linux-kernel - Re: [PATCH 0/3] x86: clear vmcss on all cpus when doing kdump if necessary

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Date:	Mon, 15 Oct 2012 17:43:20 +0200
From:	Avi Kivity <avi@...hat.com>
To:	Zhang Yanfei <zhangyanfei@...fujitsu.com>
CC:	x86@...nel.org, kexec@...ts.infradead.org,
	linux-doc@...r.kernel.org, mtosatti@...hat.com,
	linux-kernel@...r.kernel.org,
	"kvm@...r.kernel.org" <kvm@...r.kernel.org>
Subject: Re: [PATCH 0/3] x86: clear vmcss on all cpus when doing kdump if
 necessary

On 10/12/2012 08:40 AM, Zhang Yanfei wrote:
> Currently, kdump just makes all the logical processors leave VMX operation by
> executing VMXOFF instruction, so any VMCSs active on the logical processors may
> be corrupted. But, sometimes, we need the VMCSs to debug guest images contained
> in the host vmcore. To prevent the corruption, we should VMCLEAR the VMCSs before
> executing the VMXOFF instruction.

How have you verified that VMXOFF doesn't flush cached VMCSs already?

> 
> The patch set provides an alternative way to clear VMCSs related to guests
> on all cpus when host is doing kdump.
> 

I'm not sure the sysctl is really necessary.  The only reason to turn if
off is if the corruption is so severe that the loaded vmcs list itself
causes a crash.  I think it should be rare enough that we can do it
unconditionally.

-- 
error compiling committee.c: too many arguments to function
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