Date: Wed, 20 May 2015 11:19:45 -0700
From: Chris J Arges <chris.j.arges@canonical.com>
To: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
        Rafael David Tinoco <inaddy@ubuntu.com>, Peter Anvin <hpa@zytor.com>,
        Jiang Liu <jiang.liu@linux.intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        LKML <linux-kernel@vger.kernel.org>, Jens Axboe <axboe@kernel.dk>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Gema Gomez <gema.gomez-solano@canonical.com>,
        the arch/x86 maintainers <x86@kernel.org>
Subject: Re: [PATCH] smp/call: Detect stuck CSD locks
Message-ID: <20150520181945.GA20853@canonical.com>
References: <20150407205945.GA28212@canonical.com>
 <20150408064734.GA26861@gmail.com>
 <20150413035616.GA24037@canonical.com>
 <20150413061450.GA10857@gmail.com>
 <20150415195452.GA19953@canonical.com>
 <20150416110423.GA15760@gmail.com>
 <20150416155819.GA20490@canonical.com>
 <20150416163140.GA17024@gmail.com>
 <20150429210831.GA17055@canonical.com>
 <20150511140003.GA5354@gmail.com>
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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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