Support hot insertion and removal of PCI devices on EC2.

Install ACPI notify handlers on PCI devices with an _EJ0 method.  This
handler is invoked when devices are added or removed.

- When an ACPI_NOTIFY_DEVICE_CHECK event posts, rescan the parent bus
  device.  Note that strictly speaking we only need to rescan the
  specified device, but BUS_RESCAN is what is available, so we rescan
  the entire bus.
- When an ACPI_NOTIFY_EJECT_REQUEST event posts, detach the device
  associated with the ACPI handle, invoke the _EJ0 method, and then
  delete the device.

Eventually this might be changed to vector notify events to devd in
userspace where devctl can be used instead to permit more complex
actions such as graceful unmounting of filesystems.

Tested by:	cperciva
Reviewed by:	cperciva, imp, scottl
MFC after:	1 week
Differential Revision:	https://reviews.freebsd.org/D21948

1 files changed, 106 insertions, 0 deletions

diff --git a/sys/dev/acpica/acpi_pci.c b/sys/dev/acpica/acpi_pci.c
index 43a523e326ca..55784625a536 100644
--- a/sys/dev/acpica/acpi_pci.c
+++ b/sys/dev/acpica/acpi_pci.c
@@ -71,9 +71,11 @@ CTASSERT(ACPI_STATE_D2 == PCI_POWERSTATE_D2);
 CTASSERT(ACPI_STATE_D3 == PCI_POWERSTATE_D3);
 
 static struct pci_devinfo *acpi_pci_alloc_devinfo(device_t dev);
+static int	acpi_pci_attach(device_t dev);
 static void	acpi_pci_child_deleted(device_t dev, device_t child);
 static int	acpi_pci_child_location_str_method(device_t cbdev,
 		    device_t child, char *buf, size_t buflen);
+static int	acpi_pci_detach(device_t dev);
 static int	acpi_pci_probe(device_t dev);
 static int	acpi_pci_read_ivar(device_t dev, device_t child, int which,
 		    uintptr_t *result);
@@ -89,6 +91,8 @@ static bus_dma_tag_t acpi_pci_get_dma_tag(device_t bus, device_t child);
 static device_method_t acpi_pci_methods[] = {
 	/* Device interface */
 	DEVMETHOD(device_probe,		acpi_pci_probe),
+	DEVMETHOD(device_attach,	acpi_pci_attach),
+	DEVMETHOD(device_detach,	acpi_pci_detach),
 
 	/* Bus interface */
 	DEVMETHOD(bus_read_ivar,	acpi_pci_read_ivar),
@@ -326,6 +330,108 @@ acpi_pci_probe(device_t dev)
 	return (BUS_PROBE_DEFAULT);
 }
 
+static void
+acpi_pci_device_notify_handler(ACPI_HANDLE h, UINT32 notify, void *context)
+{
+	device_t child, dev;
+	ACPI_STATUS status;
+	int error;
+
+	dev = context;
+
+	switch (notify) {
+	case ACPI_NOTIFY_DEVICE_CHECK:
+		mtx_lock(&Giant);
+		BUS_RESCAN(dev);
+		mtx_unlock(&Giant);
+		break;
+	case ACPI_NOTIFY_EJECT_REQUEST:
+		child = acpi_get_device(h);
+		if (child == NULL) {
+			device_printf(dev, "no device to eject for %s\n",
+			    acpi_name(h));
+			return;
+		}
+		mtx_lock(&Giant);
+		error = device_detach(child);
+		if (error) {
+			mtx_unlock(&Giant);
+			device_printf(dev, "failed to detach %s: %d\n",
+			    device_get_nameunit(child), error);
+			return;
+		}
+		status = acpi_SetInteger(h, "_EJ0", 1);
+		if (ACPI_FAILURE(status)) {
+			mtx_unlock(&Giant);
+			device_printf(dev, "failed to eject %s: %s\n",
+			    acpi_name(h), AcpiFormatException(status));
+			return;
+		}
+		BUS_RESCAN(dev);
+		mtx_unlock(&Giant);
+		break;
+	default:
+		device_printf(dev, "unknown notify %#x for %s\n", notify,
+		    acpi_name(h));
+		break;
+	}
+}
+
+static ACPI_STATUS
+acpi_pci_install_device_notify_handler(ACPI_HANDLE handle, UINT32 level,
+    void *context, void **status)
+{
+	ACPI_HANDLE h;
+
+	ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
+
+	if (ACPI_FAILURE(AcpiGetHandle(handle, "_EJ0", &h)))
+		return_ACPI_STATUS (AE_OK);
+
+	AcpiInstallNotifyHandler(handle, ACPI_SYSTEM_NOTIFY,
+	    acpi_pci_device_notify_handler, context);
+	return_ACPI_STATUS (AE_OK);
+}
+
+static int
+acpi_pci_attach(device_t dev)
+{
+	int error;
+
+	error = pci_attach(dev);
+	if (error)
+		return (error);
+	AcpiWalkNamespace(ACPI_TYPE_DEVICE, acpi_get_handle(dev), 1,
+	    acpi_pci_install_device_notify_handler, NULL, dev, NULL);
+	
+	return (0);
+}
+
+static ACPI_STATUS
+acpi_pci_remove_notify_handler(ACPI_HANDLE handle, UINT32 level, void *context,
+    void **status)
+{
+	ACPI_HANDLE h;
+
+	ACPI_FUNCTION_TRACE((char *)(uintptr_t)__func__);
+
+	if (ACPI_FAILURE(AcpiGetHandle(handle, "_EJ0", &h)))
+		return_ACPI_STATUS (AE_OK);
+
+	AcpiRemoveNotifyHandler(handle, ACPI_SYSTEM_NOTIFY,
+	    acpi_pci_device_notify_handler);
+	return_ACPI_STATUS (AE_OK);
+}
+
+static int
+acpi_pci_detach(device_t dev)
+{
+
+	AcpiWalkNamespace(ACPI_TYPE_DEVICE, acpi_get_handle(dev), 1,
+	    acpi_pci_remove_notify_handler, NULL, dev, NULL);
+	return (pci_detach(dev));
+}
+
 #ifdef ACPI_DMAR
 bus_dma_tag_t dmar_get_dma_tag(device_t dev, device_t child);
 static bus_dma_tag_t