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Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support
From: |
Peter Xu |
Subject: |
Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support |
Date: |
Mon, 8 Feb 2021 13:26:07 -0500 |
Kevin,
On Mon, Feb 08, 2021 at 07:03:08AM +0000, Tian, Kevin wrote:
> It really depends on the definition of dev-iotlb in this context. To me the
> fact that virtio-iommu needs to notify the kernel for updating split cache
> is already sort of dev-iotlb semantics, regardless of whether it's delivered
> through a iotlb message or dev-iotlb message in a specific implementation. 😊
Yeah maybe it turns out that we'll just need to implement dev-iotlb for
virtio-iommu.
I am completely fine with that and I'm never against it. :) I was throwing out
a pure question only, because I don't know the answer.
My question was majorly based on the fact that dev-iotlb and iotlb messages
really look the same; it's not obvious then whether it would always matter a
lot when in a full emulation environment.
One example is current vhost - vhost previously would work without dev-iotlb
(ats=on) because trapping UNMAP would work too for vhost to work. It's also
simply because at least for VT-d the driver needs to send both one dev-iotlb
and one (probably same) iotlb message for a single page invalidation. The
dev-iotlb won't help a lot in full emulation here but instead it slows thing
down a little bit (QEMU has full knowledge as long as it receives either of the
message).
Thanks,
--
Peter Xu
- [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, 2021/02/07
- 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 <=
- 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
- Re: [PATCH] vhost: Unbreak SMMU and virtio-iommu on dev-iotlb support, Peter Xu, 2021/02/09