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From: "Jan Beulich" <JBeulich@suse.com>
To: Quan Xu <quan.xu@intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>, Feng Wu <feng.wu@intel.com>,
	George Dunlap <George.Dunlap@eu.citrix.com>,
	Liu Jinsong <jinsong.liu@alibaba-inc.com>,
	Dario Faggioli <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: Thu, 24 Mar 2016 08:37:27 -0600	[thread overview]
Message-ID: <56F409B702000078000E02D0@prv-mh.provo.novell.com> (raw)
In-Reply-To: <945CA011AD5F084CBEA3E851C0AB28894B86B54F@SHSMSX101.ccr.corp.intel.com>

>>> On 24.03.16 at 15:12, <quan.xu@intel.com> wrote:
> On March 24, 2016 5:59pm, <JBeulich@suse.com> wrote:
>> >>> On 24.03.16 at 10:02, <quan.xu@intel.com> wrote:
>> > On March 18, 2016 5:49pm, <JBeulich@suse.com> wrote:
> 
> 
>> >    3. For iommu_{,un}map_page(), we'd better fix it as a normal error,
>> > as the error is not only from iommu flush, .e.g, '-ENOMEM'.
>> >      So, we need to {,un}map from the IOMMU, return an error, and roll
>> > back the failed operation( .e.g, unmap EPT).
>> 
>> Well, if that possible in a provably correct way, then sure. But be clear - when
>> the failure occurs while unmapping, unmapping the EPT entry obviously can't be
>> the solution, 
> 
> I hope we discuss about the same point as bellow?:
>    ept_set_entry()
>    {
>     ....
>           if ( iommu_flags )
>                 for ( i = 0; i < (1 << order); i++ )
>                     iommu_map_page(d, gfn + i, mfn_x(mfn) + i, iommu_flags);
>             else
>                 for ( i = 0; i < (1 << order); i++ )
>                     iommu_unmap_page(d, gfn + i);
>     ....
>    }
> 
> 
>> you'd need a true roll back.
> 
> Does it refer to as:
> If the old entry is present, we need to write back the old entry? 

Yes, but that's not as simple as it sounds: You also need to take
care of the splitting of super pages which may have occurred.

Jan


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  reply	other threads:[~2016-03-24 14:37 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
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 [this message]
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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