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From: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
To: Jan Beulich <JBeulich@suse.com>, daniel.kiper@oracle.com
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
	Wei Liu <Wei.Liu2@citrix.com>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>
Subject: Re: Request to revert superpage adjustments
Date: Fri, 11 Mar 2016 09:35:19 -0500	[thread overview]
Message-ID: <20160311143518.GA5133@char.us.oracle.com> (raw)
In-Reply-To: <56E2E09302000078000DBA12@prv-mh.provo.novell.com>

> >>  Nor would
> >> that deal with avoiding reserved regions not too far above 1Mb,
> >> since at best the main payload can be relocatable (but certainly
> >> not the binary seen by the boot loader, as at least multiboot1
> >> doesn't support anything like that).
> > 
> > The only reason Xen sits at the 1MB boundary is because of its ELF header.
> > 
> > A plain binary with a multiboot header has no such restriction, although
> > we flag an interested to have 4k alignment using the multiboot flags. 
> > There is no technical limitation causing Xen to be linked to run at 1MB;
> > its just the way its alway been.  There is nothing preventing the entry
> > point becoming properly relocatable.

And one can make it be at 2MB - which is what Daniel's patches did.
(CC-ing Daniel in case I got it wrong). We also needed GRUB2 patches
to take into account relocating Xen at a different location.

> 
> Without proper container format, how would the boot loader
> know where to place the binary, or how to relocate it if it doesn't
> get placed at its linked address? The only alternatives I see in
> grub1 are a.out and a kludge of a.out, both of which - at the first
> glance - also don't appear to do any relocation. And for the Linux
> variant, as said, it doesn't look like it's compatible with us needing
> multiple modules.
> 
> Jan
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel

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  reply	other threads:[~2016-03-11 14:35 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-11  9:22 Request to revert superpage adjustments Andrew Cooper
2016-03-11 12:06 ` Jan Beulich
2016-03-11 13:21   ` Andrew Cooper
2016-03-11 14:13     ` Jan Beulich
2016-03-11 14:35       ` Konrad Rzeszutek Wilk [this message]
2016-03-11 18:10         ` Daniel Kiper
2016-03-11 14:44       ` Andrew Cooper

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