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From: "Xu, Quan" <quan.xu@intel.com>
To: George Dunlap <George.Dunlap@eu.citrix.com>
Cc: "Tian, Kevin" <kevin.tian@intel.com>, Keir Fraser <keir@xen.org>,
	"Nakajima, Jun" <jun.nakajima@intel.com>,
	Liu Jinsong <jinsong.liu@alibaba-inc.com>,
	Dario Faggioli <dario.faggioli@citrix.com>,
	"xen-devel@lists.xen.org" <xen-devel@lists.xen.org>,
	Jan Beulich <jbeulich@suse.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	"Wu, Feng" <feng.wu@intel.com>
Subject: Re: [PATCH 1/2] IOMMU/MMU: Adjust top level functions for VT-d Device-TLB flush error.
Date: Fri, 18 Mar 2016 03:19:05 +0000	[thread overview]
Message-ID: <945CA011AD5F084CBEA3E851C0AB28894B867105@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <CAFLBxZZ9=vbcKQJS=NvjdNf+1uvOzSDOkAg8FNLDv3CC2ygXfw@mail.gmail.com>

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:
> >> diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c index
> >> c997b53..526548e 100644
> >> --- a/xen/arch/x86/mm.c
> >> +++ b/xen/arch/x86/mm.c
> >> @@ -2467,7 +2467,7 @@ static int __get_page_type(struct page_info
> *page, unsigned long type,
> >>                             int preemptible)  {
> >>      unsigned long nx, x, y = page->u.inuse.type_info;
> >> -    int rc = 0;
> >> +    int rc = 0, ret = 0;
> >>
> >>      ASSERT(!(type & ~(PGT_type_mask | PGT_pae_xen_l2)));
> >>
> >> @@ -2578,11 +2578,11 @@ static int __get_page_type(struct page_info
> *page, unsigned long type,
> >>          if ( d && is_pv_domain(d) && unlikely(need_iommu(d)) )
> >>          {
> >>              if ( (x & PGT_type_mask) == PGT_writable_page )
> >> -                iommu_unmap_page(d, mfn_to_gmfn(d,
> page_to_mfn(page)));
> >> +                ret = iommu_unmap_page(d, mfn_to_gmfn(d,
> page_to_mfn(page)));
> >>              else if ( type == PGT_writable_page )
> >> -                iommu_map_page(d, mfn_to_gmfn(d,
> page_to_mfn(page)),
> >> -                               page_to_mfn(page),
> >> -
> IOMMUF_readable|IOMMUF_writable);
> >> +                ret = iommu_map_page(d, mfn_to_gmfn(d,
> page_to_mfn(page)),
> >> +                                     page_to_mfn(page),
> >> +
> IOMMUF_readable|IOMMUF_writable);
> >>          }
> >>      }
> >>
> >> @@ -2599,6 +2599,9 @@ static int __get_page_type(struct page_info
> *page, unsigned long type,
> >>      if ( (x & PGT_partial) && !(nx & PGT_partial) )
> >>          put_page(page);
> >>
> >> +    if ( !rc )
> >> +        rc = ret;
> >> +
> >
> > What's this about?  If the iommu_[un]map_page() operation times out,
> > we still go through with calling alloc_page_type(); and if
> > alloc_page_type() fails we return its failure value, but if it
> > succeeds, we return the error from iommu_[un]map_page()?
> >
> >>      return rc;
> >>  }
> >>
> >> diff --git a/xen/arch/x86/mm/p2m-ept.c b/xen/arch/x86/mm/p2m-ept.c
> >> index 3cb6868..f9bcce7 100644
> >> --- 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 */


Right?

Quan

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  reply	other threads:[~2016-03-18  3:19 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-03-17  6:54 [PATCH 0/2] Check " 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 [this message]
2016-03-18  8:09         ` Jan Beulich
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

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