linux-kernel - [PATCH 3.18 012/150] swiotlb-xen: remove BUG_ON in xen_bus_to

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Message-Id: <20150114072056.422114928@linuxfoundation.org>
Date:	Tue, 13 Jan 2015 23:21:23 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Catalin Marinas <catalin.marinas@....com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: [PATCH 3.18 012/150] swiotlb-xen: remove BUG_ON in xen_bus_to_phys

3.18-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: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/xen/swiotlb-xen.c |    2 --
 1 file changed, 2 deletions(-)

--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -96,8 +96,6 @@ static inline phys_addr_t xen_bus_to_phy
 	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;


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