[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
RE: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support
From: |
Tian, Kevin |
Subject: |
RE: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support |
Date: |
Sun, 7 Feb 2021 09:04:55 +0000 |
> From: Peter Xu
> Sent: Friday, February 5, 2021 11:31 PM
>
> > >
> > >
> > >> or virtio-iommu
> > >> since dev-iotlb (or PCIe ATS)
> > >
> > >
> > > We may need to add this in the future.
> > added Jean-Philippe in CC
>
> So that's the part I'm unsure about.. Since everybody is cced so maybe good
> time to ask. :)
>
> The thing is I'm still not clear on whether dev-iotlb is useful for a full
> emulation environment and how that should differ from a normal iotlb, since
> after all normal iotlb will be attached with device information too.
dev-iotlb is useful in two manners. First, it's a functional prerequisite for
supporting I/O page faults. Second, it has performance benefit as you don't
need to contend the lock of global iotlb.
>
> For real hardwares, they make sense because they ask for two things: iotlb is
> for IOMMU, but dev-iotlb is for the device cache. For emulation
> environment
> (virtio-iommu is the case) do we really need that complexity?
>
> Note that even if there're assigned devices under virtio-iommu in the future,
> we can still isolate that and iiuc we can easily convert an iotlb (from
> virtio-iommu) into a hardware IOMMU dev-iotlb no matter what type of
> IOMMU is
> underneath the vIOMMU.
>
Didn't get this point. Hardware dev-iotlb is updated by hardware (between
the device and the IOMMU). How could software convert a virtual iotlb
entry into hardware dev-iotlb?
Thanks
Kevin
- [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Peter Xu, 2021/02/04
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Jason Wang, 2021/02/04
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Auger Eric, 2021/02/05
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Peter Xu, 2021/02/05
- RE: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support,
Tian, Kevin <=
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Peter Xu, 2021/02/07
- RE: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Tian, Kevin, 2021/02/08
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Peter Xu, 2021/02/08
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Jason Wang, 2021/02/09
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Auger Eric, 2021/02/08
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Jason Wang, 2021/02/07
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Peter Xu, 2021/02/08
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Auger Eric, 2021/02/08
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Jason Wang, 2021/02/08
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Auger Eric, 2021/02/09