s390/pci: enforce fmb page boundary rule

commit 80c544de 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: d0b08853 ("s390/pci: performance statistics and debug infrastructure")
Signed-off-by: Sebastian Ott <sebott@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

arch/s390/include/asm/pci.h

@@ -45,7 +45,7 @@ struct zpci_fmb {
 	u64 rpcit_ops;
 	u64 dma_rbytes;
 	u64 dma_wbytes;
-} __packed __aligned(16);
+} __packed __aligned(64);
 
 enum zpci_state {
 	ZPCI_FN_STATE_RESERVED,

arch/s390/pci/pci.c

@@ -871,8 +871,11 @@ 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;