linux-kernel - Re: [PATCH] smp/call: Detect stuck CSD locks

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Message-ID: <20150520181945.GA20853@canonical.com>
Date:	Wed, 20 May 2015 11:19:45 -0700
From:	Chris J Arges <chris.j.arges@...onical.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rafael David Tinoco <inaddy@...ntu.com>,
	Peter Anvin <hpa@...or.com>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Jens Axboe <axboe@...nel.dk>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Gema Gomez <gema.gomez-solano@...onical.com>,
	the arch/x86 maintainers <x86@...nel.org>
Subject: Re: [PATCH] smp/call: Detect stuck CSD locks

On Mon, May 11, 2015 at 04:00:03PM +0200, Ingo Molnar wrote:
> > So potentially, CPU0 generated an interrupt that caused 
> > vcpu_enter_guest to be called on CPU1. However, when 
> > vmx_handle_external_intr was called, it didn't progress any further.
> 
> So the IPI does look like to be lost in the KVM code?
> 
> So why did vmx_handle_external_intr() skip the irq injection - were 
> IRQs disabled in the guest perhaps?
> 
> > Another experiment here would be to dump 
> > vmcs_read32(VM_EXIT_INTR_INFO); to see why we don't handle the 
> > interrupt.
> 
> Possibly, but also to instrument the KVM IRQ injection code to see 
> when it skips an IPI and why.
> 
> Thanks,
> 
> 	Ingo
>

Ingo,
I no longer have access to the reproducer machine unfortunately. I'll try to
locate additional kit that has the same situation, but it may take some time.
Thanks,
--chris
 
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