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Re: [Xen-devel] [PATCH] x86: adjust reserved bit page fault handling

To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] [PATCH] x86: adjust reserved bit page fault handling
From: "Jan Beulich" <jbeulich@xxxxxxxxxx>
Date: Fri, 01 Feb 2008 11:24:41 +0000
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Tim Deegan <Tim.Deegan@xxxxxxxxxx>
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>>> Keir Fraser <Keir.Fraser@xxxxxxxxxxxx> 01.02.08 11:54 >>>
>On 1/2/08 10:38, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:
>>> The shadow pagetable code deliberately introduces invalid pagetable
>>> entries as part of its fast-path treatment of MMIO and not-present
>>> entries in the guest tables, so paging_fault needs to be called for
>>> PFEC_reserved_bit faults.
>> Here's a replacement patch then, it would still be questionable whether
>> reserved bit faults should ever be propagated to a guest...
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxxxx>
>What problem does this patch solve?

When debugging the xen_change_pte_range() problem I mistakenly
interpreted a page fault error code 15 as being decimal (it really was
hex) and looked at the reserved bit fault handling. The patch is the
outcome of this; despite it turned out to not be a fault of this kind I
thought that tightening the handling (and adding the printing, since
reserved bit faults are [except in the case mentioned by Tim] always
bad) wouldn't be a bad idea.


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