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Re: [Xen-devel] Setting page type for GDT page

To: Trammell Hudson <hudson@xxxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] Setting page type for GDT page
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 31 Aug 2007 17:21:25 +0100
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User-agent: Microsoft-Entourage/
The type code disagrees with you. There's still a writable mapping lurking
somewhere. Perhaps not in the page tables you are running on, though. What
do you do with the page tables that the domain builder provides you?

 -- Keir

On 31/8/07 17:15, "Trammell Hudson" <hudson@xxxxxxxxxxxxxx> wrote:

> I'm trying to install my own GDT in a lightweight kernel domU
> and am receiving an error from HYPERVISOR_set_gdt() that my page
> does not have the expected type.  I've made sure that the page is
> mapped read-only and walked the active page tables to check for
> any writable mappings.  There are two mappings of page 0x2abcd,
> both with only the present and user bits set:
> load_gdt_xen:313: Setting GDT page 0000006000524000 read-only
> Mappings of 0000006000524000 (page 000000002abcd000):
> PML1 0x6000024000[124] = 001000002abcd005 (va=0000000000524000 000 000 002
> 124)
> PML1 0x6000024000[124] = 001000002abcd005 (va=0000006000524000 000 180 002
> 124)
> load_gdt_xen:318: Setting GDT 0x6000524000 => 000000000002abcd (12 entries)
> (XEN) mm.c:1664:d10 Bad type (saw 00000000e8000001 != exp 00000000a0000000)
> for mfn 2abcd (pfn 524)
> load_gdt_xen:322: Unable to set GDT!  rc=-22

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