RE: [Xen-devel][VTD] 1:1 mapping for dom0 exhausts xenheap on x86/32 with 4G memory

["Han, Weidong" <weidong.han@xxxxxxxxx>]

Keir Fraser wrote:
> On 28/9/07 08:28, "Han, Weidong" <weidong.han@xxxxxxxxx> wrote:
> 
>> Keir Fraser wrote:
>>> alloc_domheap_page() instead of alloc_xenheap_page(), and use
>>> map_domain_page() to get temporary mappings when you need them. This
>>> costs nothing on x86/64, where all memory is permanently mapped.
>> 
>> 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()?

Weidong

> 
>>> Or it is *very* reasonable to only support vt-d on x86/64
>>> hypervisor. That's the configuration we care about by far the most,
>>> since 32-bit guests run fine on a 64-bit hypervisor, and of course
>>> all vt-d systems will be 64-bit capable.
>>> 
>>>  -- Keir
>>> 
>>> On 28/9/07 06:26, "Han, Weidong" <weidong.han@xxxxxxxxx> wrote:
>>> 
>>>> xenheap size is 9M on x86/32 xen, it's not enough to setup 1:1 page
>>>> tables for dom0. It causes dom0 cannot boot successfully. Setup 1:1
>>>> page table in domheap still might be a problem since the thinking
>>>> is to use the same 1:1 page table for both dom0 and PV domains.
>>>> Currently I think of two options: 1) go back to original method,
>>>> that's to say setup page table dynamically for dom0; 2) increase
>>>> xenheap size on x86/32. How do you think about? Thanks.
>>>> 
>>>> Weidong
>> 
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