linux-kernel - Re: [Xen-devel] [PATCH v3 00/11] xen: Initial kexec/kdump implementation

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Message-ID: <50E6E974.5090805@citrix.com>
Date:	Fri, 4 Jan 2013 14:38:44 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Daniel Kiper <daniel.kiper@...cle.com>
CC:	Andrew Cooper <andrew.cooper3@...rix.com>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"konrad.wilk@...cle.com" <konrad.wilk@...cle.com>,
	"maxim.uvarov@...cle.com" <maxim.uvarov@...cle.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"virtualization@...ts.linux-foundation.org" 
	<virtualization@...ts.linux-foundation.org>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	"jbeulich@...e.com" <jbeulich@...e.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	"tglx@...utronix.de" <tglx@...utronix.de>,
	"vgoyal@...hat.com" <vgoyal@...hat.com>
Subject: Re: [Xen-devel] [PATCH v3 00/11] xen: Initial kexec/kdump implementation

On 04/01/13 14:22, Daniel Kiper wrote:
> On Wed, Jan 02, 2013 at 11:26:43AM +0000, Andrew Cooper wrote:
>> On 27/12/12 18:02, Eric W. Biederman wrote:
>>> Andrew Cooper<andrew.cooper3@...rix.com>  writes:
>>>
>>>> On 27/12/2012 07:53, Eric W. Biederman wrote:
>>>>> The syscall ABI still has the wrong semantics.
>>>>>
>>>>> Aka totally unmaintainable and umergeable.
>>>>>
>>>>> The concept of domU support is also strange.  What does domU support even mean, when the dom0 support is loading a kernel to pick up Xen when Xen falls over.
>>>> There are two requirements pulling at this patch series, but I agree
>>>> that we need to clarify them.
>>> It probably make sense to split them apart a little even.
>>>
>>>
>>
>> Thinking about this split, there might be a way to simply it even more.
>>
>> /sbin/kexec can load the "Xen" crash kernel itself by issuing
>> hypercalls using /dev/xen/privcmd.  This would remove the need for
>> the dom0 kernel to distinguish between loading a crash kernel for
>> itself and loading a kernel for Xen.
>>
>> Or is this just a silly idea complicating the matter?
> 
> This is impossible with current Xen kexec/kdump interface.
> It should be changed to do that. However, I suppose that
> Xen community would not be interested in such changes.

I don't see why the hypercall ABI cannot be extended with new sub-ops
that do the right thing -- the existing ABI is a bit weird.

I plan to start prototyping something shortly (hopefully next week) for
the Xen kexec case.

David
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