pseries: Implement h_read hcall

This h_call is useful for DLPAR in future amongst other things. Given an index
it fetches the corresponding PTE stored in the htab.

Signed-off-by: Erlon Cruz <erlon.cruz@br.flextronics.com>
Acked-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Alexander Graf <agraf@suse.de>

hw/spapr_hcall.c

diff --git a/hw/spapr_hcall.c b/hw/spapr_hcall.c
index 7b89594..77c052f 100644
--- a/hw/spapr_hcall.c
+++ b/hw/spapr_hcall.c
@@ -323,6 +323,36 @@
     return H_SUCCESS;
 }
 
+static target_ulong h_read(PowerPCCPU *cpu, sPAPREnvironment *spapr,
+                           target_ulong opcode, target_ulong *args)
+{
+    CPUPPCState *env = &cpu->env;
+    target_ulong flags = args[0];
+    target_ulong pte_index = args[1];
+    uint8_t *hpte;
+    int i, ridx, n_entries = 1;
+
+    if ((pte_index * HASH_PTE_SIZE_64) & ~env->htab_mask) {
+        return H_PARAMETER;
+    }
+
+    if (flags & H_READ_4) {
+        /* Clear the two low order bits */
+        pte_index &= ~(3ULL);
+        n_entries = 4;
+    }
+
+    hpte = env->external_htab + (pte_index * HASH_PTE_SIZE_64);
+
+    for (i = 0, ridx = 0; i < n_entries; i++) {
+        args[ridx++] = ldq_p(hpte);
+        args[ridx++] = ldq_p(hpte + (HASH_PTE_SIZE_64/2));
+        hpte += HASH_PTE_SIZE_64;
+    }
+
+    return H_SUCCESS;
+}
+
 static target_ulong h_set_dabr(PowerPCCPU *cpu, sPAPREnvironment *spapr,
                                target_ulong opcode, target_ulong *args)
 {
@@ -710,6 +740,7 @@
     spapr_register_hypercall(H_ENTER, h_enter);
     spapr_register_hypercall(H_REMOVE, h_remove);
     spapr_register_hypercall(H_PROTECT, h_protect);
+    spapr_register_hypercall(H_READ, h_read);
 
     /* hcall-bulk */
     spapr_register_hypercall(H_BULK_REMOVE, h_bulk_remove);