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From: Tamas K Lengyel <tamas.k.lengyel@gmail.com>
To: George Dunlap <george.dunlap@citrix.com>
Cc: Keir Fraser <keir@xen.org>,
	George Dunlap <george.dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Xen-devel <xen-devel@lists.xen.org>,
	Jan Beulich <jbeulich@suse.com>,
	"Lengyel, Tamas" <tlengyel@novetta.com>,
	Malcolm Crossley <malcolm.crossley@citrix.com>
Subject: Re: [PATCH] xen: Restore p2m_access_t enum order to allow bitmask semantics
Date: Thu, 10 Mar 2016 21:48:04 +0100	[thread overview]
Message-ID: <CABfawh=LbubJO-Od9b06YLG=8Up8MJFdObU1cK9CCui-ObqPSw@mail.gmail.com> (raw)
In-Reply-To: <56E04FBA.2030404@citrix.com>


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On Wed, Mar 9, 2016 at 5:30 PM, George Dunlap <george.dunlap@citrix.com>
wrote:

> On 08/03/16 15:30, Malcolm Crossley wrote:
> > Nested hap code assumed implict bitmask semantics of the p2m_access_t
> > enum prior to C/S 4c63692d7c38c5ac414fe97f8ef37b66e05abe5c
> >
> > The change to the enum ordering broke this assumption and caused
> functional
> > problems for the nested hap code. As it may be error prone to audit and
> find
> > all other p2m_access users assuming bitmask semantics, instead restore
> the
> > previous enum order and make it explict that bitmask semantics are to be
> > preserved for the read, write and execute access types.
> >
> > Signed-off-by: Malcolm Crossley <malcolm.crossley@citrix.com>
>
> Looks good; but following up Jan's point, could you do a brief survey of
> the places where the p2m_access values are used, and confirm that none
> of them now implicitly assume that p2m_access_rwx is zero?
>
> (Or Tamas, can you say that you're reasonably certain nothing has now
> come to depend on the value of p2m_access_rwx being zero?)
>

Yes, from my perspective it's all fine as checks of p2m_access values are
done with the enum names and not the values directly.

Tamas

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  reply	other threads:[~2016-03-10 20:48 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-08 15:30 [PATCH] xen: Restore p2m_access_t enum order to allow bitmask semantics Malcolm Crossley
2016-03-08 15:36 ` Andrew Cooper
2016-03-08 15:52 ` Jan Beulich
2016-03-08 15:58   ` Tamas K Lengyel
2016-03-09 16:30 ` George Dunlap
2016-03-10 20:48   ` Tamas K Lengyel [this message]
2016-03-11  8:53     ` Malcolm Crossley
2016-03-14 18:12       ` George Dunlap

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