linux-kernel - [PATCH 3.16.y-ckt 081/216] swiotlb-xen: remove BUG_ON in xen_bus_to

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Message-Id: <1421085933-32536-82-git-send-email-luis.henriques@canonical.com>
Date:	Mon, 12 Jan 2015 18:03:18 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 081/216] swiotlb-xen: remove BUG_ON in xen_bus_to_phys

3.16.7-ckt4 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Stefano Stabellini <stefano.stabellini@...citrix.com>

commit c884227eaae9936f8ecbde6e1387bccdab5f4e90 upstream.

On x86 truncation cannot occur because config XEN depends on X86_64 ||
(X86_32 && X86_PAE).

On ARM truncation can occur without CONFIG_ARM_LPAE, when the dma
operation involves foreign grants. However in that case the physical
address returned by xen_bus_to_phys is actually invalid (there is no mfn
to pfn tracking for foreign grants on ARM) and it is not used.

Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
Reviewed-by: Catalin Marinas <catalin.marinas@....com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Signed-off-by: Luis Henriques <luis.henriques@...onical.com>
---
 drivers/xen/swiotlb-xen.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index bc6fb0d24ad5..f21282da9876 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -96,8 +96,6 @@ static inline phys_addr_t xen_bus_to_phys(dma_addr_t baddr)
 	dma_addr_t dma = (dma_addr_t)pfn << PAGE_SHIFT;
 	phys_addr_t paddr = dma;
 
-	BUG_ON(paddr != dma); /* truncation has occurred, should never happen */
-
 	paddr |= baddr & ~PAGE_MASK;
 
 	return paddr;
-- 
2.1.4

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