From: "Michael S. Tsirkin" <mst@redhat.com>
To: Halil Pasic <pasic@linux.ibm.com>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
Jason Wang <jasowang@redhat.com>,
Cornelia Huck <cohuck@redhat.com>,
virtualization@lists.linux-foundation.org
Subject: Re: [PATCH] virtio: acknowledge all features before access
Date: Tue, 18 Jan 2022 10:11:23 -0500 [thread overview]
Message-ID: <20220118101010-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20220118134855.3e8cbce5.pasic@linux.ibm.com>
On Tue, Jan 18, 2022 at 01:48:55PM +0100, Halil Pasic wrote:
> On Fri, 14 Jan 2022 15:09:14 -0500
> "Michael S. Tsirkin" <mst@redhat.com> wrote:
>
> > The feature negotiation was designed in a way that
> > makes it possible for devices to know which config
> > fields will be accessed by drivers.
> >
> > This is broken since commit 404123c2db79 ("virtio: allow drivers to
> > validate features") with fallout in at least block and net.
> > We have a partial work-around in commit 2f9a174f918e ("virtio: write
> > back F_VERSION_1 before validate") which at least lets devices
> > find out which format should config space have, but this
> > is a partial fix: guests should not access config space
> > without acknowledging features since otherwise we'll never
> > be able to change the config space format.
> >
> > As a side effect, this also reduces the amount of hypervisor accesses -
> > we now only acknowledge features once unless we are clearing any
> > features when validating.
> >
> > Cc: stable@vger.kernel.org
> > Fixes: 404123c2db79 ("virtio: allow drivers to validate features")
> > Fixes: 2f9a174f918e ("virtio: write back F_VERSION_1 before validate")
> > Cc: "Halil Pasic" <pasic@linux.ibm.com>
> > Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
> > ---
> >
> > Halil, I thought hard about our situation with transitional and
> > today I finally thought of something I am happy with.
> > Pls let me know what you think. Testing on big endian would
> > also be much appreciated!
>
> Hi Michael!
>
> I was just about to have a look into this. But it does not apply
> cleanly to Linus master (fetched a couple of minutes ago). I also tride
> with d9679d0013a66849~1 but no luck. What is a suitable base for this
> patch?
>
> Regards,
> Halil
It's on top of
virtio: unexport virtio_finalize_features
You can also get
commit cc1f7f0bb64302c1153aa9337db970e6360b379d (HEAD, kernel.org/vhost, kernel.org/linux-next)
from my tree.
>
> > drivers/virtio/virtio.c | 31 +++++++++++++++++--------------
> > 1 file changed, 17 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c
> > index d891b0a354b0..2ed6e2451fd8 100644
> > --- a/drivers/virtio/virtio.c
> > +++ b/drivers/virtio/virtio.c
> > @@ -168,12 +168,10 @@ EXPORT_SYMBOL_GPL(virtio_add_status);
> >
> > static int virtio_finalize_features(struct virtio_device *dev)
> > {
> > - int ret = dev->config->finalize_features(dev);
> > unsigned status;
> > + int ret;
> >
> > might_sleep();
> > - if (ret)
> > - return ret;
> >
> > ret = arch_has_restricted_virtio_memory_access();
> > if (ret) {
> > @@ -244,17 +242,6 @@ static int virtio_dev_probe(struct device *_d)
> > driver_features_legacy = driver_features;
> > }
> >
> > - /*
> > - * Some devices detect legacy solely via F_VERSION_1. Write
> > - * F_VERSION_1 to force LE config space accesses before FEATURES_OK for
> > - * these when needed.
> > - */
> > - if (drv->validate && !virtio_legacy_is_little_endian()
> > - && device_features & BIT_ULL(VIRTIO_F_VERSION_1)) {
> > - dev->features = BIT_ULL(VIRTIO_F_VERSION_1);
> > - dev->config->finalize_features(dev);
> > - }
> > -
> > if (device_features & (1ULL << VIRTIO_F_VERSION_1))
> > dev->features = driver_features & device_features;
> > else
> > @@ -265,10 +252,22 @@ static int virtio_dev_probe(struct device *_d)
> > if (device_features & (1ULL << i))
> > __virtio_set_bit(dev, i);
> >
> > + err = dev->config->finalize_features(dev);
> > + if (err)
> > + goto err;
> > +
> > if (drv->validate) {
> > + u64 features = dev->features;
> > +
> > err = drv->validate(dev);
> > if (err)
> > goto err;
> > +
> > + if (features != dev->features) {
> > + err = dev->config->finalize_features(dev);
> > + if (err)
> > + goto err;
> > + }
> > }
> >
> > err = virtio_finalize_features(dev);
> > @@ -495,6 +494,10 @@ int virtio_device_restore(struct virtio_device *dev)
> > /* We have a driver! */
> > virtio_add_status(dev, VIRTIO_CONFIG_S_DRIVER);
> >
> > + ret = dev->config->finalize_features(dev);
> > + if (ret)
> > + goto err;
> > +
> > ret = virtio_finalize_features(dev);
> > if (ret)
> > goto err;
next prev parent reply other threads:[~2022-01-18 15:11 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-14 20:09 [PATCH] virtio: acknowledge all features before access Michael S. Tsirkin
2022-01-17 6:31 ` Jason Wang
2022-01-17 8:26 ` Michael S. Tsirkin
2022-01-17 12:38 ` Cornelia Huck
2022-01-17 23:13 ` Michael S. Tsirkin
2022-01-18 15:43 ` Michael S. Tsirkin
2022-01-18 17:10 ` Cornelia Huck
2022-01-18 12:48 ` Halil Pasic
2022-01-18 15:11 ` Michael S. Tsirkin [this message]
2022-01-18 14:43 ` Halil Pasic
2022-01-18 15:20 ` Michael S. Tsirkin
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=20220118101010-mutt-send-email-mst@kernel.org \
--to=mst@redhat.com \
--cc=cohuck@redhat.com \
--cc=jasowang@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=pasic@linux.ibm.com \
--cc=stable@vger.kernel.org \
--cc=virtualization@lists.linux-foundation.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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).