s390x/kvm: legacy_s390_alloc() only supports one allocation

We always allocate at a fixed address, a second allocation can therefore
of course never work. We would simply overwrite mappings.

This can e.g. happen in s390_memory_init(), if trying to allocate more
than > 8TB. Let's just bail out, as there is no need for supporting it
(legacy handling for z/VM).

Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20180628113817.30814-2-david@redhat.com>
Reviewed-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
index 8bcd832123..a9d6d606df 100644
--- a/target/s390x/kvm.c
+++ b/target/s390x/kvm.c
@@ -752,12 +752,20 @@ int kvm_s390_mem_op(S390CPU *cpu, vaddr addr, uint8_t ar, void *hostbuf,
  */
 static void *legacy_s390_alloc(size_t size, uint64_t *align, bool shared)
 {
-    void *mem;
+    static void *mem;
+
+    if (mem) {
+        /* we only support one allocation, which is enough for initial ram */
+        return NULL;
+    }
 
     mem = mmap((void *) 0x800000000ULL, size,
                PROT_EXEC|PROT_READ|PROT_WRITE,
                MAP_SHARED | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
-    return mem == MAP_FAILED ? NULL : mem;
+    if (mem == MAP_FAILED) {
+        mem = NULL;
+    }
+    return mem;
 }
 
 static uint8_t const *sw_bp_inst;