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[Xen-devel] Double mapping of iomem assertion

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: [Xen-devel] Double mapping of iomem assertion
From: Kieran Mansley <kmansley@xxxxxxxxxxxxxx>
Date: Wed, 17 Oct 2007 14:25:17 +0100
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We have two drivers that both map a region of IO memory from a PCI
device.  This works fine on Linux, but in xen dom0 we hit an assertion
in arch/i386/mm/ioremap-xen.c:direct_remap_area_pte_fn() when doing the
second ioremap():

        BUG_ON(!pte_none(*pte));

It's not clear to me whether this is just an over-eager assertion or if
this operation is genuinely not supported on Xen.  The assertion doesn't
seem to be related to the operation of that function, and if I remove it
everything seems to work fine.

Is anyone who is more familiar with this code able to throw any light on
the reason for the assertion?

Thanks

Kieran


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