[Xen-devel] Re: [RFC] fix xen_in_range()

["Jan Beulich" <jbeulich@xxxxxxxxxx>]

>>> Keir Fraser <keir.fraser@xxxxxxxxxxxxx> 23.04.09 09:25 >>>
>On 23/04/2009 00:53, "Cihula, Joseph" <joseph.cihula@xxxxxxxxx> wrote:
>
>> Unfortunately, the frametable is only contiguous in the virtual address 
>> space,
>> so one can't simply take __pa() of its start and end.  And since it is quite
>> large, iterating through each page to gets its phys addr adds a perceptible
>> delay when that check has to be done for each page of physical memory (as is
>> the case in the only caller, the VT-d routine that maps memory for dom0).  
>> But
>> it also appears that we can't convert the phys addr arguments into their virt
>> addrs to compare with the contiguous frametable range because they will
>> convert to the DIRECTMAP va's instead.
>
>The frametable is allocated in aligned 2MB chunks. So you can check at that
>granularity rather than 4kB.

... and perhaps allocation should be attempted in 1Gb chunks when the table
size is getting close to or exceeding 1Gb (and 1Gb-pages are supported). Or,
since the space mapped is larger than the space allocated anyway, the
condition might be just that of 1Gb-pages being supported (provided a 1Gb-
aligned chunk can be allocated).

Jan


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