linux-kernel - Re: [PATCH] x86: always define DECLARE_PCI

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Date:	Fri, 28 Nov 2008 18:45:10 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jesse Barnes <jbarnes@...tuousgeek.org>
Cc:	Joerg Roedel <joerg.roedel@....com>,
	Ingo Molnar <mingo@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
	stable@...nel.org
Subject: Re: [PATCH] x86: always define DECLARE_PCI_UNMAP* macros


* Jesse Barnes <jbarnes@...tuousgeek.org> wrote:

> On Thursday, November 27, 2008 3:45 am Ingo Molnar wrote:
> > * Joerg Roedel <joerg.roedel@....com> wrote:
> > > Currently these macros evaluate to a no-op except the kernel is
> > > compiled with GART or Calgary support. But we also need these macros
> > > when we have SWIOTLB, VT-d or AMD IOMMU in the kernel. Since we
> > > always compile at least with SWIOTLB we can define these macros
> > > always. This patch is also for stable backport for the same reason
> > > the SWIOTLB default selection patch is.
> > >
> > > Cc: stable@...nel.org
> > > Signed-off-by: Joerg Roedel <joerg.roedel@....com>
> > > ---
> > >  arch/x86/include/asm/pci_64.h |   14 --------------
> > >  1 files changed, 0 insertions(+), 14 deletions(-)
> >
> > applied to tip/x86/urgent (for v2.6.28), as this is a DMA mapping 
> > bugfix for IOMMUs. If the AMD IOMMU is turned on in the .config but 
> > CONFIG_GART_IOMMU is off (a rare but possible combo), we'd leak on 
> > unmap and crash the box quickly.
> >
> > Jesse, is that path of upstream merge fine with you?
> 
> Yeah, that's fine with me.  OTOH removing config options generally 
> seems like a good idea too, so maybe this combination should just be 
> disallowed.  Or is there a good reason for this type of config?

well, it's an IOMMU driver, so it's a kernel sizing/configuration thing, 
in line with how we generally allow drivers - with no particular 
dependency between them.

	Ingo
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