[PULL 2/5] acpi: x86: pcihp: add support hotplug on multifunction bridges

["Michael S. Tsirkin" <mst@redhat.com>]

From: Igor Mammedov <imammedo@redhat.com>

Commit [1] switched PCI hotplug from native to ACPI one by default.

That however breaks hotplug on following CLI that used to work:
   -nodefaults -machine q35 \
   -device pcie-root-port,id=pcie-root-port-0,multifunction=on,bus=pcie.0,addr=0x1,chassis=1 \
   -device pcie-root-port,id=pcie-root-port-1,port=0x1,addr=0x1.0x1,bus=pcie.0,chassis=2

where PCI device is hotplugged to pcie-root-port-1 with error on guest side:

  ACPI BIOS Error (bug): Could not resolve symbol [^S0B.PCNT], AE_NOT_FOUND (20201113/psargs-330)
  ACPI Error: Aborting method \_SB.PCI0.PCNT due to previous error (AE_NOT_FOUND) (20201113/psparse-531)
  ACPI Error: Aborting method \_GPE._E01 due to previous error (AE_NOT_FOUND) (20201113/psparse-531)
  ACPI Error: AE_NOT_FOUND, while evaluating GPE method [_E01] (20201113/evgpe-515)

cause is that QEMU's ACPI hotplug never supported functions other then 0
and due to bug it was generating notification entries for not described
functions.

Technically there is no reason not to describe cold-plugged bridges
(root ports) on functions other then 0, as they similarly to bridge
on function 0 are unpluggable.

So since we need to describe multifunction devices iterate over
fuctions as well. But describe only cold-plugged bridges[root ports]
on functions other than 0 as well.

1)
Fixes: 17858a169508609ca9063c544833e5a1adeb7b52 (hw/acpi/ich9: Set ACPI PCI hot-plug as default on Q35)
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reported-by: Laurent Vivier <lvivier@redhat.com>
Message-Id: <20210723090424.2092226-1-imammedo@redhat.com>
Fixes: 17858a169508609ca9063c544833e5a1adeb7b52 (hw/acpi/ich9: Set ACPI PCI hot-plug as default on Q35)<br>
Signed-off-by: Igor Mammedov &lt;<a href="mailto:imammedo@redhat.com" target="_blank">imammedo@redhat.com</a>&gt;<br>
Reported-by: Laurent Vivier &lt;<a href="mailto:lvivier@redhat.com" target="_blank">lvivier@redhat.com</a>&gt;<br>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
---
 hw/i386/acpi-build.c | 44 ++++++++++++++++++++++++++++++--------------
 1 file changed, 30 insertions(+), 14 deletions(-)

diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c
index 17836149fe..a33ac8b91e 100644
--- a/hw/i386/acpi-build.c
+++ b/hw/i386/acpi-build.c
@@ -374,7 +374,7 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
     Aml *dev, *notify_method = NULL, *method;
     QObject *bsel;
     PCIBus *sec;
-    int i;
+    int devfn;
 
     bsel = object_property_get_qobject(OBJECT(bus), ACPI_PCIHP_PROP_BSEL, NULL);
     if (bsel) {
@@ -384,23 +384,31 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
         notify_method = aml_method("DVNT", 2, AML_NOTSERIALIZED);
     }
 
-    for (i = 0; i < ARRAY_SIZE(bus->devices); i += PCI_FUNC_MAX) {
+    for (devfn = 0; devfn < ARRAY_SIZE(bus->devices); devfn++) {
         DeviceClass *dc;
         PCIDeviceClass *pc;
-        PCIDevice *pdev = bus->devices[i];
-        int slot = PCI_SLOT(i);
+        PCIDevice *pdev = bus->devices[devfn];
+        int slot = PCI_SLOT(devfn);
+        int func = PCI_FUNC(devfn);
+        /* ACPI spec: 1.0b: Table 6-2 _ADR Object Bus Types, PCI type */
+        int adr = slot << 16 | func;
         bool hotplug_enabled_dev;
         bool bridge_in_acpi;
         bool cold_plugged_bridge;
 
         if (!pdev) {
-            if (bsel) { /* add hotplug slots for non present devices */
+            /*
+             * add hotplug slots for non present devices.
+             * hotplug is supported only for non-multifunction device
+             * so generate device description only for function 0
+             */
+            if (bsel && !func) {
                 if (pci_bus_is_express(bus) && slot > 0) {
                     break;
                 }
-                dev = aml_device("S%.02X", PCI_DEVFN(slot, 0));
+                dev = aml_device("S%.02X", devfn);
                 aml_append(dev, aml_name_decl("_SUN", aml_int(slot)));
-                aml_append(dev, aml_name_decl("_ADR", aml_int(slot << 16)));
+                aml_append(dev, aml_name_decl("_ADR", aml_int(adr)));
                 method = aml_method("_EJ0", 1, AML_NOTSERIALIZED);
                 aml_append(method,
                     aml_call2("PCEJ", aml_name("BSEL"), aml_name("_SUN"))
@@ -436,9 +444,18 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
             continue;
         }
 
-        /* start to compose PCI slot descriptor */
-        dev = aml_device("S%.02X", PCI_DEVFN(slot, 0));
-        aml_append(dev, aml_name_decl("_ADR", aml_int(slot << 16)));
+        /*
+         * allow describing coldplugged bridges in ACPI even if they are not
+         * on function 0, as they are not unpluggable, for all other devices
+         * generate description only for function 0 per slot
+         */
+        if (func && !bridge_in_acpi) {
+            continue;
+        }
+
+        /* start to compose PCI device descriptor */
+        dev = aml_device("S%.02X", devfn);
+        aml_append(dev, aml_name_decl("_ADR", aml_int(adr)));
 
         if (bsel) {
             /*
@@ -496,7 +513,7 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
 
             build_append_pci_bus_devices(dev, sec_bus, pcihp_bridge_en);
         }
-        /* slot descriptor has been composed, add it into parent context */
+        /* device descriptor has been composed, add it into parent context */
         aml_append(parent_scope, dev);
     }
 
@@ -525,13 +542,12 @@ static void build_append_pci_bus_devices(Aml *parent_scope, PCIBus *bus,
         /* Notify about child bus events in any case */
         if (pcihp_bridge_en) {
             QLIST_FOREACH(sec, &bus->child, sibling) {
-                int32_t devfn = sec->parent_dev->devfn;
-
                 if (pci_bus_is_root(sec)) {
                     continue;
                 }
 
-                aml_append(method, aml_name("^S%.02X.PCNT", devfn));
+                aml_append(method, aml_name("^S%.02X.PCNT",
+                                            sec->parent_dev->devfn));
             }
         }
 
-- 
MST