Messages in this thread | | | Date | Wed, 14 Dec 2011 17:17:08 +0100 | From | Joerg Roedel <> | Subject | Re: [PATCH 20/22] iommu/amd: Implement IO page-fault handler |
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On Wed, Dec 14, 2011 at 11:13:00AM -0500, Jerome Glisse wrote: > On Mon, Dec 05, 2011 at 02:34:35PM +0100, Joerg Roedel wrote: > > + npages = get_user_pages(fault->state->task, fault->state->mm, > > + fault->address, 1, write, 0, &page, NULL); > > + > > + if (npages == 1) > > + put_page(page); > > + else > > + set_pri_tag_status(fault->state, fault->tag, PPR_INVALID); > > I might be missing something on how mm work in linux but can't the page > in a vma change anytime (like being migrated to a node or being evicted > ...) I guess my question is when a fault happen is it because the task > page table have an invalid entry ?
Yes, but this is not a problem. When the page-fault handler signals completion of the page-fault back to the device it will start to re-walk the page-table. If the page-walker detects that the page is not there it will just signal the fault again. MMU-Notifiers take care of the TLB management.
> I was under the impression that their was a page table associated with > each iommu client. Thus that the task page table was never directly use. > But i haven't carrefully read all the patches.
The IOMMUv2 can handle x86 long-mode page-tables (including accessed/dirty bits). So it is easy to just re-use the task page-tables in the IOMMUv2.
Regards,
Joerg
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