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[Xen-devel] Re: [RFC, PATCH 2/24] i386 Vmi config

To: Christoph Hellwig <hch@xxxxxxxxxxxxx>, Zachary Amsden <zach@xxxxxxxxxx>, Linus Torvalds <torvalds@xxxxxxxx>, Linux Kernel Mailing List <linux-kernel@xxxxxxxxxxxxxxx>, Virtualization Mailing List <virtualization@xxxxxxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxx>, Dan Hecht <dhecht@xxxxxxxxxx>, Dan Arai <arai@xxxxxxxxxx>, Anne Holler <anne@xxxxxxxxxx>, Pratap Subrahmanyam <pratap@xxxxxxxxxx>, Christopher Li <chrisl@xxxxxxxxxx>, Joshua LeVasseur <jtl@xxxxxxxxxx>, Chris Wright <chrisw@xxxxxxxx>, Rik Van Riel <riel@xxxxxxxxxx>, Jyothy Reddy <jreddy@xxxxxxxxxx>, Jack Lo <jlo@xxxxxxxxxx>, Kip Macy <kmacy@xxxxxxxxxxx>, Jan Beulich <jbeulich@xxxxxxxxxx>, Ky Srinivasan <ksrinivasan@xxxxxxxxxx>, Wim Coekaerts <wim.coekaerts@xxxxxxxxxx>, Leendert van Doorn <leendert@xxxxxxxxxxxxxx>
Subject: [Xen-devel] Re: [RFC, PATCH 2/24] i386 Vmi config
From: Zachary Amsden <zach@xxxxxxxxxx>
Date: Tue, 14 Mar 2006 07:55:03 -0800
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Christoph Hellwig wrote:
On Mon, Mar 13, 2006 at 10:00:27AM -0800, Zachary Amsden wrote:
Introduce the basic VMI sub-arch configuration dependencies.  VMI kernels only
are designed to run on modern hardware platforms.  As such, they require a
working APIC, and do not support some legacy functionality, including APM BIOS,
ISA and MCA bus systems, PCI BIOS interfaces, or PnP BIOS (by implication of
dropping ISA support).  They also require a P6 series CPU.

That's pretty bad because distributors need another kernel still.  At least
a working APIC isn't quite as common today as it should.

It doesn't need to be a fully functional APIC. It just needs to not have one particular bug - Pentium processor erratum 11AP. There is no reason that most of these requirements can't be dropped. We used to have a lot more functionality and legacy support turned off, and we gradually turned it back on. Turning on the BIOS interfaces will cause complications for a VMI kernel running in a hypervisor - since it can't invoke non-virtualized BIOS code. So it does require a bit of conditional logic, which is pretty easy, but we haven't got around to doing yet.

Zach

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