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

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Date:	Mon, 22 Jul 2013 19:03:07 +0200
From:	Daniel Kiper <daniel.kiper@...cle.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Greg KH <gregkh@...uxfoundation.org>,
	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 Fri, Jul 19, 2013 at 01:58:05PM -0700, H. Peter Anvin wrote:
> 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.

In general I agree but if you could not change hypervisor
and/or dom0 (e.g. you are using cloud providers which are
stick to old versions of Xen) then you have no choice.

Daniel
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