exec: simplify address_space_get_iotlb_entry

This patch let address_space_get_iotlb_entry() to use the newly
introduced page_mask parameter in flatview_do_translate(). Then we
will be sure the IOTLB can be aligned to page mask, also we should
nicely support huge pages now when introducing a764040c.

Fixes: a764040c ("exec: abstract address_space_do_translate()")
Signed-off-by: Peter Xu <peterx@redhat.com>
Signed-off-by: Maxime Coquelin <maxime.coquelin@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Message-Id: <20171010094247.10173-3-maxime.coquelin@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

exec.c

@@ -554,14 +554,14 @@ IOMMUTLBEntry address_space_get_iotlb_entry(AddressSpace *as, hwaddr addr,
                                             bool is_write)
 {
     MemoryRegionSection section;
-    hwaddr xlat, plen;
+    hwaddr xlat, page_mask;
 
-    /* Try to get maximum page mask during translation. */
-    plen = (hwaddr)-1;
-
-    /* This can never be MMIO. */
-    section = flatview_do_translate(address_space_to_flatview(as), addr,
-                                    &xlat, &plen, NULL, is_write, false, &as);
+    /*
+     * This can never be MMIO, and we don't really care about plen,
+     * but page mask.
+     */
+    section = flatview_do_translate(address_space_to_flatview(as), addr, &xlat,
+                                    NULL, &page_mask, is_write, false, &as);
 
     /* Illegal translation */
     if (section.mr == &io_mem_unassigned) {
@@ -572,22 +572,11 @@ IOMMUTLBEntry address_space_get_iotlb_entry(AddressSpace *as, hwaddr addr,
     xlat += section.offset_within_address_space -
         section.offset_within_region;
 
-    if (plen == (hwaddr)-1) {
-        /*
-         * We use default page size here. Logically it only happens
-         * for identity mappings.
-         */
-        plen = TARGET_PAGE_SIZE;
-    }
-
-    /* Convert to address mask */
-    plen -= 1;
-
     return (IOMMUTLBEntry) {
         .target_as = as,
-        .iova = addr & ~plen,
-        .translated_addr = xlat & ~plen,
-        .addr_mask = plen,
+        .iova = addr & ~page_mask,
+        .translated_addr = xlat & ~page_mask,
+        .addr_mask = page_mask,
         /* IOTLBs are for DMAs, and DMA only allows on RAMs. */
         .perm = IOMMU_RW,
     };