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[Xen-devel] Re: is_xen_swiotlb_buffer() vs CONFIG_HIGHMEM

To: "Jeremy Fitzhardinge" <jeremy@xxxxxxxx>
Subject: [Xen-devel] Re: is_xen_swiotlb_buffer() vs CONFIG_HIGHMEM
From: "Jan Beulich" <JBeulich@xxxxxxxxxx>
Date: Wed, 16 Dec 2009 07:40:48 +0000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
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>>> Jeremy Fitzhardinge <jeremy@xxxxxxxx> 15.12.09 19:34 >>>
>On 12/14/2009 07:02 AM, Jan Beulich wrote:
>> shouldn't is_xen_swiotlb_buffer() also check against e.g. highstart_pfn
>> to deal with wrap-around potentially leading to aliasing of
>> [xen_io_tlb_start,xen_io_tlb_end)?
>>    
>
>So what you're saying is that if the pfn is for a high page, then 
>"__va(pfn << PAGE_SHIFT);" is simply invalid.  The resulting addr is 
>undefined, and may end up erroneously aliasing with the xen tlb buffer.
>
>Do I understand your concern properly?

Yes.

Jan


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