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

On Thursday 29 November 2007 14:37:24 Christoph Egger wrote:
> 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.

Keir: Can you also put this fix onto your patch-queue for Xen 3.1.3, please?


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