linux-kernel - [PATCH 1/1] powerpc/pseries/iommu: Fix window size for direct mapping with pmem

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Message-Id: <20210420045404.438735-1-leobras.c@gmail.com>
Date:   Tue, 20 Apr 2021 01:54:04 -0300
From:   Leonardo Bras <leobras.c@...il.com>
To:     Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Leonardo Bras <leobras.c@...il.com>,
        Alexey Kardashevskiy <aik@...abs.ru>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/1] powerpc/pseries/iommu: Fix window size for direct mapping with pmem

As of today, if the DDW is big enough to fit (1 << MAX_PHYSMEM_BITS) it's
possible to use direct DMA mapping even with pmem region.

But, if that happens, the window size (len) is set to
(MAX_PHYSMEM_BITS - page_shift) instead of MAX_PHYSMEM_BITS, causing a
pagesize times smaller DDW to be created, being insufficient for correct
usage.

Fix this so the correct window size is used in this case.

Fixes: bf6e2d562bbc4("powerpc/dma: Fallback to dma_ops when persistent memory present")
Signed-off-by: Leonardo Bras <leobras.c@...il.com>
---
 arch/powerpc/platforms/pseries/iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/iommu.c b/arch/powerpc/platforms/pseries/iommu.c
index 9fc5217f0c8e..836cbbe0ecc5 100644
--- a/arch/powerpc/platforms/pseries/iommu.c
+++ b/arch/powerpc/platforms/pseries/iommu.c
@@ -1229,7 +1229,7 @@ static u64 enable_ddw(struct pci_dev *dev, struct device_node *pdn)
 	if (pmem_present) {
 		if (query.largest_available_block >=
 		    (1ULL << (MAX_PHYSMEM_BITS - page_shift)))
-			len = MAX_PHYSMEM_BITS - page_shift;
+			len = MAX_PHYSMEM_BITS;
 		else
 			dev_info(&dev->dev, "Skipping ibm,pmemory");
 	}
-- 
2.30.2