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From: "Jan Beulich" <JBeulich@suse.com>
To: Malcolm Crossley <malcolm.crossley@citrix.com>, tamas@tklengyel.com
Cc: george.dunlap@eu.citrix.com, andrew.cooper3@citrix.com,
	keir@xen.org, xen-devel@lists.xen.org
Subject: Re: [PATCH] xen: Restore p2m_access_t enum order to allow bitmask semantics
Date: Tue, 08 Mar 2016 08:52:17 -0700	[thread overview]
Message-ID: <56DF034102000078000DA7DB@prv-mh.provo.novell.com> (raw)
In-Reply-To: <1457451028-3808-1-git-send-email-malcolm.crossley@citrix.com>

>>> 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?


Xen-devel mailing list

  parent reply	other threads:[~2016-03-08 15:52 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 [this message]
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

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