From: Halil Pasic <pasic@linux.ibm.com>
To: "Michael S. Tsirkin" <mst@redhat.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 13:55:39 +0100 [thread overview]
Message-ID: <20200226135539.384489f7.pasic@linux.ibm.com> (raw)
In-Reply-To: <20200226045128-mutt-send-email-mst@kernel.org>
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.
> 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 12:56 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 [this message]
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
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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