[PATCH 3.16 098/217] s390/pci: enforce fmb page boundary rule

[Ben Hutchings]

3.16.35-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Sebastian Ott <sebott@xxxxxxxxxxxxxxxxxx>

commit 80c544ded25ac14d7cc3e555abb8ed2c2da99b84 upstream.

The function measurement block must not cross a page boundary. Ensure
that by raising the alignment requirement to the smallest power of 2
larger than the size of the fmb.

Fixes: d0b088531 ("s390/pci: performance statistics and debug infrastructure")
Signed-off-by: Sebastian Ott <sebott@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Martin Schwidefsky <schwidefsky@xxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 arch/s390/include/asm/pci.h | 2 +-
 arch/s390/pci/pci.c         | 5 ++++-
 2 files changed, 5 insertions(+), 2 deletions(-)

--- a/arch/s390/include/asm/pci.h
+++ b/arch/s390/include/asm/pci.h
@@ -48,7 +48,7 @@ struct zpci_fmb {
 	atomic64_t allocated_pages;
 	atomic64_t mapped_pages;
 	atomic64_t unmapped_pages;
-} __packed __aligned(16);
+} __packed __aligned(64);
 
 #define ZPCI_MSI_VEC_BITS	11
 #define ZPCI_MSI_VEC_MAX	(1 << ZPCI_MSI_VEC_BITS)
--- a/arch/s390/pci/pci.c
+++ b/arch/s390/pci/pci.c
@@ -840,8 +840,11 @@ static inline int barsize(u8 size)
 
 static int zpci_mem_init(void)
 {
+	BUILD_BUG_ON(!is_power_of_2(__alignof__(struct zpci_fmb)) ||
+		     __alignof__(struct zpci_fmb) < sizeof(struct zpci_fmb));
+
 	zdev_fmb_cache = kmem_cache_create("PCI_FMB_cache", sizeof(struct zpci_fmb),
-				16, 0, NULL);
+					   __alignof__(struct zpci_fmb), 0, NULL);
 	if (!zdev_fmb_cache)
 		goto error_zdev;