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From: Tamas K Lengyel <tamas@tklengyel.com>
To: Jan Beulich <JBeulich@suse.com>
Cc: George Dunlap <george.dunlap@eu.citrix.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Malcolm Crossley <malcolm.crossley@citrix.com>,
	Keir Fraser <keir@xen.org>, Xen-devel <xen-devel@lists.xen.org>
Subject: Re: [PATCH] xen: Restore p2m_access_t enum order to allow bitmask semantics
Date: Tue, 8 Mar 2016 16:58:41 +0100	[thread overview]
Message-ID: <CABfawhnRqSLxkS3XE_BPnT8CwG4H=t6Fs8CP0Mb90e-ims+VnA@mail.gmail.com> (raw)
In-Reply-To: <56DF034102000078000DA7DB@prv-mh.provo.novell.com>


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On Tue, Mar 8, 2016 at 4:52 PM, Jan Beulich <JBeulich@suse.com> wrote:

> >>> On 08.03.16 at 16:30, <malcolm.crossley@citrix.com> 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.
>
> Makes sense, but how certain are you that ...
>
> > --- a/xen/include/xen/p2m-common.h
> > +++ b/xen/include/xen/p2m-common.h
> > @@ -15,14 +15,15 @@
> >   * default.
> >   */
> >  typedef enum {
> > -    p2m_access_rwx   = 0, /* The default access type when not used. */
>
> ... namely this has not meanwhile seen any implicit use somewhere?
>
> Tamas, the original commit talked about this as an optimization only.
> Can you confirm that there indeed was no other intention than the
> one claimed in that commit's description?
>

That's the only reason I recall as well, so from my perspective it's fine
to be reverted.

Tamas

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  reply	other threads:[~2016-03-08 15:58 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 [this message]
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

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