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

["Christoph Egger" <Christoph.Egger@xxxxxxx>]

On Thursday 29 November 2007 14:28:00 Keir Fraser wrote:
> 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).

Thanks for clarification.
NetBSD Dom0 failed when allocating DMA-safe memory above 4GB.

Christoph


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