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RE: [PATCH v16 00/10] VIRTIO-IOMMU device
From: |
Tian, Kevin |
Subject: |
RE: [PATCH v16 00/10] VIRTIO-IOMMU device |
Date: |
Thu, 5 Mar 2020 07:42:44 +0000 |
> From: Jean-Philippe Brucker <address@hidden>
> Sent: Thursday, March 5, 2020 3:34 PM
>
> On Thu, Mar 05, 2020 at 02:56:20AM +0000, Tian, Kevin wrote:
> > > From: Jean-Philippe Brucker <address@hidden>
> > > Sent: Thursday, March 5, 2020 12:47 AM
> > >
> > [...]
> > > > >
> > > > > * We can't use DVM in nested mode unless the VMID is shared with
> the
> > > > > CPU. For that we'll need the host SMMU driver to hook into the KVM
> > > VMID
> > > > > allocator, just like we do for the ASID allocator. I haven't yet
> > > > > investigated how to do that. It's possible to do vSVA without DVM
> > > > > though, by sending all TLB invalidations through the SMMU command
> > > queue.
> > > > > "
> > >
> > > Hm we're already mandating DVM for host SVA, so I'd say mandate it for
> > > vSVA as well. We'd avoid a ton of context switches, especially for the zip
> > > accelerator which doesn't require ATC invalidations. The host needs to
> pin
> > > the VMID allocated by KVM and write it in the endpoint's STE.
> > >
> >
> > Curious... what is DVM and how is it related to SVA? Is it SMMU specific?
>
> Yes it stands for "Distributed Virtual Memory", an Arm interconnect
> protocol. When sharing a process address space, TLB invalidations from the
> CPU are broadcasted to the SMMU, so we don't have to send commands
> through
> the SMMU queue to invalidate IOTLBs. However ATCs from PCIe endpoints
> do
> not participate in DVM and still have to be invalidated by hand.
>
ah, got it. Thanks for explanation!
- Re: [PATCH v16 00/10] VIRTIO-IOMMU device, Zhangfei Gao, 2020/03/02
- Re: [PATCH v16 00/10] VIRTIO-IOMMU device, Auger Eric, 2020/03/03
- Re: [PATCH v16 00/10] VIRTIO-IOMMU device, Zhangfei Gao, 2020/03/04
- Re: [PATCH v16 00/10] VIRTIO-IOMMU device, Auger Eric, 2020/03/04
- Re: [PATCH v16 00/10] VIRTIO-IOMMU device, Jean-Philippe Brucker, 2020/03/04
- RE: [PATCH v16 00/10] VIRTIO-IOMMU device, Tian, Kevin, 2020/03/04
- Re: [PATCH v16 00/10] VIRTIO-IOMMU device, Jean-Philippe Brucker, 2020/03/05
- RE: [PATCH v16 00/10] VIRTIO-IOMMU device,
Tian, Kevin <=