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Re: [Xen-devel] Re: [PATCH 0/6] xen: don't call vmalloc_sync_all() when

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: Re: [Xen-devel] Re: [PATCH 0/6] xen: don't call vmalloc_sync_all() when mapping foreign pages
From: David Vrabel <david.vrabel@xxxxxxxxxx>
Date: Fri, 23 Sep 2011 12:18:48 +0100
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, "linux-kernel@xxxxxxxxxxxxxxx" <linux-kernel@xxxxxxxxxxxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, Stefano Stabellini <Stefano.Stabellini@xxxxxxxxxxxxx>
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On 22/09/11 22:19, Jeremy Fitzhardinge wrote:
> 
> But I'd be happier pretending that vmalloc_sync_* just doesn't exist,
> and deal with it at the hypercall level - in the short term, by just
> making sure that the callers touch all those pages before passing them
> into the hypercall.

I don't think you can access the pages at the addresses allocated with
alloc_vm_area() because the pages don't exist yet and there's a check of
pte_present() in vmalloc_fault() and I think an Oops will be reported.

David

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