RE: [PATCH v3 4/5] intel_iommu: Fix address space unmap

[Duan, Zhenzhong]

>-----Original Message-----
>From: Peter Xu <peterx@redhat.com>
>Sent: Friday, June 9, 2023 9:37 PM
>To: Duan, Zhenzhong <zhenzhong.duan@intel.com>
>Cc: qemu-devel@nongnu.org; mst@redhat.com; jasowang@redhat.com;
>pbonzini@redhat.com; richard.henderson@linaro.org; eduardo@habkost.net;
>marcel.apfelbaum@gmail.com; alex.williamson@redhat.com;
>clg@redhat.com; david@redhat.com; philmd@linaro.org;
>kwankhede@nvidia.com; cjia@nvidia.com; Liu, Yi L <yi.l.liu@intel.com>; Peng,
>Chao P <chao.p.peng@intel.com>
>Subject: Re: [PATCH v3 4/5] intel_iommu: Fix address space unmap
>
>On Fri, Jun 09, 2023 at 03:31:46AM +0000, Duan, Zhenzhong wrote:
>>
>>
>> >-----Original Message-----
>> >From: Peter Xu <peterx@redhat.com>
>> >Sent: Thursday, June 8, 2023 9:48 PM
>> >To: Duan, Zhenzhong <zhenzhong.duan@intel.com>
>> >Cc: qemu-devel@nongnu.org; mst@redhat.com; jasowang@redhat.com;
>> >pbonzini@redhat.com; richard.henderson@linaro.org;
>> >eduardo@habkost.net; marcel.apfelbaum@gmail.com;
>> >alex.williamson@redhat.com; clg@redhat.com; david@redhat.com;
>> >philmd@linaro.org; kwankhede@nvidia.com; cjia@nvidia.com; Liu, Yi L
>> ><yi.l.liu@intel.com>; Peng, Chao P <chao.p.peng@intel.com>
>> >Subject: Re: [PATCH v3 4/5] intel_iommu: Fix address space unmap
>> >
>> >On Thu, Jun 08, 2023 at 05:52:30PM +0800, Zhenzhong Duan wrote:
>> >> During address space unmap, corresponding IOVA tree entries are
>> >> also removed. But DMAMap is set beyond notifier's scope by 1, so in
>> >> theory there is possibility to remove a continuous entry above the
>> >> notifier's scope but falling in adjacent notifier's scope.
>> >
>> >This function is only called in "loop over all notifiers" case (or
>> >replay() that just got removed, but even so there'll be only 1
>> >notifier normally iiuc at least for vt-d), hopefully it means no bug
>> >exist (no Fixes needed, no backport needed either), but still worth fixing 
>> >it
>up.
>>
>> Not two notifiers as vtd-ir splits for vt-d?
>
>The two notifiers will all be attached to the same IOMMU mr, so
>IOMMU_NOTIFIER_FOREACH() will loop over them all always?
Yes.
>
>And this actually shouldn't matter, IMHO, as the IR split has the 0xfeeXXXXX
>hole only, so when notifying with end=0xfee00000 (comparing to
>end=0xfedfffff) it shouldn't make a difference iiuc because there should have
>no iova entry at 0xfee00000 anyway in the tree.
Clear.

Thanks
Zhenzhong