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Re: [Xen-devel][VTD] 1:1 mapping for dom0 exhausts xenheap on x86/32 wit

To: "Han, Weidong" <weidong.han@xxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel][VTD] 1:1 mapping for dom0 exhausts xenheap on x86/32 with 4G memory
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 28 Sep 2007 08:59:40 +0100
Cc: "Kay, Allen M" <allen.m.kay@xxxxxxxxx>
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Thread-topic: [Xen-devel][VTD] 1:1 mapping for dom0 exhausts xenheap on x86/32 with 4G memory
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On 28/9/07 08:51, "Han, Weidong" <weidong.han@xxxxxxxxx> wrote:

>>> I already had a try to use alloc_domheap_page() instead of
>>> alloc_xenheap_page(). It works on x86/64. But it doesn't work on
>>> x86/32. 
>> Use map_domain_page(), or live with only x86/64 support. You can't
>> burn x86/32's limited xenheap space on iommu page tables.
>>  -- Keir
> The 1:1 mapping page table is setup for both dom0 and PV domains. Is it
> no problem to use alloc_domheap_page() and map_domain_page()?

It's fine. Pass NULL as the domain pointer to alloc_domheap_page() and you
get anonymous pages from the global domain heap. The 'domain' in the name of
alloc_domheap_page() and map_domain_page() functions is a bit misleading!

 -- Keir

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