hw/block/nvme: refactor nvme_addr_read

Pull the controller memory buffer check to its own function. The check
will be used on its own in later patches.
Signed-off-by: NKlaus Jensen <k.jensen@samsung.com>
Reviewed-by: NPhilippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: NMaxim Levitsky <mlevitsk@redhat.com>
Reviewed-by: NKeith Busch <kbusch@kernel.org>
Message-Id: <20200609190333.59390-7-its@irrelevant.dk>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>

hw/block/nvme.c

@@ -65,14 +65,22 @@
 
 static void nvme_process_sq(void *opaque);
 
+static bool nvme_addr_is_cmb(NvmeCtrl *n, hwaddr addr)
+{
+    hwaddr low = n->ctrl_mem.addr;
+    hwaddr hi  = n->ctrl_mem.addr + int128_get64(n->ctrl_mem.size);
+
+    return addr >= low && addr < hi;
+}
+
 static void nvme_addr_read(NvmeCtrl *n, hwaddr addr, void *buf, int size)
 {
-    if (n->cmbsz && addr >= n->ctrl_mem.addr &&
-                addr < (n->ctrl_mem.addr + int128_get64(n->ctrl_mem.size))) {
+    if (n->cmbsz && nvme_addr_is_cmb(n, addr)) {
         memcpy(buf, (void *)&n->cmbuf[addr - n->ctrl_mem.addr], size);
-    } else {
-        pci_dma_read(&n->parent_obj, addr, buf, size);
+        return;
     }
+
+    pci_dma_read(&n->parent_obj, addr, buf, size);
 }
 
 static int nvme_check_sqid(NvmeCtrl *n, uint16_t sqid)