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 08:45:44 -0500 [thread overview]
Message-ID: <20200226084423-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20200226135539.384489f7.pasic@linux.ibm.com>
On Wed, Feb 26, 2020 at 01:55:39PM +0100, Halil Pasic wrote:
> On Wed, 26 Feb 2020 04:53:33 -0500
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
> > On Wed, Feb 26, 2020 at 05:43:57PM +0800, Jason Wang 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")
> >
> > Well it's just an optimization, isn't it?
> > I don't think it's justified to push this to everyone using
> > vhost with IOTLB, is it?
>
> IMHO we need this for everyone using vhost! For instance vhost-vsock
> currently does not work with iommu_platform=on, because unlike vhost-net
> vhost does not offer F_ACCESS_PLATFORM, so set features IOCTL fails.
You mean vsock does not offer it? OK but that's still not a bugfix.
Making new configs work is great, but that's a feature almost
by definition.
> > If you disagree, could you comment a bit on which configurations where tested?
> >
> > > Cc: qemu-stable@nongnu.org
> > > Signed-off-by: Jason Wang <jasowang@redhat.com>
> >
> > Halil could you test this pls? Does this help your performance issue?
> >
>
> I'm pretty sure it does, but I will re-test. The previous version where
> it was done virtio-net certainly did.
>
> Regards,
> Halil
>
>
next prev parent reply other threads:[~2020-02-26 13:46 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 [this message]
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
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
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20200226084423-mutt-send-email-mst@kernel.org \
--to=mst@redhat.com \
--cc=jasowang@redhat.com \
--cc=pasic@linux.ibm.com \
--cc=qemu-devel@nongnu.org \
--cc=qemu-stable@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.