Re: [Qemu-devel] [RFC PATCH 06/10] vfio: Allow hotplug of containers onto existing guest IOMMU mappings

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

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On Wed, Sep 23, 2015 at 01:02:32PM +0200, Thomas Huth wrote:
> On 18/09/15 01:31, David Gibson wrote:
> > On Thu, Sep 17, 2015 at 10:54:24AM -0600, Alex Williamson wrote:
> >> On Thu, 2015-09-17 at 23:09 +1000, David Gibson wrote:
> >>> At present the memory listener used by vfio to keep host IOMMU mappings
> >>> in sync with the guest memory image assumes that if a guest IOMMU
> >>> appears, then it has no existing mappings.
> >>>
> >>> This may not be true if a VFIO device is hotplugged onto a guest bus
> >>> which didn't previously include a VFIO device, and which has existing
> >>> guest IOMMU mappings.
> >>>
> >>> Therefore, use the memory_region_register_iommu_notifier_replay()
> >>> function in order to fix this case, replaying existing guest IOMMU
> >>> mappings, bringing the host IOMMU into sync with the guest IOMMU.
> >>>
> >>> Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
> >>> ---
> >>>  hw/vfio/common.c | 34 +++++++++++++++++++---------------
> >>>  1 file changed, 19 insertions(+), 15 deletions(-)
> >>>
> >>> diff --git a/hw/vfio/common.c b/hw/vfio/common.c
> >>> index daaac48..543c38e 100644
> >>> --- a/hw/vfio/common.c
> >>> +++ b/hw/vfio/common.c
> >>> @@ -312,6 +312,22 @@ out:
> >>>      rcu_read_unlock();
> >>>  }
> >>>  
> >>> +static hwaddr vfio_container_granularity(VFIOContainer *container)
> >>> +{
> >>> +    uint64_t pgsize;
> >>> +
> >>> +    assert(container->iommu_data.iova_pgsizes);
> >>
> >> return (hwaddr)1 << (ffsl(container->iommu_data.iova_pgsizes) - 1;
> > 
> > Ah, yes, that should work.  I didn't do it that way mostly because I
> > tend to confuse myself when I try to remember exactly how ffs
> > semantics work.
> 
> Maybe use ffsll instead of ffsl, in case the code ever runs on a 32-bit
> host instead of a 64-bit host ?

Already done :)

-- 
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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