linux-kernel - [PATCH v2 07/13] powerpc/powernv: Do not set "read" flag if direction==DMA

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Date:	Tue, 23 Sep 2014 13:00:56 +1000
From:	Alexey Kardashevskiy <aik@...abs.ru>
To:	linuxppc-dev@...ts.ozlabs.org
Cc:	Alexey Kardashevskiy <aik@...abs.ru>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Alex Williamson <alex.williamson@...hat.com>,
	Gavin Shan <gwshan@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: [PATCH v2 07/13] powerpc/powernv: Do not set "read" flag if direction==DMA_NONE

Normally a bitmap from the iommu_table is used to track what TCE entry
is in use. Since we are going to use iommu_table without its locks and
do xchg() instead, it becomes essential not to put bits which are not
implied in the direction flag.

Signed-off-by: Alexey Kardashevskiy <aik@...abs.ru>
---
 arch/powerpc/platforms/powernv/pci.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/platforms/powernv/pci.c b/arch/powerpc/platforms/powernv/pci.c
index deddcad..ab79e2d 100644
--- a/arch/powerpc/platforms/powernv/pci.c
+++ b/arch/powerpc/platforms/powernv/pci.c
@@ -628,10 +628,18 @@ static int pnv_tce_build(struct iommu_table *tbl, long index, long npages,
 	__be64 *tcep, *tces;
 	u64 rpn;
 
-	proto_tce = TCE_PCI_READ; // Read allowed
-
-	if (direction != DMA_TO_DEVICE)
-		proto_tce |= TCE_PCI_WRITE;
+	switch (direction) {
+	case DMA_BIDIRECTIONAL:
+	case DMA_FROM_DEVICE:
+		proto_tce = TCE_PCI_READ | TCE_PCI_WRITE;
+		break;
+	case DMA_TO_DEVICE:
+		proto_tce = TCE_PCI_READ;
+		break;
+	default:
+		proto_tce = 0;
+		break;
+	}
 
 	tces = tcep = ((__be64 *)tbl->it_base) + index - tbl->it_offset;
 	rpn = __pa(uaddr) >> tbl->it_page_shift;
-- 
2.0.0

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