linux-kernel - Re: is kexec on Xen domU possible?

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Message-ID: <51E9A85D.2060206@zytor.com>
Date:	Fri, 19 Jul 2013 13:58:05 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	Daniel Kiper <daniel.kiper@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Eric Biederman <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org, Brandon Philips <brandon@...p.org>,
	xen-devel@...ts.xensource.com,
	virtualization@...ts.linux-foundation.org
Subject: Re: is kexec on Xen domU possible?

On 07/19/2013 12:14 PM, Greg KH wrote:
>>
>>> The errors that the kexec tools seem to run into is finding the memory
>>> to place the new kernel into, is that just an issue that PV guests
>>> aren't given enough kernel memory in which to replicate themselves from
>>> dom0?
>>
>> There are a lot of differences between baremetal machines and PV guests.
>> For example you are not able to do identity mapping per se in PV guests.
>> Arguments to new kernel are passed in completely different way. etc.
> 
> Ok, thanks for confirming that it is possible, but doesn't currently
> work for pv guests.
> 

Also, in any virtualized environment the hypervisor can do a better job
for things like kdump, simply because it can provide two things that are
otherwise hard to do:

1. a known-good system state;
2. a known-clean kdump image.

As such, I do encourage the virtualization people to (also) develop
hypervisor-*aware* solutions for these kinds of things.

	-hpa


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