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From: George Dunlap <George.Dunlap@eu.citrix.com>
To: Malcolm Crossley <malcolm.crossley@citrix.com>
Cc: Keir Fraser <keir@xen.org>,
	Tamas K Lengyel <tamas.k.lengyel@gmail.com>,
	George Dunlap <george.dunlap@citrix.com>,
	Xen-devel <xen-devel@lists.xen.org>,
	Jan Beulich <jbeulich@suse.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	"Lengyel, Tamas" <tlengyel@novetta.com>
Subject: Re: [PATCH] xen: Restore p2m_access_t enum order to allow bitmask semantics
Date: Mon, 14 Mar 2016 18:12:18 +0000	[thread overview]
Message-ID: <CAFLBxZaOLYF6YzQN0Z2Mgp6h29SEyYLwXcnJd0iRC5ZAAkG+1Q@mail.gmail.com> (raw)
In-Reply-To: <56E28791.9040908@citrix.com>

On Fri, Mar 11, 2016 at 8:53 AM, Malcolm Crossley
<malcolm.crossley@citrix.com> wrote:
> On 10/03/16 20:48, Tamas K Lengyel wrote:
>> On Wed, Mar 9, 2016 at 5:30 PM, George Dunlap <george.dunlap@citrix.com
>> <mailto: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 <mailto: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.
> I can't see any other usages of p2m_access_t without enum values either.

Great, thanks:

Reviewed-by: George Dunlap <george.dunlap@citrix.com>

Xen-devel mailing list

      reply	other threads:[~2016-03-14 18:12 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
2016-03-11  8:53     ` Malcolm Crossley
2016-03-14 18:12       ` George Dunlap [this message]

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