Re: [Xen-devel] [PATCH] AMD IOMMU: Defer IO pagetable construction until device assignment

[Wei Wang2 <wei.wang2@xxxxxxx>]

On Wed, 2008-04-02 at 16:07 +0100, Keir Fraser wrote:
> Then the logic is wrong because new p2m entries could be created after
> construct_p2m_mapping() is completed but before reassign_device() makes the
> guest's pdev_list non-empty.
Yes, thanks for catching that.
> I think you should leave p2m.c as it is, and then synchronise on creation of
> the iommu tables from within amd_iommu_map_page(). You already have a
> mapping_lock in there which might do the trick.
I will update it. Maybe I need a new flag to indicate that I/O page tables has 
been synchronised..

Wei

>  -- Keir
> 
> On 2/4/08 15:56, "Wei Wang2" <wei.wang2@xxxxxxx> wrote:
> 
> > I just want to make sure that no new p2m entries are written during the
> > copy procedure.
> > Wei 
> > On Wed, 2008-04-02 at 16:52 +0200, Keir Fraser wrote:
> >> On 2/4/08 15:13, "Wei Wang2" <wei.wang2@xxxxxxx> wrote:
> >> 
> >>> During HVM domain creation, I/O page tables are filled by coping p2m
> >>> entries from p2m table, which is a useless step for non-passthru
> >> domain.
> >>> This patch defers I/O page table construction until the moment of
> >> device
> >>> assignment. In case that pci devices are never assigned or hot
> >> plugged,
> >>> the unnecessary duplication will be avoid.
> >> 
> >> You can't duplicate p2m_lock() and p2m_unlock(). Why do you need to
> >> protect
> >> your new function with that lock anyway?
> >> 
> >>  -- Keir
> >> 
> >> 
> >> 
> >> 
> >> 
> > 
> > 
> 
> 
> 



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