From: Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
To: Shuah Khan <shuah.khan-VXdhtT5mjnY@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
stable <stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
shuahkhan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
Subject: Re: IO_PAGE_FAULTs on unity mapped regions during amd_iommu_init() in Linux 3.4
Date: Tue, 5 Feb 2013 14:31:05 +0100 [thread overview]
Message-ID: <20130205133104.GC2532@8bytes.org> (raw)
In-Reply-To: <1359743519.2759.38.camel@lorien2>
Hi Shuah,
On Fri, Feb 01, 2013 at 11:31:59AM -0700, Shuah Khan wrote:
> Yes, 3.7 has the same window of opportunity for this race condition,
> however I couldn't figure out why it doesn't happen on 3.7. On 3.7 the
> window between amd_iommu_init_hardware() and amd_iommu_init_dma_ops()
> might actually be wider than the window in 3.4.
I think this is highly timing related. IOMMU initialization may have
been moved by a few milliseconds between the kernel versions which might
cause the warnings to appear or disappear. I don't think it has much
value to dive deeper into the differences between the initialization
sequences.
As somethimes with such issues there is a simple and a more complex fix
for that. I'll try to come up with a simple fix for the next merge
window and implement the clean and more complex one for the next one.
Joerg
WARNING: multiple messages have this Message-ID (diff)
From: Joerg Roedel <joro@8bytes.org>
To: Shuah Khan <shuah.khan@hp.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
stable <stable@vger.kernel.org>,
iommu@lists.linux-foundation.org, shuahkhan@gmail.com
Subject: Re: IO_PAGE_FAULTs on unity mapped regions during amd_iommu_init() in Linux 3.4
Date: Tue, 5 Feb 2013 14:31:05 +0100 [thread overview]
Message-ID: <20130205133104.GC2532@8bytes.org> (raw)
In-Reply-To: <1359743519.2759.38.camel@lorien2>
Hi Shuah,
On Fri, Feb 01, 2013 at 11:31:59AM -0700, Shuah Khan wrote:
> Yes, 3.7 has the same window of opportunity for this race condition,
> however I couldn't figure out why it doesn't happen on 3.7. On 3.7 the
> window between amd_iommu_init_hardware() and amd_iommu_init_dma_ops()
> might actually be wider than the window in 3.4.
I think this is highly timing related. IOMMU initialization may have
been moved by a few milliseconds between the kernel versions which might
cause the warnings to appear or disappear. I don't think it has much
value to dive deeper into the differences between the initialization
sequences.
As somethimes with such issues there is a simple and a more complex fix
for that. I'll try to come up with a simple fix for the next merge
window and implement the clean and more complex one for the next one.
Joerg
next prev parent reply other threads:[~2013-02-05 13:31 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-31 18:33 IO_PAGE_FAULTs on unity mapped regions during amd_iommu_init() in Linux 3.4 Shuah Khan
2013-02-01 13:00 ` Joerg Roedel
2013-02-01 18:31 ` Shuah Khan
2013-02-05 13:31 ` Joerg Roedel [this message]
2013-02-05 13:31 ` Joerg Roedel
[not found] ` <20130205133104.GC2532-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
2013-02-05 13:57 ` Shuah Khan
2013-02-05 13:57 ` Shuah Khan
2013-02-06 12:12 ` Joerg Roedel
2013-02-07 2:40 ` Shuah Khan
2013-02-11 19:49 ` Greg KH
2013-02-11 19:49 ` Greg KH
[not found] ` <20130211194901.GA18115-U8xfFu+wG4EAvxtiuMwx3w@public.gmane.org>
2013-02-11 20:17 ` Shuah Khan
2013-02-11 20:17 ` Shuah Khan
2013-02-11 20:57 ` Shuah Khan
2013-02-11 22:18 ` Joerg Roedel
2013-02-11 22:18 ` Joerg Roedel
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=20130205133104.GC2532@8bytes.org \
--to=joro-zlv9swrftaidnm+yrofe0a@public.gmane.org \
--cc=iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org \
--cc=linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org \
--cc=shuah.khan-VXdhtT5mjnY@public.gmane.org \
--cc=shuahkhan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org \
--cc=stable-u79uwXL29TY76Z2rM5mHXA@public.gmane.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.