[PATCH] kvm: nofity thost when guest is panicked

[Wen Congyang]

Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
---
 drivers/char/virtio_console.c |   49 +++++++++++++++++++++++++++++++++++++++++
 1 files changed, 49 insertions(+), 0 deletions(-)

diff --git a/drivers/char/virtio_console.c b/drivers/char/virtio_console.c
index ddf86b6..ecccd30 100644
--- a/drivers/char/virtio_console.c
+++ b/drivers/char/virtio_console.c
@@ -225,8 +225,14 @@ struct port {
 
 	/* We should allow only one process to open a port */
 	bool guest_connected;
+
+	/* We use this port to tell the host that the guest is panicked */
+	bool panicked_port;
+	char *panicked_buf;
 };
 
+static struct port *panicked_port;
+
 /* This is the very early arch-specified put chars function. */
 static int (*early_put_chars)(u32, const char *, int);
 
@@ -806,6 +812,15 @@ static int port_fops_open(struct inode *inode, struct file *filp)
 		goto out;
 	}
 
+	/*
+	 * Don't allow opening of panicked port devices -- that's reserved
+	 * for kernel space
+	 */
+	if (port->panicked_port) {
+		ret = -ENXIO;
+		goto out;
+	}
+
 	/* Allow only one process to open a particular port at a time */
 	spin_lock_irq(&port->inbuf_lock);
 	if (port->guest_connected) {
@@ -1126,6 +1141,20 @@ static void send_sigio_to_port(struct port *port)
 		kill_fasync(&port->async_queue, SIGIO, POLL_OUT);
 }
 
+static int
+kvm_pv_panic_notify(struct notifier_block *nb, unsigned long code, void *unused)
+{
+	send_control_msg(panicked_port, VIRTIO_CONSOLE_PORT_OPEN, 1);
+	memcpy(panicked_port->panicked_buf, "Kernel panicked\n", 16);
+	send_buf(panicked_port, panicked_port->panicked_buf, 16, true);
+	send_control_msg(panicked_port, VIRTIO_CONSOLE_CONSOLE_PORT, 0);
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block kvm_pv_panic_nb = {
+	.notifier_call = kvm_pv_panic_notify,
+};
+
 static int add_port(struct ports_device *portdev, u32 id)
 {
 	char debugfs_name[16];
@@ -1262,6 +1291,10 @@ static void remove_port(struct kref *kref)
 
 	debugfs_remove(port->debugfs_file);
 
+	if (port->panicked_port)
+		atomic_notifier_chain_unregister(&panic_notifier_list,
+						 &kvm_pv_panic_nb);
+
 	kfree(port);
 }
 
@@ -1433,6 +1466,22 @@ static void handle_control_message(struct ports_device *portdev,
 			name_size - 1);
 		port->name[name_size - 1] = 0;
 
+		if (!panicked_port && !strcmp(port->name, "status")) {
+			port->panicked_buf = kmalloc(PAGE_SIZE, GFP_KERNEL);
+			if (!port->panicked_buf) {
+				dev_warn(port->dev,
+					 "Not enough space to store panicked"
+					 " message");
+				goto skip;
+			}
+			send_sigio_to_port(port);
+			port->panicked_port = true;
+			panicked_port = port;
+			atomic_notifier_chain_register(&panic_notifier_list,
+						       &kvm_pv_panic_nb);
+		}
+
+skip:
 		/*
 		 * Since we only have one sysfs attribute, 'name',
 		 * create it only if we have a name for the port.
-- 
1.7.1


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