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

[Julien Grall <julien@xxxxxxx>]

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
> > hap_enable()
> >
> > 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.
Cheers,

--
Julien Grall

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