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Re: [Xen-devel] [PATCH v2 2/2] xen/x86: hap: Clean-up and harden hap_enable()

On 04/02/2020 13:16, Durrant, Paul wrote:
-----Original Message-----
From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of
Julien Grall
Sent: 04 February 2020 13:06
To: xen-devel@xxxxxxxxxxxxxxxxxxxx
Cc: julien@xxxxxxx; Wei Liu <wl@xxxxxxx>; George Dunlap
<george.dunlap@xxxxxxxxxxxxx>; Andrew Cooper <andrew.cooper3@xxxxxxxxxx>;
Grall, Julien <jgrall@xxxxxxxxxx>; Jan Beulich <jbeulich@xxxxxxxx>; Roger
Pau Monné <roger.pau@xxxxxxxxxx>
Subject: [Xen-devel] [PATCH v2 2/2] xen/x86: hap: Clean-up and harden

From: Julien Grall <jgrall@xxxxxxxxxx>

Unlike shadow_enable(), hap_enable() can only be called once during
domain creation and with the mode equal to mode equal to
PG_external | PG_translate | PG_refcounts.

If it were called twice, then we might have something interesting
problem as the p2m tables would be re-allocated (and therefore all the
mappings would be lost).

There are two tests in p2m_alloc_tabl2: whether the domain has memory 
allocated, and whether the domain already has a p2m. Can these now be dropped?

I don't think so. They are still necessary for the shadow page-tables. AFAICT, they are enabled via a DOMCTL.


Julien Grall

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