pci: implement power state

This allows to power off pci devices.  In "off" state the devices will
not be visible.  No pci config space access, no pci bar access, no dma.

Default state is "on", so this patch (alone) should not change behavior.

Use case:  Allows hotplug controllers implement slot power.  Hotplug
controllers doing so should set the inital power state for devices in
the ->plug callback.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Message-Id: <20211111130859.1171890-2-kraxel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

2 files changed, 27 insertions, 4 deletions

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index 4a84e47..e5993c1 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -1380,6 +1380,9 @@ static void pci_update_mappings(PCIDevice *d)
             continue;
 
         new_addr = pci_bar_address(d, i, r->type, r->size);
+        if (!d->has_power) {
+            new_addr = PCI_BAR_UNMAPPED;
+        }
 
         /* This bar isn't changed */
         if (new_addr == r->addr)
@@ -1464,8 +1467,8 @@ void pci_default_write_config(PCIDevice *d, uint32_t addr, uint32_t val_in, int
     if (range_covers_byte(addr, l, PCI_COMMAND)) {
         pci_update_irq_disabled(d, was_irq_disabled);
         memory_region_set_enabled(&d->bus_master_enable_region,
-                                  pci_get_word(d->config + PCI_COMMAND)
-                                    & PCI_COMMAND_MASTER);
+                                  (pci_get_word(d->config + PCI_COMMAND)
+                                   & PCI_COMMAND_MASTER) && d->has_power);
     }
 
     msi_write_config(d, addr, val_in, l);
@@ -2182,6 +2185,8 @@ static void pci_qdev_realize(DeviceState *qdev, Error **errp)
         pci_qdev_unrealize(DEVICE(pci_dev));
         return;
     }
+
+    pci_set_power(pci_dev, true);
 }
 
 PCIDevice *pci_new_multifunction(int devfn, bool multifunction,
@@ -2853,6 +2858,22 @@ MSIMessage pci_get_msi_message(PCIDevice *dev, int vector)
     return msg;
 }
 
+void pci_set_power(PCIDevice *d, bool state)
+{
+    if (d->has_power == state) {
+        return;
+    }
+
+    d->has_power = state;
+    pci_update_mappings(d);
+    memory_region_set_enabled(&d->bus_master_enable_region,
+                              (pci_get_word(d->config + PCI_COMMAND)
+                               & PCI_COMMAND_MASTER) && d->has_power);
+    if (!d->has_power) {
+        pci_device_reset(d);
+    }
+}
+
 static const TypeInfo pci_device_type_info = {
     .name = TYPE_PCI_DEVICE,
     .parent = TYPE_DEVICE,
diff --git a/hw/pci/pci_host.c b/hw/pci/pci_host.c
index cf02f0d..7beafd4 100644
--- a/hw/pci/pci_host.c
+++ b/hw/pci/pci_host.c
@@ -74,7 +74,8 @@ void pci_host_config_write_common(PCIDevice *pci_dev, uint32_t addr,
     /* non-zero functions are only exposed when function 0 is present,
      * allowing direct removal of unexposed functions.
      */
-    if (pci_dev->qdev.hotplugged && !pci_get_function_0(pci_dev)) {
+    if ((pci_dev->qdev.hotplugged && !pci_get_function_0(pci_dev)) ||
+        !pci_dev->has_power) {
         return;
     }
 
@@ -97,7 +98,8 @@ uint32_t pci_host_config_read_common(PCIDevice *pci_dev, uint32_t addr,
     /* non-zero functions are only exposed when function 0 is present,
      * allowing direct removal of unexposed functions.
      */
-    if (pci_dev->qdev.hotplugged && !pci_get_function_0(pci_dev)) {
+    if ((pci_dev->qdev.hotplugged && !pci_get_function_0(pci_dev)) ||
+        !pci_dev->has_power) {
         return ~0x0;
     }