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Re: [Xen-devel] [PATCH 5/8] xen/vmap: allow vmap() to be called during early boot

Hi David,

On 01/02/2020 00:33, David Woodhouse wrote:
From: David Woodhouse <dwmw@xxxxxxxxxxxx>

I am a bit concerned with this change, particularly the consequence this have for the page-tables. There is an assumption that intermediate page-tables allocated via the boot allocator will never be freed.

On x86, a call to vunmap() will not free page-tables, but a subsequent call to vmap() may free it depending on the mapping size. So we would call free_domheap_pages() rather than init_heap_pages().

I am not entirely sure what is the full consequence, but I think this is a call for investigation and write it down a summary in the commit message.


Julien Grall

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