[PATCH v11 00/13] SMMUv3 Nested Stage Setup (IOMMU part)
Shameerali Kolothum Thodi
shameerali.kolothum.thodi at huawei.com
Wed May 13 15:57:58 UTC 2020
> -----Original Message-----
> From: Auger Eric [mailto:eric.auger at redhat.com]
> Sent: 13 May 2020 14:29
> To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi at huawei.com>;
> Zhangfei Gao <zhangfei.gao at linaro.org>; eric.auger.pro at gmail.com;
> iommu at lists.linux-foundation.org; linux-kernel at vger.kernel.org;
> kvm at vger.kernel.org; kvmarm at lists.cs.columbia.edu; will at kernel.org;
> joro at 8bytes.org; maz at kernel.org; robin.murphy at arm.com
> Cc: jean-philippe at linaro.org; alex.williamson at redhat.com;
> jacob.jun.pan at linux.intel.com; yi.l.liu at intel.com; peter.maydell at linaro.org;
> tn at semihalf.com; bbhushan2 at marvell.com
> Subject: Re: [PATCH v11 00/13] SMMUv3 Nested Stage Setup (IOMMU part)
> >>> Yes that's normal this series is not meant to support vSVM at this stage.
> >>> I intend to add the missing pieces during the next weeks.
> >> Thanks for that. I have made an attempt to add the vSVA based on
> >> your v10 + JPBs sva patches. The host kernel and Qemu changes can
> >> be found here.
> >> This basically adds multiple pasid support on top of your changes.
> >> I have done some basic sanity testing and we have some initial success
> >> with the zip vf dev on our D06 platform. Please note that the STALL event is
> >> not yet supported though, but works fine if we mlock() guest usr mem.
> > I have added STALL support for our vSVA prototype and it seems to be
> > working(on our hardware). I have updated the kernel and qemu branches
> > the same. I should warn you though that these are prototype code and I
> am pretty
> > much re-using the VFIO_IOMMU_SET_PASID_TABLE interface for almost
> > But thought of sharing, in case if it is useful somehow!.
> Thank you again for sharing the POC. I looked at the kernel and QEMU
> Here are some preliminary comments:
> - "arm-smmu-v3: Reset S2TTB while switching back from nested stage": as
> you mentionned S2TTB reset now is featured in v11
> - "arm-smmu-v3: Add support for multiple pasid in nested mode": I could
> easily integrate this into my series. Update the iommu api first and
> pass multiple CD info in a separate patch
> - "arm-smmu-v3: Add support to Invalidate CD": CD invalidation should be
> cascaded to host through the PASID cache invalidation uapi (no pb you
> warned us for the POC you simply used VFIO_IOMMU_SET_PASID_TABLE). I
> think I should add this support in my original series although it does
> not seem to trigger any issue up to now.
Agree. Cache invalidation uapi is a better interface for this. Also I don’t think
this matters for non-vsva cases as Guest kernel table/CD(pasid 0) will never
> - "arm-smmu-v3: Remove duplication of fault propagation". I understand
> the transcode is done somewhere else with SVA but we still need to do it
> if a single CD is used, right? I will review the SVA code to better
Hmm..not sure. Need to take another look to see whether we need a special
handling for single CD or not.
> - for the STALL response injection I would tend to use a new VFIO region
> for responses. At the moment there is a single VFIO region for reporting
> the fault.
Sure. That will be much cleaner and probably improve the context switch
latency. Another thing I noted with STALL is that pasid_valid flag needs to be
taken care in the SVA kernel path.
"iommu: Remove pasid validity check for STALL model page response msg"
Not sure this one is a proper way to handle this.
> On QEMU side:
> - I am currently working on 3.2 range invalidation support which is
> needed for DPDK/VFIO
> - While at it I will look at how to incrementally introduce some of the
> features you need in this series.
Thanks for taking a look at the POC.
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