On 2020/10/30 下午6:54, Stefano Garzarella wrote:
On Fri, Oct 30, 2020 at 06:02:18PM +0800, Jason Wang wrote:
On 2020/10/30 上午1:43, Stefano Garzarella wrote:
This patch enables the IOTLB API support for vhost-vsock devices,
allowing the userspace to emulate an IOMMU for the guest.
These changes were made following vhost-net, in details this patch:
- exposes VIRTIO_F_ACCESS_PLATFORM feature and inits the iotlb
device if the feature is acked
- implements VHOST_GET_BACKEND_FEATURES and
VHOST_SET_BACKEND_FEATURES ioctls
- calls vq_meta_prefetch() before vq processing to prefetch vq
metadata address in IOTLB
- provides .read_iter, .write_iter, and .poll callbacks for the
chardev; they are used by the userspace to exchange IOTLB messages
This patch was tested with QEMU and a patch applied [1] to fix a
simple issue:
$ qemu -M q35,accel=kvm,kernel-irqchip=split \
-drive file=fedora.qcow2,format=qcow2,if=virtio \
-device intel-iommu,intremap=on \
-device vhost-vsock-pci,guest-cid=3,iommu_platform=on
Patch looks good, but a question:
It looks to me you don't enable ATS which means vhost won't get any
invalidation request or did I miss anything?
You're right, I didn't see invalidation requests, only miss and updates.
Now I have tried to enable 'ats' and 'device-iotlb' but I still don't
see any invalidation.
How can I test it? (Sorry but I don't have much experience yet with
vIOMMU)
I guess it's because the batched unmap. Maybe you can try to use
"intel_iommu=strict" in guest kernel command line to see if it works.
Btw, make sure the qemu contains the patch [1]. Otherwise ATS won't be
enabled for recent Linux Kernel in the guest.
Thanks
[1] https://patchew.org/QEMU/20200909081731.24688-1-jasowang@xxxxxxxxxx/
Thanks,
Stefano
