linux-kernel - Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do

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Date:	Mon, 8 Feb 2016 18:44:09 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Bruce Rogers <brogers@...e.com>, kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org, Jan Kiszka <jan.kiszka@....de>
Cc:	namit@...technion.ac.il
Subject: Re: [PATCH 2/2] KVM: x86: allow BSP to handle INIT IPIs like APs do



On 08/02/2016 18:27, Bruce Rogers wrote:
> I had read that, but I though this was speaking from the perspective of the
> SMP aware BIOS code only.

It says "logical processor", so I cannot really see how it can be
interpreted that way.  The BSP jumps to 0xFFFFFFF0, the APs go into
wait-for-SIPI state.

> I certainly could be wrong about my above interpretation, but with these
> changes I'm proposing, things work well for the test case of manually onlining
> the BSP after the crash kernel has been started (via kexec -e on a AP processor
> with maxcpus=1 on the crash kernel command line). From looking through the
> kernel git history it appears this sequence of events was explicitly supported
> quite a while ago, and we've got a customer who uses this for fast recovery from
> a guest kernel crash.

You need to comment on the output of trace-cmd for KVM events, or
provide a full reproducer, or at the very least point me to the kernel
code that you're referring to.  Otherwise I just cannot understand what
you're talking about; sorry. :(

Paolo