From: Avi Kivity <avi@scylladb.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Alex Williamson <alex.williamson@redhat.com>,
Vlad Zolotarov <vladz@cloudius-systems.com>,
Greg KH <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, hjk@hansjkoch.de, corbet@lwn.net,
bruce.richardson@intel.com, avi@cloudius-systems.com,
gleb@cloudius-systems.com, stephen@networkplumber.org,
alexander.duyck@gmail.com
Subject: Re: [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support
Date: Thu, 8 Oct 2015 12:44:09 +0300 [thread overview]
Message-ID: <56163AE9.6020000@scylladb.com> (raw)
In-Reply-To: <20151008114841-mutt-send-email-mst@redhat.com>
On 10/08/2015 12:16 PM, Michael S. Tsirkin wrote:
> On Thu, Oct 08, 2015 at 11:46:30AM +0300, Avi Kivity wrote:
>>
>> On 10/08/2015 10:32 AM, Michael S. Tsirkin wrote:
>>> On Thu, Oct 08, 2015 at 08:33:45AM +0300, Avi Kivity wrote:
>>>> It is good practice to defend against root oopsing the kernel, but in some
>>>> cases it cannot be achieved.
>>> Absolutely. That's one of the issues with these patches. They don't even
>>> try where it's absolutely possible.
>>>
>> Are you referring to blocking the maps of the msix BAR areas?
> For example. There are more. I listed some of the issues on the mailing
> list, and I might have missed some. VFIO has code to address all this,
> people should share code to avoid duplication, or at least read it
> to understand the issues.
All but one of those are unrelated to the patch that adds msix support.
>
>> I think there is value in that. The value is small because a
>> corruption is more likely in the dynamic memory responsible for tens
>> of millions of DMA operations per second, rather than a static 4K
>> area, but it exists.
> There are other bugs which will hurt e.g. each time application does not
> exit gracefully.
uio_pci_generic disables DMA when the device is removed, so we're safe
here, at least if files are released before the address space.
>
> But well, heh :) That's precisely my feeling about the whole "running
> userspace drivers without an IOMMU" project. The value is small
> since modern hardware has fast IOMMUs, but it exists.
>
For users that don't have iommus at all (usually because it is taken by
the hypervisor), it has great value.
I can't comment on iommu overhead; for my use case it is likely
negligible and we will use an iommu when available; but apparently it
matters for others.
next prev parent reply other threads:[~2015-10-08 9:44 UTC|newest]
Thread overview: 96+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-04 20:43 [PATCH v3 0/3] uio: add MSI/MSI-X support to uio_pci_generic driver Vlad Zolotarov
2015-10-04 20:43 ` [PATCH v3 1/3] uio: add ioctl support Vlad Zolotarov
2015-10-05 3:03 ` Greg KH
2015-10-05 7:33 ` Vlad Zolotarov
2015-10-05 8:01 ` Greg KH
2015-10-05 10:36 ` Vlad Zolotarov
2015-10-05 20:02 ` Michael S. Tsirkin
[not found] ` <CAOYyTHZ2=UCYxuJKvd5S6qxp=84DBq5bMadg5wL0rFLZBh2-8Q@mail.gmail.com>
2015-10-05 22:29 ` Michael S. Tsirkin
2015-10-06 8:33 ` Vlad Zolotarov
2015-10-06 14:19 ` Michael S. Tsirkin
2015-10-06 14:30 ` Gleb Natapov
2015-10-06 15:19 ` Michael S. Tsirkin
2015-10-06 15:31 ` Vlad Zolotarov
2015-10-06 15:57 ` Gleb Natapov
2015-10-04 20:43 ` [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov
2015-10-05 3:11 ` Greg KH
2015-10-05 7:41 ` Vlad Zolotarov
2015-10-05 7:56 ` Greg KH
2015-10-05 10:48 ` Vlad Zolotarov
2015-10-05 10:57 ` Greg KH
2015-10-05 11:09 ` Avi Kivity
2015-10-05 13:08 ` Greg KH
2015-10-05 11:41 ` Vlad Zolotarov
2015-10-05 11:47 ` Avi Kivity
2015-10-05 11:53 ` Vlad Zolotarov
2015-10-05 8:28 ` Avi Kivity
2015-10-05 9:49 ` Greg KH
2015-10-05 10:20 ` Avi Kivity
2015-10-06 14:38 ` Michael S. Tsirkin
2015-10-06 14:43 ` Vlad Zolotarov
2015-10-06 14:56 ` Michael S. Tsirkin
2015-10-06 15:23 ` Avi Kivity
2015-10-06 18:51 ` Alex Williamson
2015-10-06 21:32 ` Stephen Hemminger
2015-10-06 21:41 ` Alex Williamson
[not found] ` <CAOaVG152OrQz-Bbnpr0VeE+vLH7nMGsG6A3sD7eTQHormNGVUg@mail.gmail.com>
2015-10-07 7:57 ` Vlad Zolotarov
[not found] ` <5614C160.6000203@scylladb.com>
2015-10-07 8:00 ` Vlad Zolotarov
2015-10-07 8:01 ` Vlad Zolotarov
2015-10-07 6:52 ` Avi Kivity
2015-10-07 16:31 ` Alex Williamson
2015-10-07 16:39 ` Avi Kivity
2015-10-07 21:05 ` Michael S. Tsirkin
2015-10-08 4:19 ` Gleb Natapov
2015-10-08 7:41 ` Michael S. Tsirkin
2015-10-08 7:59 ` Gleb Natapov
2015-10-08 9:38 ` Michael S. Tsirkin
2015-10-08 9:45 ` Gleb Natapov
2015-10-08 12:15 ` Michael S. Tsirkin
2015-10-08 5:33 ` Avi Kivity
2015-10-08 7:32 ` Michael S. Tsirkin
2015-10-08 8:46 ` Avi Kivity
2015-10-08 9:16 ` Michael S. Tsirkin
2015-10-08 9:44 ` Avi Kivity [this message]
2015-10-08 12:06 ` Michael S. Tsirkin
2015-10-08 12:27 ` Gleb Natapov
2015-10-08 13:20 ` Michael S. Tsirkin
2015-10-08 13:28 ` Gleb Natapov
2015-10-08 16:43 ` Michael S. Tsirkin
2015-10-08 17:01 ` Gleb Natapov
2015-10-08 17:39 ` Michael S. Tsirkin
2015-10-08 17:53 ` Gleb Natapov
2015-10-08 18:38 ` Greg KH
2015-10-08 8:32 ` Michael S. Tsirkin
2015-10-08 8:52 ` Gleb Natapov
2015-10-08 9:19 ` Avi Kivity
2015-10-08 10:26 ` Michael S. Tsirkin
2015-10-08 13:20 ` Avi Kivity
2015-10-08 14:17 ` Michael S. Tsirkin
2015-10-08 15:31 ` Alex Williamson
2015-10-07 20:05 ` Michael S. Tsirkin
2015-10-07 7:55 ` Vlad Zolotarov
2015-10-08 8:48 ` Michael S. Tsirkin
2015-10-06 15:28 ` Vlad Zolotarov
2015-10-06 14:46 ` Michael S. Tsirkin
2015-10-06 15:27 ` Avi Kivity
2015-10-05 8:41 ` Stephen Hemminger
2015-10-05 9:08 ` Vlad Zolotarov
2015-10-05 10:06 ` Vlad Zolotarov
2015-10-05 20:09 ` Michael S. Tsirkin
2015-10-05 9:11 ` Vlad Zolotarov
2015-10-05 19:16 ` Michael S. Tsirkin
2015-10-04 20:43 ` [PATCH v3 3/3] Documentation: update uio-howto Vlad Zolotarov
2015-10-04 20:45 ` [PATCH v3 0/3] uio: add MSI/MSI-X support to uio_pci_generic driver Vlad Zolotarov
2015-10-05 19:50 ` Michael S. Tsirkin
2015-10-06 8:37 ` Vlad Zolotarov
2015-10-06 14:30 ` Michael S. Tsirkin
2015-10-06 14:40 ` Vlad Zolotarov
2015-10-06 15:13 ` Michael S. Tsirkin
2015-10-06 16:35 ` Vlad Zolotarov
2015-10-06 15:11 ` Avi Kivity
2015-10-06 15:15 ` Michael S. Tsirkin
2015-10-06 16:00 ` Gleb Natapov
2015-10-06 16:09 ` Avi Kivity
2015-10-07 10:25 ` Michael S. Tsirkin
2015-10-07 10:28 ` Avi Kivity
-- strict thread matches above, loose matches on Subject: below --
2015-10-04 20:39 Vlad Zolotarov
2015-10-04 20:39 ` [PATCH v3 2/3] uio_pci_generic: add MSI/MSI-X support Vlad Zolotarov
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