target/ppc: Add ppc_hash64_filter_pagesizes()

The paravirtualized PAPR platform sometimes needs to restrict the guest to
using only some of the page sizes actually supported by the host's MMU.
At the moment this is handled in KVM specific code, but for consistency we
want to apply the same limitations to all accelerators.

This makes a start on this by providing a helper function in the cpu code
to allow platform code to remove some of the cpu's page size definitions
via a caller supplied callback.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Cédric Le Goater <clg@kaod.org>
Reviewed-by: Greg Kurz <groug@kaod.org>

target/ppc/mmu-hash64.c

@@ -1166,3 +1166,62 @@ const PPCHash64Options ppc_hash64_opts_POWER7 = {
         },
     }
 };
+
+void ppc_hash64_filter_pagesizes(PowerPCCPU *cpu,
+                                 bool (*cb)(void *, uint32_t, uint32_t),
+                                 void *opaque)
+{
+    PPCHash64Options *opts = cpu->hash64_opts;
+    int i;
+    int n = 0;
+    bool ci_largepage = false;
+
+    assert(opts);
+
+    n = 0;
+    for (i = 0; i < ARRAY_SIZE(opts->sps); i++) {
+        PPCHash64SegmentPageSizes *sps = &opts->sps[i];
+        int j;
+        int m = 0;
+
+        assert(n <= i);
+
+        if (!sps->page_shift) {
+            break;
+        }
+
+        for (j = 0; j < ARRAY_SIZE(sps->enc); j++) {
+            PPCHash64PageSize *ps = &sps->enc[j];
+
+            assert(m <= j);
+            if (!ps->page_shift) {
+                break;
+            }
+
+            if (cb(opaque, sps->page_shift, ps->page_shift)) {
+                if (ps->page_shift >= 16) {
+                    ci_largepage = true;
+                }
+                sps->enc[m++] = *ps;
+            }
+        }
+
+        /* Clear rest of the row */
+        for (j = m; j < ARRAY_SIZE(sps->enc); j++) {
+            memset(&sps->enc[j], 0, sizeof(sps->enc[j]));
+        }
+
+        if (m) {
+            n++;
+        }
+    }
+
+    /* Clear the rest of the table */
+    for (i = n; i < ARRAY_SIZE(opts->sps); i++) {
+        memset(&opts->sps[i], 0, sizeof(opts->sps[i]));
+    }
+
+    if (!ci_largepage) {
+        opts->flags &= ~PPC_HASH64_CI_LARGEPAGE;
+    }
+}