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From: Shuah Khan <shuahkhan@gmail.com>
To: Joerg Roedel <joro@8bytes.org>
Cc: Shuah Khan <shuah.khan@hp.com>,
	LKML <linux-kernel@vger.kernel.org>,
	stable <stable@vger.kernel.org>,
	iommu@lists.linux-foundation.org
Subject: Re: IO_PAGE_FAULTs on unity mapped regions during amd_iommu_init() in Linux 3.4
Date: Tue, 5 Feb 2013 06:57:21 -0700	[thread overview]
Message-ID: <CAKocOOO6Z2LyLYiuQMWf4iv4PAP8h5jbNWxRcSXKgXD1es6GYg@mail.gmail.com> (raw)
In-Reply-To: <20130205133104.GC2532@8bytes.org>

On Tue, Feb 5, 2013 at 6:31 AM, Joerg Roedel <joro@8bytes.org> wrote:
> 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.
>

Hi Joerg,

Thanks much. I will hang on to this test system for testing your fix.

-- Shuah

WARNING: multiple messages have this Message-ID (diff)
From: Shuah Khan <shuahkhan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
To: Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org,
	Shuah Khan <shuah.khan-VXdhtT5mjnY@public.gmane.org>,
	LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
	stable <stable-u79uwXL29TY76Z2rM5mHXA@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 06:57:21 -0700	[thread overview]
Message-ID: <CAKocOOO6Z2LyLYiuQMWf4iv4PAP8h5jbNWxRcSXKgXD1es6GYg@mail.gmail.com> (raw)
In-Reply-To: <20130205133104.GC2532-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>

On Tue, Feb 5, 2013 at 6:31 AM, Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org> wrote:
> 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.
>

Hi Joerg,

Thanks much. I will hang on to this test system for testing your fix.

-- Shuah

  reply	other threads:[~2013-02-05 13:57 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
2013-02-05 13:31       ` Joerg Roedel
2013-02-05 13:57       ` Shuah Khan [this message]
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
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

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