Re: [Xen-devel] [PATCH][XEN] construct_dom0: Initialize variable before use

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 29/11/07 13:02, "Christoph Egger" <Christoph.Egger@xxxxxxx> wrote:

> Without this fix, d->arch.physaddr_bitsize is 0 in
> domain_clamp_alloc_bitsize(). This causes all attempts to
> XENMEM_increase_reservation with bits > 0 to fail. More precisely,
> __alloc_domheap_pages() returns NULL.
> This impacts Xen heap allocation in general.
> Question: How did that work on Linux Dom0?

Yes, that's pretty broken. It works for Linux because Linux allocates its
lowmem I/o pages (e.g., swiotlb) using the XENMEM_exchange command, and that
allocates the new memory anonymously in the first instance. This defeats the
bitsize clamp check (which is okay just now because our truncation of the
phsyical memory map to 166GB is sufficient to ensure that compat domUs can
address all memory).

 -- Keir



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