linux-kernel - Re: [Xen-devel] incorrect layout of globals from head

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Date:	Tue, 10 Jul 2012 09:29:09 -0600
From:	Ian Campbell <ian.campbell@...rix.com>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
CC:	Olaf Hering <olaf@...fle.de>, Daniel Kiper <dkiper@...-space.pl>,
	"xen-devel@...ts.xensource.com" <xen-devel@...ts.xensource.com>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Jan Beulich <JBeulich@...e.com>
Subject: Re: [Xen-devel] incorrect layout of globals from head_64.S during
 kexec boot

On Tue, 2012-07-10 at 10:51 -0400, Konrad Rzeszutek Wilk wrote:
> On Tue, Jul 10, 2012 at 08:46:34AM -0600, Ian Campbell wrote:
> > On Tue, 2012-07-10 at 10:14 -0400, Konrad Rzeszutek Wilk wrote:
> > > Which brings me to another question - say we do use this patch, what
> > > if the decompressor overwrites the old kernels .data section. Won't
> > > we run into this problem again?
> > 
> > I've not really been following this thread that closely but wouldn't the
> > right answer be for the original kernel to unmap the shared info on
> > kexec? Or maybe remap it up to some high/reserved address? Can it read
> 
> That would be the right answer I think, but I don't see the a VCPU_deregister
> call (only VCPU_register).

Is the issue here vcpuinfo or the shared info (or both)?

> But perhaps the XENMEM_decrease_reservation for the particular MFN is the
> answer to do a VCPU "de-register" ?
> 
> > the original address used by hvmloader at start of day and reuse that?
> 
> Wait, we can map multiple shared_info? Ooh, somehow I thought the guest
> could only do one registration.

I think you can only have one mapping but you can move it by registering
it again.

Ian.


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