Re: [Xen-devel] Linux'es free_initmem() on Xen

[David Vrabel <david.vrabel@xxxxxxxxxx>]

On 02/02/16 14:10, Jan Beulich wrote:
>>>> On 02.02.16 at 14:30, <david.vrabel@xxxxxxxxxx> wrote:
>> On 02/02/16 12:44, Jan Beulich wrote:
>>> All,
>>>
>>> while looking into some of the DEBUG_WX issues I came across
>>> aforementioned function and started wondering how pv-ops gets
>>> away without the unmapping XenoLinux has always been doing
>>> (in free_init_pages()).
>>
>> Um.  I'm not sure why you think something needs to be unmapped.  This is
>> freeing the pages back to the page allocator -- thus the pages still
>> need to be mapped.
> 
> In the 1:1 mapping, yes. But the secondary mapping in the kernel
> VA range is not needed anymore, and (unless accounted for) would
> get in the way of said operations.

The PMDs are shared between the two mappings. See
xen_setup_kernel_pagetable().

David

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