Re: [Qemu-devel] [PATCH qemu] memory: Fix IOMMU replay base address

[David Gibson <david@gibson.dropbear.id.au>]

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On Tue, Feb 23, 2016 at 10:56:57AM +0100, Paolo Bonzini wrote:
> 
> 
> On 23/02/2016 10:00, Alexey Kardashevskiy wrote:
> >>>
> >>>           tce = tcet->table[addr >> tcet->page_shift];
> >>> -        ret.iova = addr & page_mask;
> >>> +        ret.iova = (addr + iommu->addr) & page_mask;
> >>>           ret.translated_addr = tce & page_mask;
> >>
> >> I wondered about that change, but I'd have to look closer to see if
> >> the iova field here is expected to be relative to the MR as well.  It
> >> would be oddly inconsistent if it wasn't.
> > 
> > It is relative and it does not make sense as there is no source MR/AS in
> > iotlb (only target AS) so there is no use in such iova.
> 
> ret.iova should be relative to the source AS (i.e. even if a 32-bit
> IOMMU region translates between 4GB and 8GB, ret.iova should have bits
> 32-63 set to 0).

Uh.. relative to the source AS, or the source MR?  At the moment spapr
implements it relative to the MR.. which seems to match your example.

> So there is a problem in vfio_iommu_map_notify:
> 
>         ret = vfio_dma_map(container, iotlb->iova,
>                            iotlb->addr_mask + 1, vaddr,
>                            !(iotlb->perm & IOMMU_WO) || mr->readonly);

Ah.. yeah.. this needs the address relative to the AS, not the MR

> I think that, in vfio_listener_region_add, the iova variable should be
> stored in VFIOGuestIOMMU for use in vfio_iommu_map_notify.

Hmm, seems a bit clunky, though I guess it's safe due to the BQL.

> ret.translated_addr should be relative to the target AS, which VFIO
> assumes to be address_space_memory.

Right, and as far as I can tell that is the case.

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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