Merge tag 'kvm-s390-master-5.8-3' of git://git.kernel.org/pub/scm/linux/kernel/git/kvms390/linux into kvm-master

The current number of KVM_IRQCHIP_NUM_PINS results in an order 3
allocation (32kb) for each guest start/restart which can result in OOM
killer activity when kernel memory is fragmented enough.

This fix reduces the number of iopins as s390 doesn't use them, hence
reducing the memory footprint.

Author: bonzini

arch/s390/include/asm/kvm_host.h

@@ -31,12 +31,12 @@
 #define KVM_USER_MEM_SLOTS 32
 
 /*
- * These seem to be used for allocating ->chip in the routing table,
- * which we don't use. 4096 is an out-of-thin-air value. If we need
- * to look at ->chip later on, we'll need to revisit this.
+ * These seem to be used for allocating ->chip in the routing table, which we
+ * don't use. 1 is as small as we can get to reduce the needed memory. If we
+ * need to look at ->chip later on, we'll need to revisit this.
  */
 #define KVM_NR_IRQCHIPS 1
-#define KVM_IRQCHIP_NUM_PINS 4096
+#define KVM_IRQCHIP_NUM_PINS 1
 #define KVM_HALT_POLL_NS_DEFAULT 50000
 
 /* s390-specific vcpu->requests bit members */