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#1182257 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/boot/ipl_parm.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/arch/s390/boot/ipl_parm.c
+++ b/arch/s390/boot/ipl_parm.c
@@ -243,6 +243,8 @@ void setup_memory_end(void)
 #ifdef CONFIG_CRASH_DUMP
 	if (OLDMEM_BASE) {
 		kaslr_enabled = 0;
+		memory_end = min(memory_end ?: OLDMEM_SIZE, OLDMEM_SIZE);
+		memory_end_set = 1;
 	} else if (ipl_block_valid &&
 		   ipl_block.pb0_hdr.pbt == IPL_PBT_FCP &&
 		   ipl_block.fcp.opt == IPL_PB0_FCP_OPT_DUMP) {