From: Stefano Garzarella <sgarzare@redhat.com>
To: Jason Wang <jasowang@redhat.com>
Cc: mst@redhat.com, netdev@vger.kernel.org,
Stefan Hajnoczi <stefanha@redhat.com>,
kvm@vger.kernel.org, virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] vhost/vsock: add IOTLB API support
Date: Fri, 30 Oct 2020 17:19:38 +0100 [thread overview]
Message-ID: <20201030161938.n7xqeu557dmsqpzv@steredhat> (raw)
In-Reply-To: <278f4732-e561-2b4f-03ee-b26455760b01@redhat.com>
On Fri, Oct 30, 2020 at 07:44:43PM +0800, Jason Wang wrote:
>
>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.
>
I tried with "intel_iommu=strict" in the guest kernel and QEMU patch
applied, but I didn't see any invalidation.
Maybe I did something wrong, you know it is friday, KVM Forum is ending,
etc... ;-)
I'll investigate better next week.
Thanks for the useful info,
Stefano
next prev parent reply other threads:[~2020-10-30 16:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-29 17:43 [PATCH] vhost/vsock: add IOTLB API support Stefano Garzarella
2020-10-30 9:10 ` Stefan Hajnoczi
2020-10-30 10:02 ` Jason Wang
2020-10-30 10:54 ` Stefano Garzarella
2020-10-30 11:44 ` Jason Wang
2020-10-30 16:19 ` Stefano Garzarella [this message]
2020-11-02 17:11 ` Stefano Garzarella
2020-11-03 9:04 ` Jason Wang
2020-11-03 19:46 ` Peter Xu
2020-11-04 9:33 ` Stefano Garzarella
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