From: Jason Wang <jasowang@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>, Tiwei Bie <tiwei.bie@intel.com>
Cc: qemu-devel@nongnu.org, virtio-dev@lists.oasis-open.org,
alex.williamson@redhat.com, pbonzini@redhat.com,
stefanha@redhat.com, cunming.liang@intel.com, dan.daly@intel.com,
jianfeng.tan@intel.com, zhihong.wang@intel.com,
xiao.w.wang@intel.com
Subject: Re: [Qemu-devel] [virtio-dev] Re: [PATCH v1 6/6] vhost-user: add VFIO based accelerators support
Date: Fri, 26 Jan 2018 11:41:27 +0800 [thread overview]
Message-ID: <28ab37d5-6cf6-866d-9167-e14e7441415f@redhat.com> (raw)
In-Reply-To: <20180126015553-mutt-send-email-mst@kernel.org>
On 2018年01月26日 07:59, Michael S. Tsirkin wrote:
>> The virtual IOMMU isn't supported by the accelerators for now.
>> Because vhost-user currently lacks of an efficient way to share
>> the IOMMU table in VM to vhost backend. That's why the software
>> implementation of virtual IOMMU support in vhost-user backend
>> can't support dynamic mapping well.
> What exactly is meant by that? vIOMMU seems to work for people,
> it's not that fast if you change mappings all the time,
> but e.g. dpdk within guest doesn't.
Yes, software implementation support dynamic mapping for sure. I think
the point is, current vhost-user backend can not program hardware IOMMU.
So it can not let hardware accelerator to cowork with software vIOMMU. I
think that's another call to implement the offloaded path inside qemu
which has complete support for vIOMMU co-operated VFIO.
Thanks
>
>> Once this problem is solved
>> in vhost-user, virtual IOMMU can be supported by accelerators
>> too, and the IOMMU feature bit checking in this patch can be
>> removed.
> Given it works with software backends right now, I suspect
> this will be up to you guys to address.
>
next prev parent reply other threads:[~2018-01-26 3:59 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-25 4:03 [Qemu-devel] [PATCH v1 0/6] Extend vhost-user to support VFIO based accelerators Tiwei Bie
2018-01-25 4:03 ` [Qemu-devel] [PATCH v1 1/6] vhost-user: support receiving file descriptors in slave_read Tiwei Bie
2018-01-25 4:03 ` [Qemu-devel] [PATCH v1 2/6] vhost-user: introduce shared vhost-user state Tiwei Bie
2018-01-25 4:03 ` [Qemu-devel] [PATCH v1 3/6] virtio: support adding sub-regions for notify region Tiwei Bie
2018-01-25 4:03 ` [Qemu-devel] [PATCH v1 4/6] vfio: support getting VFIOGroup from groupfd Tiwei Bie
2018-01-25 4:03 ` [Qemu-devel] [PATCH v1 5/6] vfio: remove DPRINTF() definition from vfio-common.h Tiwei Bie
2018-01-25 4:03 ` [Qemu-devel] [PATCH v1 6/6] vhost-user: add VFIO based accelerators support Tiwei Bie
2018-01-25 23:59 ` Michael S. Tsirkin
2018-01-26 3:41 ` Jason Wang [this message]
2018-01-26 5:57 ` [Qemu-devel] [virtio-dev] " Tiwei Bie
2018-02-04 21:49 ` Alexander Duyck
2018-02-07 16:43 ` Michael S. Tsirkin
2018-02-07 18:02 ` Alexander Duyck
2018-02-07 21:59 ` Michael S. Tsirkin
2018-02-05 17:47 ` [Qemu-devel] [virtio-dev] " Paolo Bonzini
2018-02-06 4:40 ` Tiwei Bie
2018-02-07 15:23 ` Paolo Bonzini
2018-01-25 14:22 ` [Qemu-devel] [PATCH v1 0/6] Extend vhost-user to support VFIO based accelerators Stefan Hajnoczi
2018-01-25 16:10 ` Liang, Cunming
2018-01-26 7:17 ` Stefan Hajnoczi
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