Messages in this thread | | | Date | Wed, 12 Jul 2017 18:54:56 +0100 | From | Will Deacon <> | Subject | Re: [RFC 0/2] arm-smmu-v3 tlbi-on-map option |
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Hi Eric,
On Sun, Jul 09, 2017 at 05:15:01PM +0200, Eric Auger wrote: > This series adds a new tlbi-on-map option to the smmuv3 driver. > When set, the IO_PGTABLE_QUIRK_TLBI_ON_MAP quirk is applied for > LPAE tables and the smmuv3 driver sends TLB invalidations on map. > > This mode is useful when running the driver on a guest as it allows > the virtualizer to trap any change to the translation structures. > This is similar to the Intel vtd caching mode (CM). > > This is especially needed for VFIO integration integration where > guest mappings must be applied to the physical IOMMU. > > At the moment the option only is available for DT probing.
I'm really not a fan of this approach. If a virtual IOMMU implementation is advertising itself as an SMMUv3, then it should adhere to the SMMUv3 architecture and not require non-standard behaviour from the driver. If we're going to allow that, then we're better off going the extra mile and using a PV approach. Given that the the SMMU3 architecture does *not* require TLBI on map, then I don't think we should be quirking our behaviour in this way. The fact that you only have this implemented for DT is the canary in the coal mine imo.
Will
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