net/xen-netback: disable on 64KB page granularity

Building the linux-3.16 stable branch, I ran into this warning that
shows a serious problem in the xen-netback driver:

drivers/net/xen-netback/netback.c: In function 'xenvif_dealloc_kthread':
drivers/net/xen-netback/netback.c:2002:1: error: the frame size of 16384 bytes is larger than 2048 bytes [-Werror=frame-larger-than=]

The bug was fixed in linux-4.4, but for any older stable kernel we
either need to backport that fix, or not use the driver when the page
size is set to 64KB. As the proper fix is way bigger than the usual limit
for stable backport patches, this adds a Kconfig dependency.

Fixes: d0089e8a0e4c ("net/xen-netback: Make it running on 64KB page granularity")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index 3fdfe317a6c54e078b69b699d39bf4e1eed7331d..b7e2fb72578da04e2efe51bdc2d6c63c47336da5 100644 (file)
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -331,6 +331,9 @@ config XEN_NETDEV_FRONTEND
 config XEN_NETDEV_BACKEND
        tristate "Xen backend network device"
        depends on XEN_BACKEND
+       depends on !(PAGE_SIZE_64KB || ARM64_64K_PAGES || \
+                    IA64_PAGE_SIZE_64KB || MICROBLAZE_64K_PAGES || \
+                    PARISC_PAGE_SIZE_64KB || PPC_64K_PAGES)
        help
          This driver allows the kernel to act as a Xen network driver
          domain which exports paravirtual network devices to other