Re: [Xen-devel] loading IDT in xen?

To:	"Jun Koi" <junkoi2004@xxxxxxxxx>
Subject:	Re: [Xen-devel] loading IDT in xen?
From:	"余上" <yusunn@xxxxxxxxx>
Date:	Thu, 31 Jan 2008 15:57:34 +0800
Cc:	xen-devel@xxxxxxxxxxxxxxxxxxx
Delivery-date:	Wed, 30 Jan 2008 23:57:58 -0800
Dkim-signature:	v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; bh=zarOniGlr/7/1yL2qlnFjdCBZSFgGhjwS5oGwe4tf3k=; b=BTP2jUzcnMdDq0lUkbLUqrP0fNtt7GZv3dHG+uV/7u+/QEfxF4dcbOzqQpT3Ro6jJdZbcq2B70+F6GYvfyqeEE7PDJrlJKFvElkV8Nvmj2JVIu2GSws11VTsmMJlu63C7++FW6Kz0YG1vSwspq9mf1IhgApykxd2Gsg2sNvCSKU=
Domainkey-signature:	a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=message-id:date:from:to:subject:cc:in-reply-to:mime-version:content-type:content-transfer-encoding:content-disposition:references; b=Ba6k705upB+OTu8NO+zlCs4nT8o0/NtYzFODZVFpCrPI3EQdsaedE14rCfxwd9P0JyUPMcCGrk1J/pYpsJVfipJL3ir6UrBO1lwC70dU0naokT5YF08V8RUCNDFmteguX03BGVUIz+/dKRLrJImHmhjhXBfU0YC97jWEmHL/RNU=
Envelope-to:	www-data@xxxxxxxxxxxxxxxxxx
In-reply-to:	<fdaac4d50801302329m85350a7q4c47336852a34eac@xxxxxxxxxxxxxx>
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>
References:	<fdaac4d50801301946y89d1f08i80ff8d592795eb20@xxxxxxxxxxxxxx> <298d852f0801302256k6f9a2e6at2b326aafec894524@xxxxxxxxxxxxxx> <fdaac4d50801302329m85350a7q4c47336852a34eac@xxxxxxxxxxxxxx>
Sender:	xen-devel-bounces@xxxxxxxxxxxxxxxxxxx

I think maybe it is just some kind of coding style ? Or necessary for
CPU state transition ?

2008/1/31, Jun Koi <junkoi2004@xxxxxxxxx>:
> On 1/31/08, 余上 <yusunn@xxxxxxxxx> wrote:
> > There is another IDTR reload in x86_32.S at line 15 , where the
> > protected mode IDT vectors are initialized with ignore_int handler
> > firstly. Then trap_init called from __xen_start will setup the formal
> > IDT vectors .
>
> Now I see that. But the the question is: why we have to setup a
> "dummy" IDT in trampoline.S like that???
>
> Thanks,
> Jun
>
>
> >
> > 2008/1/31, Jun Koi <junkoi2004@xxxxxxxxx>:
> > > I am looking at the hypervisor code to see how Xen setup the IDT. But
> > > it seems that the code in protected mode reuses the real mode IDT?
> > >
> > > In arch/x86/boot/trampoline.S we have at several places:
> > >
> > > lidt bootsym(idt_48)
> > >
> > > And idt_48 is defined as:
> > >
> > > idt_48: .word 0,0,0 # base = limit = 0
> > >
> > > And in nowhere we initialize idt_48, which means idt_48 reuses real
> > > mode IDT table. However, real mode IDT table has different format than
> > > protected mode IDT, so this doesnt look to work for me.
> > >
> > > Definitely I miss something here. Anybody could enlighten me how IDT
> > > setting in protected mode work?
> > >
> > > Thanks,
> > > Jun
> > >
>

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel

WARNING - OLD ARCHIVES

xen-devel

Re: [Xen-devel] loading IDT in xen?