From: "Sjur Brændeland" <sjurbren@gmail.com>
To: "Michael S. Tsirkin" <mst@redhat.com>,
Rusty Russell <rusty@rustcorp.com.au>,
Ohad Ben-Cohen <ohad@wizery.com>
Cc: "Amit Shah" <amit.shah@redhat.com>,
linux-kernel@vger.kernel.org,
"Linus Walleij" <linus.walleij@linaro.org>,
virtualization@lists.linux-foundation.org,
"Sjur Brændeland" <sjur.brandeland@stericsson.com>
Subject: Re: [RFC 1/2] virtio_console: Add support for DMA memory allocation
Date: Wed, 5 Sep 2012 20:15:36 +0200 [thread overview]
Message-ID: <CAJK669bhVfgnxuF6wVtdnzs2bgiJ2HzgwfWw4uZ=EqTdm43Jow@mail.gmail.com> (raw)
In-Reply-To: <20120905143558.GB10925@redhat.com>
Hi Michael.
>> If the device then asks for VIRTIO_CONSOLE_F_DMA_MEM
>> when DMA is not supported, virtio will do BUG_ON() from
>> virtio_check_driver_offered_feature().
>>
>> Is this acceptable or should we add a check in virtcons_probe()
>> and let the probing fail instead?
>>
>> E.g:
>> /* Refuse to bind if F_DMA_MEM request cannot be met */
>> if (!VIRTIO_CONSOLE_HAS_DMA &&
>> (vdev->config->get_features(vdev) & (1 << VIRTIO_CONSOLE_F_DMA_MEM))){
>> dev_err(&vdev->dev,
>> "DMA_MEM requested, but arch does not support DMA\n");
>> err = -EINVAL;
>> goto fail;
>> }
>>
>> Regards,
>> Sjur
>
> Failing probe would be cleaner. But there is still a problem:
> old driver will happily bind to that device and then
> fail to work, right?
Not just fail to work, the kernel will panic on the BUG_ON().
Remoteproc gets the virtio configuration from firmware loaded
from user space. So this type of problem might be triggered
for other virtio drivers as well.
> virtio pci has revision id for this, but remoteproc doesn't
> seem to have anything similar. Or did I miss it?
No there are currently no sanity check of
virtio type and feature bits in remoteproc.
One option may be to add this...
> If not -
> we probably need to use a different
> device id, and not a feature bit.
But if I create a new virtio console type, remoteproc
could still call the existing virtio_console with random
bad feature bits, causing kernel panic.
Even if we fix this particular problem, the general problem
still exists: bogus virtio declarations in remoteproc's firmware
may cause BUG_ON(). (Note the fundamental difference
between visualizations and remoteproc. For remoteproc
the virtio configuration comes from binaries loaded from
user space).
So maybe we should look for a more generic solution, e.g.
changing virtio probe functionality so that devices with
bad feature bits will not trigger BUG_ON(), but rather refuse
to bind the driver.
Regards,
Sjur
next prev parent reply other threads:[~2012-09-05 18:15 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-09-03 13:51 [RFC 1/2] virtio_console: Add support for DMA memory allocation sjur.brandeland
2012-09-03 13:51 ` [RFC 2/2] virtio_console: Add feature to disable console port sjur.brandeland
2012-09-03 14:30 ` [RFC 1/2] virtio_console: Add support for DMA memory allocation Michael S. Tsirkin
2012-09-03 14:57 ` Sjur Brændeland
2012-09-03 20:27 ` Michael S. Tsirkin
2012-09-04 6:07 ` Rusty Russell
2012-09-05 13:00 ` Sjur Brændeland
2012-09-05 14:35 ` Michael S. Tsirkin
2012-09-05 18:15 ` Sjur Brændeland [this message]
2012-09-05 19:16 ` Michael S. Tsirkin
2012-09-07 9:24 ` Sjur Brændeland
2012-09-04 11:28 ` Sjur Brændeland
2012-09-04 13:50 ` Michael S. Tsirkin
2012-09-04 16:58 ` Sjur Brændeland
2012-09-04 18:55 ` Michael S. Tsirkin
2012-09-06 2:04 ` Rusty Russell
2012-09-06 5:27 ` Michael S. Tsirkin
2012-09-10 22:11 ` Michael S. Tsirkin
2012-09-12 6:24 ` Rusty Russell
2012-09-07 8:35 ` Sjur Brændeland
2012-09-16 9:44 ` [PATCH repost] virtio: don't crash when device is buggy Michael S. Tsirkin
2012-09-17 4:27 ` Rusty Russell
2012-09-18 22:24 ` Michael S. Tsirkin
2012-09-19 4:10 ` Rusty Russell
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='CAJK669bhVfgnxuF6wVtdnzs2bgiJ2HzgwfWw4uZ=EqTdm43Jow@mail.gmail.com' \
--to=sjurbren@gmail.com \
--cc=amit.shah@redhat.com \
--cc=linus.walleij@linaro.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mst@redhat.com \
--cc=ohad@wizery.com \
--cc=rusty@rustcorp.com.au \
--cc=sjur.brandeland@stericsson.com \
--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).