linux-kernel - Re: inode->i_wb

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Date:	Mon, 12 Mar 2012 21:27:15 +0000
From:	David Woodhouse <dwmw2@...radead.org>
To:	Josh Boyer <jwboyer@...hat.com>
Cc:	Keith Packard <keithp@...thp.com>, Dave Jones <davej@...hat.com>,
	Yang Bai <hamo.by@...il.com>,
	Fengguang Wu <fengguang.wu@...el.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Fedora Kernel Team <kernel-team@...oraproject.org>,
	kernel@...arici.cz
Subject: Re: inode->i_wb_list corruption.

On Mon, 2012-03-12 at 17:13 -0400, Josh Boyer wrote:
> On Fri, Mar 09, 2012 at 02:44:49PM -0800, Keith Packard wrote:
> > <#part sign=pgpmime>
> > On Fri, 9 Mar 2012 15:19:34 -0500, Josh Boyer <jwboyer@...hat.com> wrote:
> > 
> > > Is the VT-d issue something in the hardware itself, or do you mean if
> > > you have it enabled in the kernel?  We've had the intel IOMMU disabled
> > > by default in the Fedora kernels for a while now.  At least since before
> > > 3.2 was released.
> > 
> > I don't know for sure; David Woodhouse gave a scary presentation
> > yesterday that makes me unsure of what happens when IOMMU is disabled in
> > the kernel, given that much of the hardware is setup by the BIOS.
> 
> Is that presentation something that could be shared?  I have to say,
> hearing that doesn't really inspire confidence in either the IOMMU or
> the kernel.

It was mostly just a rant about the design mistakes we made with the
IOMMU — in particular giving the BIOS as much rope as possible for it to
hang us with.

If the BIOS exposes the IOMMU but the OS chooses not to enable it, I
don't believe there's any problem with that.

-- 
dwmw2

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