From: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Subject: s390/kdump: fix out-of-memory with PCI
Patch-mainline: never, fixed upstream with larger code rework
References: bsc#1182256 LTC#191375

Description:   s390/kdump: fix out-of-memory with PCI
Symptom:       The kdump kernel runs out of memory when allocating memory for
               PCI IOMMU bitmaps in zpci_dma_init_device().
Problem:       The kdump kernel does not properly restrict memory_end, which
               the PCI code uses to calculate the size of the IOMMU bitmap, and
               too much memory will be allocated.
Solution:      Properly restrict memory_end to the available memory of the
               kdump kernel (OLDMEM_SIZE), similar to how it would be done with
               a "mem=" kernel parameter.
               This was fixed inadvertently by an unrelated upstream commit
               73045a08cf55 ("s390: unify identity mapping limits handling").
               But that commit cannot easily be backported to distribution
               levels, so only the part that fixes this bug will be submitted.
Reproduction:  Try kdump on a system with large memory size and many PCI
               functions.


Signed-off-by: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 arch/s390/kernel/setup.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/arch/s390/kernel/setup.c
+++ b/arch/s390/kernel/setup.c
@@ -610,8 +610,10 @@ static struct notifier_block kdump_mem_n
 static void reserve_memory_end(void)
 {
 #ifdef CONFIG_CRASH_DUMP
-	if (ipl_info.type == IPL_TYPE_FCP_DUMP &&
-	    !OLDMEM_BASE && sclp.hsa_size) {
+	if (OLDMEM_BASE) {
+		memory_end = min(memory_end ?: OLDMEM_SIZE, OLDMEM_SIZE);
+		memory_end_set = 1;
+	} else if (ipl_info.type == IPL_TYPE_FCP_DUMP && sclp.hsa_size) {
 		memory_end = sclp.hsa_size;
 		memory_end &= PAGE_MASK;
 		memory_end_set = 1;