From: "Jan Beulich" <JBeulich@suse.com>
To: George Dunlap <George.Dunlap@eu.citrix.com>, Quan Xu <quan.xu@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>, Feng Wu <feng.wu@intel.com>,
Liu Jinsong <jinsong.liu@alibaba-inc.com>,
DarioFaggioli <dario.faggioli@citrix.com>,
"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
Jun Nakajima <jun.nakajima@intel.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Keir Fraser <keir@xen.org>
Subject: Re: [PATCH 1/2] IOMMU/MMU: Adjust top level functions for VT-d Device-TLB flush error.
Date: Fri, 18 Mar 2016 02:09:53 -0600 [thread overview]
Message-ID: <56EBC5E102000078000DE376@prv-mh.provo.novell.com> (raw)
In-Reply-To: <945CA011AD5F084CBEA3E851C0AB28894B867105@SHSMSX101.ccr.corp.intel.com>
>>> On 18.03.16 at 04:19, <quan.xu@intel.com> wrote:
> On March 17, 2016 8:34pm, George Dunlap <George.Dunlap@eu.citrix.com> wrote:
>> On Thu, Mar 17, 2016 at 12:30 PM, George Dunlap
>> <George.Dunlap@eu.citrix.com> wrote:
>> > On Thu, Mar 17, 2016 at 6:54 AM, Quan Xu <quan.xu@intel.com> wrote:
>> >> --- a/xen/arch/x86/mm/p2m-ept.c
>> >> +++ b/xen/arch/x86/mm/p2m-ept.c
>> >> @@ -830,7 +830,15 @@ out:
>> >> {
>> >> if ( iommu_flags )
>> >> for ( i = 0; i < (1 << order); i++ )
>> >> - iommu_map_page(d, gfn + i, mfn_x(mfn) + i,
>> iommu_flags);
>> >> + {
>> >> + rc = iommu_map_page(d, gfn + i, mfn_x(mfn) + i,
>> iommu_flags);
>> >> + if ( rc )
>> >> + {
>> >> + while ( i-- > 0 )
>> >> + iommu_unmap_page(d, gfn + i);
>> >
>> > This won't unmap gfn+0 (since it will break out when i == 0 without
>> > calling unmap).
>>
>> Oh, no it won't, because the decrement is postfix.
>>
>> For us mere mortals, I'd appreciate a comment here like this:
>>
>> /* Postfix operator means we will call unmap with i == 0 */
>>
> Agreed.
> For these 2 points, to summarize:
> - adding "unlikely()" to the if() condition, e.g. if ( unlikely(rc) )
> - adding a comment:
> /* Postfix operator means we will call unmap with i == 0 */
To be honest, I'm opposed to the addition of such comments.
See also the parallel discussion rooted at
http://lists.xenproject.org/archives/html/xen-devel/2016-03/msg01779.html
Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel
next prev parent reply other threads:[~2016-03-18 8:09 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-17 6:54 [PATCH 0/2] Check VT-d Device-TLB flush error Quan Xu
2016-03-17 6:54 ` [PATCH 1/2] IOMMU/MMU: Adjust top level functions for " Quan Xu
2016-03-17 7:32 ` Tian, Kevin
2016-03-17 7:58 ` Jan Beulich
2016-03-17 8:00 ` Tian, Kevin
2016-03-17 12:30 ` George Dunlap
2016-03-17 12:33 ` George Dunlap
2016-03-18 3:19 ` Xu, Quan
2016-03-18 8:09 ` Jan Beulich [this message]
2016-03-24 6:45 ` Xu, Quan
2016-03-18 7:54 ` Xu, Quan
2016-03-18 8:19 ` Jan Beulich
2016-03-18 9:09 ` Xu, Quan
2016-03-18 9:29 ` Jan Beulich
2016-03-18 9:38 ` Dario Faggioli
2016-03-18 9:48 ` Jan Beulich
2016-03-21 6:18 ` Tian, Kevin
2016-03-21 12:22 ` Jan Beulich
2016-03-24 9:02 ` Xu, Quan
2016-03-24 9:58 ` Jan Beulich
2016-03-24 14:12 ` Xu, Quan
2016-03-24 14:37 ` Jan Beulich
2016-03-17 17:14 ` Jan Beulich
2016-03-28 3:33 ` Xu, Quan
2016-03-29 7:20 ` Jan Beulich
2016-03-30 2:28 ` Xu, Quan
2016-03-30 2:35 ` Xu, Quan
2016-03-30 8:05 ` Jan Beulich
2016-03-17 6:54 ` [PATCH 2/2] IOMMU/MMU: Adjust low " Quan Xu
2016-03-17 7:37 ` Tian, Kevin
2016-03-18 2:30 ` Xu, Quan
2016-03-18 8:06 ` Jan Beulich
2016-03-21 5:01 ` Tian, Kevin
2016-03-17 15:31 ` George Dunlap
2016-03-18 6:57 ` Xu, Quan
2016-03-18 10:20 ` Jan Beulich
2016-03-25 9:27 ` Xu, Quan
2016-03-29 7:36 ` Jan Beulich
2016-04-11 3:09 ` Xu, Quan
2016-04-11 3:27 ` Xu, Quan
2016-04-11 16:34 ` Jan Beulich
2016-04-12 1:09 ` Xu, Quan
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=56EBC5E102000078000DE376@prv-mh.provo.novell.com \
--to=jbeulich@suse.com \
--cc=George.Dunlap@eu.citrix.com \
--cc=andrew.cooper3@citrix.com \
--cc=dario.faggioli@citrix.com \
--cc=feng.wu@intel.com \
--cc=jinsong.liu@alibaba-inc.com \
--cc=jun.nakajima@intel.com \
--cc=keir@xen.org \
--cc=kevin.tian@intel.com \
--cc=quan.xu@intel.com \
--cc=xen-devel@lists.xen.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).