[3.16.y-ckt stable] Patch "swiotlb-xen: remove BUG_ON in xen_bus_to_phys" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    swiotlb-xen: remove BUG_ON in xen_bus_to_phys

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From bc444778e0db5758beaacaf6f7536daa3e593e39 Mon Sep 17 00:00:00 2001
From: Stefano Stabellini <stefano.stabellini at eu.citrix.com>
Date: Fri, 21 Nov 2014 11:10:39 +0000
Subject: swiotlb-xen: remove BUG_ON in xen_bus_to_phys

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 at eu.citrix.com>
Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.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