linux-kernel - Re: AMD Quad core - PCI-DMA: Out of IOMMU space on

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Date:	Tue, 17 Mar 2009 09:35:45 +0900
From:	FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
To:	mcgrof@...il.com
Cc:	linux-wireless@...r.kernel.org, joerg.roedel@....com,
	linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org
Subject: Re: AMD Quad core - PCI-DMA: Out of IOMMU space on > 4 GB RAM

On Mon, 16 Mar 2009 12:15:37 -0700
"Luis R. Rodriguez" <mcgrof@...il.com> wrote:

> I've run into "PCI-DMA: Out of IOMMU space" messages after loading and
> unloading a module 30 times. The interesting thing is this only
> happens if I have > 4 GB of memory. The box this occurs has AMD Phenom
> quad core CPU so I take it a harware IOMMU is being used. Below are
> example relevant messages with > 4 GB and then < 4 GB of memory. The
> driver I tested this with was ath9k. It could be an issue perhaps with
> ath9k but I am unable to find an issue in our probe/removal.
> 
> Could this be an issue with the AMD IOMMU used? Or is it more likely a
> driver issue?

ath9k wants DMA_32BIT_MASK, right? If so, GART IOMMU does nothing on a
system with < 4GB memory since ath9k can access to all the memory
addresses directly. With >4GB memory, GART needs to remap an address
higher than 4GB because ath9k wants DMA_32BIT_MASK.

>From a quick look, ath9k doesn't call pci_unmap_single for rx
buffers. Though I might be wrong because I don't know anything about
the driver.

=
From: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
Subject: [PATCH] ath9k: fix dma mapping leak of rx buffer

Signed-off-by: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>
---
 drivers/net/wireless/ath9k/recv.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/drivers/net/wireless/ath9k/recv.c b/drivers/net/wireless/ath9k/recv.c
index 462e08c..cd2a1f6 100644
--- a/drivers/net/wireless/ath9k/recv.c
+++ b/drivers/net/wireless/ath9k/recv.c
@@ -322,8 +322,11 @@ void ath_rx_cleanup(struct ath_softc *sc)
 
 	list_for_each_entry(bf, &sc->rx.rxbuf, list) {
 		skb = bf->bf_mpdu;
-		if (skb)
+		if (skb) {
+			pci_unmap_single(sc->pdev, bf->bf_buf_addr,
+					 sc->rx.bufsize, PCI_DMA_FROMDEVICE);
 			dev_kfree_skb(skb);
+		}
 	}
 
 	if (sc->rx.rxdma.dd_desc_len != 0)
-- 
1.6.0.6


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