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[Xen-devel] Re: paging_domctl() missing break statements?

To: Paolo Bonzini <pbonzini@xxxxxxxxxx>, Tim Deegan <Tim.Deegan@xxxxxxxxxxxxx>
Subject: [Xen-devel] Re: paging_domctl() missing break statements?
From: Keir Fraser <keir.fraser@xxxxxxxxxxxxx>
Date: Wed, 23 Jun 2010 13:51:30 +0100
Cc: "xen-devel@xxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxx>, Jan Beulich <JBeulich@xxxxxxxxxx>
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On 23/06/2010 13:27, "Paolo Bonzini" <pbonzini@xxxxxxxxxx> wrote:

>>> The main switch statement in that function looks suspicious, and with no
>>> explicit comment saying that fall-through is intended it would seem like
>>> one or two break statements are actually missing. Comments?
>> 
>> Yep, looks like that was just working by blind luck.
>> 
>> Tim.

> This was never applied.

It was applied as 20954:b4041e7bbe1b but then reverted as
20987:c4301c2c727d:
"""
Revert 20954:b4041e7bbe1b "paging_domctl: Add missing breaks in switch stmt"

This fixed a fairly innocuous bug (OP_ENABLE/OP_OFF both don't work
properly) but unmasked a much nastier one (turning off shadow mode on
a PV guest crashes the hypervisor).

So, for now, we pick the less of two evils. We don't really much rely
on OP_ENABLE/OP_OFF anyway, as it happens.

Signed-off-by: Keir Fraser <keir.fraser@xxxxxxxxxx>
"""

 -- Keir



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