linux-kernel - [PATCH] x86: fix iommu=nodac parameter handling

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Date:	Mon, 26 Oct 2009 15:41:46 +0100
From:	Tejun Heo <tj@...nel.org>
To:	the arch/x86 maintainers <x86@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>, "H. Peter Anvin" <hpa@...or.com>,
	athena@...w.org
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86: fix iommu=nodac parameter handling

nodac should forbid dac instead of enabling it.  Fix it.

Signed-off-by: Tejun Heo <tj@...nel.org>
Cc: Matteo Frigo <athena@...w.org>
Cc: stable@...nel.org
---
This was posted several months ago in a two patch series.  The second
one was rejected by Alan and with that the first one got lost too
although it's an apparent bug fix.  Matteo hit this bug recently and
reminded me about this patch.  So, regenerated and reposting.

Thanks.

 arch/x86/kernel/pci-dma.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/pci-dma.c b/arch/x86/kernel/pci-dma.c
index d20009b..8cf3996 100644
--- a/arch/x86/kernel/pci-dma.c
+++ b/arch/x86/kernel/pci-dma.c
@@ -216,7 +216,7 @@ static __init int iommu_setup(char *p)
 		if (!strncmp(p, "allowdac", 8))
 			forbid_dac = 0;
 		if (!strncmp(p, "nodac", 5))
-			forbid_dac = -1;
+			forbid_dac = 1;
 		if (!strncmp(p, "usedac", 6)) {
 			forbid_dac = -1;
 			return 1;
--
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