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Re: [Xen-devel] xen_create_contiguous_region - Regarding

To: Jambunathan K <jambunathan@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: Re: [Xen-devel] xen_create_contiguous_region - Regarding
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Fri, 06 Apr 2007 12:07:05 +0100
Cc: sanjeev@xxxxxxxxxx
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On 6/4/07 11:46, "Jambunathan K" <jambunathan@xxxxxxxxxx> wrote:

> Given that we prefer to maintain our own bounce buffers, I could neither
> find a dependable API that let the driver allocate machine contiguous
> memory (that could later be *pci_map_singled*) nor find a suitable hook
> to xen_create_contiguous_region.

pci_map_single() will do what you want automatically. If you really want to
allocate contiguous memory yourself, allocate it then call
xen_create_contiguous_region().

> As an aside, is there a tweak to "increase" contiguous memory regions
> available so that xen_create_contiguous_regions() succeeds. On DomUs,
> when swiotlb is enabled, I see some crashes which I would like to avoid
> by redistributing memory resources.

Xen will try to maintain contiguity as far as possible, but it cannot
defragment the memory map.

 -- Keir



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