diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 69ead4b34a..fe676b4831 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -574,9 +574,12 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
 
 Aml *aml_pci_device_dsm(void)
 {
-    Aml *method, *UUID, *ifctx, *ifctx1, *ifctx2, *ifctx3, *elsectx;
-    Aml *acpi_index = aml_local(0);
+    Aml *method, *UUID, *ifctx, *ifctx1;
+    Aml *ret = aml_local(0);
+    Aml *caps = aml_local(1);
+    Aml *acpi_index = aml_local(2);
     Aml *zero = aml_int(0);
+    Aml *one = aml_int(1);
     Aml *bnum = aml_arg(4);
     Aml *func = aml_arg(2);
     Aml *rev = aml_arg(1);
@@ -584,73 +587,85 @@ Aml *aml_pci_device_dsm(void)
 
     method = aml_method("PDSM", 6, AML_SERIALIZED);
 
+    /* get supported functions */
+    ifctx = aml_if(aml_equal(func, zero));
+    {
+        uint8_t byte_list[1] = { 0 }; /* nothing supported yet */
+        aml_append(ifctx, aml_store(aml_buffer(1, byte_list), ret));
+        aml_append(ifctx, aml_store(zero, caps));
+
+       /*
+        * PCI Firmware Specification 3.1
+        * 4.6.  _DSM Definitions for PCI
+        */
+        UUID = aml_touuid("E5C937D0-3553-4D7A-9117-EA4D19C3434D");
+        ifctx1 = aml_if(aml_lnot(aml_equal(aml_arg(0), UUID)));
+        {
+            /* call is for unsupported UUID, bail out */
+            aml_append(ifctx1, aml_return(ret));
+        }
+        aml_append(ifctx, ifctx1);
+
+        ifctx1 = aml_if(aml_lless(rev, aml_int(2)));
+        {
+            /* call is for unsupported REV, bail out */
+            aml_append(ifctx1, aml_return(ret));
+        }
+        aml_append(ifctx, ifctx1);
+
+        aml_append(ifctx,
+            aml_store(aml_call2("AIDX", bnum, sunum), acpi_index));
+        /*
+         * advertise function 7 if device has acpi-index
+         * acpi_index values:
+         *            0: not present (default value)
+         *     FFFFFFFF: not supported (old QEMU without PIDX reg)
+         *        other: device's acpi-index
+         */
+        ifctx1 = aml_if(aml_lnot(
+                     aml_or(aml_equal(acpi_index, zero),
+                            aml_equal(acpi_index, aml_int(0xFFFFFFFF)), NULL)
+                 ));
+        {
+            /* have supported functions */
+            aml_append(ifctx1, aml_or(caps, one, caps));
+            /* support for function 7 */
+            aml_append(ifctx1,
+                aml_or(caps, aml_shiftleft(one, aml_int(7)), caps));
+        }
+        aml_append(ifctx, ifctx1);
+
+        aml_append(ifctx, aml_store(caps, aml_index(ret, zero)));
+        aml_append(ifctx, aml_return(ret));
+    }
+    aml_append(method, ifctx);
+
+    /* handle specific functions requests */
     /*
      * PCI Firmware Specification 3.1
-     * 4.6.  _DSM Definitions for PCI
+     * 4.6.7. _DSM for Naming a PCI or PCI Express Device Under
+     *        Operating Systems
      */
-    UUID = aml_touuid("E5C937D0-3553-4D7A-9117-EA4D19C3434D");
-    ifctx = aml_if(aml_equal(aml_arg(0), UUID));
+    ifctx = aml_if(aml_equal(func, aml_int(7)));
     {
-        aml_append(ifctx, aml_store(aml_call2("AIDX", bnum, sunum), acpi_index));
-        ifctx1 = aml_if(aml_equal(func, zero));
-        {
-            uint8_t byte_list[1];
+       Aml *pkg = aml_package(2);
 
-            ifctx2 = aml_if(aml_equal(rev, aml_int(2)));
-            {
-                /*
-                 * advertise function 7 if device has acpi-index
-                 * acpi_index values:
-                 *            0: not present (default value)
-                 *     FFFFFFFF: not supported (old QEMU without PIDX reg)
-                 *        other: device's acpi-index
-                 */
-                ifctx3 = aml_if(aml_lnot(
-                    aml_or(aml_equal(acpi_index, zero),
-                           aml_equal(acpi_index, aml_int(0xFFFFFFFF)), NULL)
-                ));
-                {
-                    byte_list[0] =
-                        1 /* have supported functions */ |
-                        1 << 7 /* support for function 7 */
-                    ;
-                    aml_append(ifctx3, aml_return(aml_buffer(1, byte_list)));
-                }
-                aml_append(ifctx2, ifctx3);
-             }
-             aml_append(ifctx1, ifctx2);
-
-             byte_list[0] = 0; /* nothing supported */
-             aml_append(ifctx1, aml_return(aml_buffer(1, byte_list)));
-         }
-         aml_append(ifctx, ifctx1);
-         elsectx = aml_else();
-         /*
-          * PCI Firmware Specification 3.1
-          * 4.6.7. _DSM for Naming a PCI or PCI Express Device Under
-          *        Operating Systems
-          */
-         ifctx1 = aml_if(aml_equal(func, aml_int(7)));
-         {
-             Aml *pkg = aml_package(2);
-             Aml *ret = aml_local(1);
-
-             aml_append(pkg, zero);
-             /*
-              * optional, if not impl. should return null string
-              */
-             aml_append(pkg, aml_string("%s", ""));
-             aml_append(ifctx1, aml_store(pkg, ret));
-             /*
-              * update acpi-index to actual value
-              */
-             aml_append(ifctx1, aml_store(acpi_index, aml_index(ret, zero)));
-             aml_append(ifctx1, aml_return(ret));
-         }
-         aml_append(elsectx, ifctx1);
-         aml_append(ifctx, elsectx);
+       aml_append(pkg, zero);
+       /*
+        * optional, if not impl. should return null string
+        */
+       aml_append(pkg, aml_string("%s", ""));
+       aml_append(ifctx, aml_store(pkg, ret));
+
+       aml_append(ifctx, aml_store(aml_call2("AIDX", bnum, sunum), acpi_index));
+       /*
+        * update acpi-index to actual value
+        */
+       aml_append(ifctx, aml_store(acpi_index, aml_index(ret, zero)));
     }
+
     aml_append(method, ifctx);
+    aml_append(method, aml_return(ret));
     return method;
 }
 
