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[Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'?
From: |
Jintack Lim |
Subject: |
[Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'? |
Date: |
Tue, 20 Feb 2018 23:03:46 -0500 |
Hi,
I'm using vhost with the virtual intel-iommu, and this page[1] shows
the QEMU command line example.
qemu-system-x86_64 -M q35,accel=kvm,kernel-irqchip=split -m 2G \
-device intel-iommu,intremap=on,device-iotlb=on \
-device ioh3420,id=pcie.1,chassis=1 \
-device
virtio-net-pci,bus=pcie.1,netdev=net0,disable-legacy=on,disable-modern=off,iommu_platform=on,ats=on
\
-netdev tap,id=net0,vhostforce \
$IMAGE_PATH
I wonder what's the impact of using device-iotlb and ats options as
they are described necessary.
In my understanding, vhost in the kernel only looks at
VIRTIO_F_IOMMU_PLATFORM, and when it is set, vhost uses a
device-iotlb. In addition, vhost and QEMU communicate using vhost_msg
basically to cache mappings correctly in the vhost, so I wonder what's
the role of ats in this case.
A related question is that if we use SMMU emulation[2] on ARM without
those options, does vhost cache mappings as if it has a device-iotlb?
(I guess this is the case.)
I'm pretty new to QEMU code, so I might be missing something. Can
somebody shed some light on it?
[1] https://wiki.qemu.org/Features/VT-d
[2] http://lists.nongnu.org/archive/html/qemu-devel/2018-02/msg04736.html
Thanks,
Jintack
- [Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'?,
Jintack Lim <=
- Re: [Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'?, Peter Xu, 2018/02/22
- Re: [Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'?, Jintack Lim, 2018/02/23
- Re: [Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'?, Peter Xu, 2018/02/23
- Re: [Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'?, Jintack Lim, 2018/02/23
- Re: [Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'?, Peter Xu, 2018/02/23
- Re: [Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'?, Tian, Kevin, 2018/02/23
- Re: [Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'?, Jintack Lim, 2018/02/23
- Re: [Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'?, Jintack Lim, 2018/02/23
Re: [Qemu-devel] intel-iommu and vhost: Do we need 'device-iotlb' and 'ats'?, Auger Eric, 2018/02/26