This is an archived copy of the Xen.org mailing list, which we have preserved to ensure that existing links to archives are not broken. The live archive, which contains the latest emails, can be found at http://lists.xen.org/
Home Products Support Community News


Re: [Xen-devel] APIC initialization when config file has "apic=0".

To: "Petersson, Mats" <Mats.Petersson@xxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] APIC initialization when config file has "apic=0".
From: Keir Fraser <keir@xxxxxxxxxxxxx>
Date: Thu, 29 Mar 2007 18:52:21 +0100
Delivery-date: Thu, 29 Mar 2007 18:55:13 +0100
Envelope-to: Keir.Fraser@xxxxxxxxxxxx
In-reply-to: <907625E08839C4409CE5768403633E0B018E1B52@xxxxxxxxxxxxxxxxx>
List-help: <mailto:xen-devel-request@lists.xensource.com?subject=help>
List-id: Xen developer discussion <xen-devel.lists.xensource.com>
List-post: <mailto:xen-devel@lists.xensource.com>
List-subscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=subscribe>
List-unsubscribe: <http://lists.xensource.com/cgi-bin/mailman/listinfo/xen-devel>, <mailto:xen-devel-request@lists.xensource.com?subject=unsubscribe>
Sender: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
Thread-index: AcdyJYQIV4X9azsRTli55zwoSm/8hQABXvQd
Thread-topic: [Xen-devel] APIC initialization when config file has "apic=0".
User-agent: Microsoft-Entourage/
On 29/3/07 18:13, "Petersson, Mats" <Mats.Petersson@xxxxxxx> wrote:

> To me, if config file has "apic=0", the APIC should not stop the guest
> from being able to use the 8259 as an interrupt source. But this appears
> to be the case - and as far as I can see, it's because the APIC mode is
> not initialized (correctly/at all) when the guest is started.
> Shouldn't "apic=0" mean that the guest appears like there's no APIC? In
> which case, this should mean that the IA32_APIC_BASE MSR should have the
> APIC disable bit set.

apic=0 simply means we don't advertise the APIC in the BIOS tables. It's
always physically present, and enabled by default. Its configuration is
identical to what you would get from a real physical processor at power on.

Bear in mind that platform features such as 'virtual wire' mode are usually
set up by the BIOS, which you are entirely circumventing by replacing
hvmloader. You can get around this particular problem by copying hvmloader's
apic_setup() function. If you want PCI functionality you may also want

 -- Keir

Xen-devel mailing list

<Prev in Thread] Current Thread [Next in Thread>