ppc: Generalize the kvmppc_get_clockfreq() function

Currently the kvmppc_get_clockfreq() function reads the host's clock
frequency from /proc/device-tree, which is useful to past to the guest
in KVM setups.  However, there are some other host properties
advertised in the device tree which can also be relevant to the
guests.

This patch, therefore, replaces kvmppc_get_clockfreq() which can
retrieve any named, single integer property from the host device
tree's CPU node.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>

target-ppc/kvm.c

@@ -650,37 +650,50 @@ static int kvmppc_find_cpu_dt(char *buf, int buf_len)
     return 0;
 }
 
-uint64_t kvmppc_get_clockfreq(void)
+/* Read a CPU node property from the host device tree that's a single
+ * integer (32-bit or 64-bit).  Returns 0 if anything goes wrong
+ * (can't find or open the property, or doesn't understand the
+ * format) */
+static uint64_t kvmppc_read_int_cpu_dt(const char *propname)
 {
-    char buf[512];
-    uint32_t tb[2];
+    char buf[PATH_MAX];
+    union {
+        uint32_t v32;
+        uint64_t v64;
+    } u;
     FILE *f;
     int len;
 
     if (kvmppc_find_cpu_dt(buf, sizeof(buf))) {
-        return 0;
+        return -1;
     }
 
-    strncat(buf, "/clock-frequency", sizeof(buf) - strlen(buf));
+    strncat(buf, "/", sizeof(buf) - strlen(buf));
+    strncat(buf, propname, sizeof(buf) - strlen(buf));
 
     f = fopen(buf, "rb");
     if (!f) {
         return -1;
     }
 
-    len = fread(tb, sizeof(tb[0]), 2, f);
+    len = fread(&u, 1, sizeof(u), f);
     fclose(f);
     switch (len) {
-    case 1:
-        /* freq is only a single cell */
-        return tb[0];
-    case 2:
-        return *(uint64_t*)tb;
+    case 4:
+        /* property is a 32-bit quantity */
+        return be32_to_cpu(u.v32);
+    case 8:
+        return be64_to_cpu(u.v64);
     }
 
     return 0;
 }
 
+uint64_t kvmppc_get_clockfreq(void)
+{
+    return kvmppc_read_int_cpu_dt("clock-frequency");
+}
+
 int kvmppc_get_hypercall(CPUState *env, uint8_t *buf, int buf_len)
 {
     uint32_t *hc = (uint32_t*)buf;