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Re: [Xen-devel] Can I specify a physical memory region for a domU

To: Eric Camachat <eric.camachat@xxxxxxxxx>
Subject: Re: [Xen-devel] Can I specify a physical memory region for a domU
From: Tim Deegan <tim@xxxxxxx>
Date: Thu, 8 Sep 2011 09:50:02 +0100
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At 17:47 -0700 on 07 Sep (1315417666), Eric Camachat wrote:
> Hi,
> 
> I am porting our drivers to XEN's PV domU (with PV PCI passthrouth), I
> have to allocate a memory block and tell the hardware to access it.
> But the hardware can address 32-bit only, so I want dedicate a region
> of memory that below 2GB for the domU only.
> How do that in XEN?

Use the XENMEM_echange memory_op hypercall.  You can specify a bit-width
for the pages you want returned. 

Of course, on a full Xen host there may be no 32-bit-clean memory left.
Xen tries to allocate the higher addresses first to avoid that, but
there's no guarantee.

Tim.

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