
Ok. I can see that. Would you agree that scenario is not a very sane
case? :-) Does not using the ioapic really save you anything?
Otherwise the alternative is to use my original patch.
Thanks for the help.
Cheers,
Don
>
> Eric
next prev parent reply other threads:[~2012-02-02 15:33 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-31 21:25 [PATCH] x86, kdump, ioapic: Fix kdump race with migrating irq Don Zickus
2012-01-31 21:25 ` Don Zickus
2012-01-31 21:37 ` Vivek Goyal
2012-01-31 21:37 ` Vivek Goyal
2012-01-31 22:08 ` Eric W. Biederman
2012-01-31 22:08 ` Eric W. Biederman
2012-01-31 22:27 ` Don Zickus
2012-01-31 22:27 ` Don Zickus
2012-01-31 22:38 ` Eric W. Biederman
2012-01-31 22:38 ` Eric W. Biederman
2012-02-01 23:04 ` Don Zickus
2012-02-01 23:04 ` Don Zickus
2012-02-02 1:34 ` Eric W. Biederman
2012-02-02 1:34 ` Eric W. Biederman
2012-02-02 15:33 ` Don Zickus [this message]
2012-02-02 15:33 ` Don Zickus
2012-02-02 17:45 ` Don Zickus
2012-02-02 17:45 ` Don Zickus
2012-02-20 15:20 ` Seiji Aguchi
2012-02-20 15:20 ` Seiji Aguchi
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