linux-kernel - Re: [Xen-devel] [PATCH v2 02/11] xen/hvmlite: Bootstrap HVMlite guest

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Message-ID: <56B268A2.5000704@citrix.com>
Date:	Wed, 3 Feb 2016 20:52:50 +0000
From:	Andrew Cooper <andrew.cooper3@...rix.com>
To:	"Luis R. Rodriguez" <mcgrof@...nel.org>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
CC:	<pmonclus@...mgrid.com>, <GLin@...e.coma>, <mcgrof@...e.com>,
	<x86@...nel.org>, <linux-kernel@...r.kernel.org>,
	David Vrabel <david.vrabel@...rix.com>, <hpa@...or.com>,
	<xen-devel@...ts.xenproject.org>, <bp@...e.de>,
	<bblanco@...mgrid.com>, <roger.pau@...rix.com>
Subject: Re: [Xen-devel] [PATCH v2 02/11] xen/hvmlite: Bootstrap HVMlite guest

On 03/02/16 18:55, Luis R. Rodriguez wrote:
> We add new hypervisor type to close the semantic gap for hypervisor types, and
> much like subarch enable also a subarch_data to let you pass and use your
> hvmlite_start_info. This would not only help with the semantics but also help
> avoid yet-another-entry point and force us to provide a well define structure
> for considering code that should not run by pegging it as required or supported
> for different early x86 code stubs.

Was I unclear last time?  Xen *will not* be introducing Linux-specifics
into the HVMLite starting ABI.

Your perceived problem with multiple entry points is not a problem with
multiple entry points; It is a problem with multiple different paths
performing the same initialisation.

The Linux entry for PV guests is indeed completely horrible.  I am not
trying to defend it in the slightest.

However, the HVMLite entry which is a very short stub that sets up a
zeropage and hands off to the native start routine is fine.  There is
still just routine performing native x86 startup.

If you still desperately want to avoid multiple entry points, then just
insist on using grub for the VM.  I expect that that is how most people
will end up using HVMLite VMs anyway.

~Andrew