linux-kernel - Re: [PATCH 0/4] Export offsets of VMCS fields as note information for kdump

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Date:	Thu, 19 Apr 2012 13:42:42 +0300
From:	Avi Kivity <avi@...hat.com>
To:	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>
CC:	zhangyanfei@...fujitsu.com, mtosatti@...hat.com,
	ebiederm@...ssion.com, luto@....edu, joerg.roedel@....com,
	dzickus@...hat.com, paul.gortmaker@...driver.com, gregkh@...e.de,
	ludwig.nussel@...e.de, linux-kernel@...r.kernel.org,
	kvm@...r.kernel.org, kexec@...ts.infradead.org
Subject: Re: [PATCH 0/4] Export offsets of VMCS fields as note information
 for kdump

On 04/19/2012 01:36 PM, HATAYAMA Daisuke wrote:
> From: Avi Kivity <avi@...hat.com>
> Subject: Re: [PATCH 0/4] Export offsets of VMCS fields as note information for kdump
> Date: Wed, 18 Apr 2012 14:56:39 +0300
>
> > On 04/18/2012 12:49 PM, zhangyanfei wrote:
> >> >>
> >> > 
> >> > What type of resource?  Can you give an example?
> >> > 
> >> Sorry. No concrete example for now.
> >>
> >> We are developing this on a conservative policy and I have put the vmcs processing
> >> in a new module in patch set v2 as you required. The new module is auto-loaded when
> >> the vmx cpufeature is detected and it depends on module kvm-intel. Loading and unloading
> >> this module will have no side effect on the running guests.
> >>
> >> And one thing I have to stress is that, we can see guest image as crash dump from
> >> guest machine's view if we have the vmcsinfo, this itself is useful.
> > 
> > Why is it useful?  Without a concrete example, it's hard to justify the
> > code bloat.
> > 
>
> The reason why we want to retrieve guest machine's memory image as
> crash dump is that then we can debug guest machine's status using
> symbolic debugger such as gdb and crash utility.
>
> This is very useful. Please consider the situation where engineers are
> forced to look into guest machine's memory image through qemu-kvm's
> process core dump using gdb without any symbolic information. It's
> very inefficient.

I still don't follow.  If qemu crashed, the values in guest registers
are irrelevant.  In what way can the help debug the qemu crash?

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

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