s390: autodetect map private

By default qemu will use MAP_PRIVATE for guest pages. This will write
protect pages and thus break on s390 systems that dont support this feature.
Therefore qemu has a hack to always use MAP_SHARED for s390. But MAP_SHARED
has other problems (no dirty pages tracking, a lot more swap overhead etc.)
Newer systems allow the distinction via KVM_CAP_S390_COW. With this feature
qemu can use the standard qemu alloc if available, otherwise it will use
the old s390 hack.

Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Acked-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

1 files changed, 13 insertions, 0 deletions

diff --git a/kvm-all.c b/kvm-all.c
index f8e432841f..1016ca49b1 100644
--- a/kvm-all.c
+++ b/kvm-all.c
@@ -1655,6 +1655,19 @@ int kvm_allows_irq0_override(void)
     return !kvm_irqchip_in_kernel() || kvm_has_gsi_routing();
 }
 
+void *kvm_vmalloc(ram_addr_t size)
+{
+#ifdef TARGET_S390X
+    void *mem;
+
+    mem = kvm_arch_vmalloc(size);
+    if (mem) {
+        return mem;
+    }
+#endif
+    return qemu_vmalloc(size);
+}
+
 void kvm_setup_guest_memory(void *start, size_t size)
 {
     if (!kvm_has_sync_mmu()) {