From: "Michael S. Tsirkin" <mst@redhat.com>
To: Halil Pasic <pasic@linux.ibm.com>
Cc: Jason Wang <jasowang@redhat.com>,
qemu-devel@nongnu.org, qemu-stable@nongnu.org
Subject: Re: [PATCH V2] vhost: correctly turn on VIRTIO_F_IOMMU_PLATFORM
Date: Wed, 26 Feb 2020 11:52:26 -0500 [thread overview]
Message-ID: <20200226115009-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20200226163618.31aa86ed.pasic@linux.ibm.com>
On Wed, Feb 26, 2020 at 04:36:18PM +0100, Halil Pasic wrote:
> On Wed, 26 Feb 2020 08:37:13 -0500
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
> > On Wed, Feb 26, 2020 at 02:28:39PM +0100, Halil Pasic wrote:
> > > On Wed, 26 Feb 2020 17:43:57 +0800
> > > Jason Wang <jasowang@redhat.com> wrote:
> > >
> > > > We turn on device IOTLB via VIRTIO_F_IOMMU_PLATFORM unconditionally on
> > > > platform without IOMMU support. This can lead unnecessary IOTLB
> > > > transactions which will damage the performance.
> > > >
> > > > Fixing this by check whether the device is backed by IOMMU and disable
> > > > device IOTLB.
> > > >
> > > > Reported-by: Halil Pasic <pasic@linux.ibm.com>
> > > > Fixes: c471ad0e9bd46 ("vhost_net: device IOTLB support")
> > > > Cc: qemu-stable@nongnu.org
> > > > Signed-off-by: Jason Wang <jasowang@redhat.com>
> > >
> > > Tested-by: Halil Pasic <pasic@linux.ibm.com>
> > > Reviewed-by: Halil Pasic <pasic@linux.ibm.com>
> > >
> > > Thank you very much for fixing this! BTW as I mentioned before it
> > > fixes vhost-vsock with iommu_platform=on as well.
> >
> > Fixes as in improves performance?
>
> No, fixes like one does not get something like:
> qemu-system-s390x: vhost_set_features failed: Operation not supported (95)
> qemu-system-s390x: Error starting vhost: 95
> any more.
>
> Regards,
> Halil
>
> [..]
But can commit c471ad0e9bd46 actually boot a secure guest
where iommu_platform=on is required?
--
MST
next prev parent reply other threads:[~2020-02-26 16:53 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-26 9:43 [PATCH V2] vhost: correctly turn on VIRTIO_F_IOMMU_PLATFORM Jason Wang
2020-02-26 9:53 ` Michael S. Tsirkin
2020-02-26 10:17 ` Jason Wang
2020-02-26 11:44 ` Michael S. Tsirkin
2020-02-26 12:50 ` Halil Pasic
2020-02-26 12:55 ` Halil Pasic
2020-02-26 13:45 ` Michael S. Tsirkin
2020-02-26 13:28 ` Halil Pasic
2020-02-26 13:37 ` Michael S. Tsirkin
2020-02-26 15:36 ` Halil Pasic
2020-02-26 16:52 ` Michael S. Tsirkin [this message]
2020-02-27 13:02 ` Halil Pasic
2020-02-27 15:47 ` Michael S. Tsirkin
2020-03-03 14:44 ` Halil Pasic
2020-03-13 12:44 ` Halil Pasic
2020-03-13 15:29 ` Michael S. Tsirkin
2020-03-13 16:31 ` Peter Xu
2020-03-16 16:57 ` Halil Pasic
2020-03-16 17:31 ` Peter Xu
2020-03-16 17:19 ` Michael S. Tsirkin
2020-03-16 18:14 ` Peter Xu
2020-03-17 3:04 ` Jason Wang
2020-03-17 14:13 ` Peter Xu
2020-03-18 2:06 ` Jason Wang
2020-03-17 6:28 ` Michael S. Tsirkin
2020-03-17 14:39 ` Peter Xu
2020-03-17 14:55 ` Michael S. Tsirkin
2020-03-13 20:27 ` Brijesh Singh
2020-03-14 18:22 ` Michael S. Tsirkin
2020-02-27 20:36 ` Tom Lendacky
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