1 files changed, 136 insertions, 58 deletions

diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index 5ef08905fe05..388a71afd6ef 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -37,10 +37,13 @@ struct xencons_info {
 	struct xenbus_device *xbdev;
 	struct xencons_interface *intf;
 	unsigned int evtchn;
+	XENCONS_RING_IDX out_cons;
+	unsigned int out_cons_same;
 	struct hvc_struct *hvc;
 	int irq;
 	int vtermno;
 	grant_ref_t gntref;
+	spinlock_t ring_lock;
 };
 
 static LIST_HEAD(xenconsoles);
@@ -50,17 +53,22 @@ static DEFINE_SPINLOCK(xencons_lock);
 
 static struct xencons_info *vtermno_to_xencons(int vtermno)
 {
-	struct xencons_info *entry, *n, *ret = NULL;
+	struct xencons_info *entry, *ret = NULL;
+	unsigned long flags;
 
-	if (list_empty(&xenconsoles))
-			return NULL;
+	spin_lock_irqsave(&xencons_lock, flags);
+	if (list_empty(&xenconsoles)) {
+		spin_unlock_irqrestore(&xencons_lock, flags);
+		return NULL;
+	}
 
-	list_for_each_entry_safe(entry, n, &xenconsoles, list) {
+	list_for_each_entry(entry, &xenconsoles, list) {
 		if (entry->vtermno == vtermno) {
 			ret  = entry;
 			break;
 		}
 	}
+	spin_unlock_irqrestore(&xencons_lock, flags);
 
 	return ret;
 }
@@ -76,33 +84,42 @@ static inline void notify_daemon(struct xencons_info *cons)
 	notify_remote_via_evtchn(cons->evtchn);
 }
 
-static int __write_console(struct xencons_info *xencons,
-		const char *data, int len)
+static ssize_t __write_console(struct xencons_info *xencons,
+			       const u8 *data, size_t len)
 {
 	XENCONS_RING_IDX cons, prod;
 	struct xencons_interface *intf = xencons->intf;
-	int sent = 0;
+	unsigned long flags;
+	size_t sent = 0;
 
+	spin_lock_irqsave(&xencons->ring_lock, flags);
 	cons = intf->out_cons;
 	prod = intf->out_prod;
 	mb();			/* update queue values before going on */
-	BUG_ON((prod - cons) > sizeof(intf->out));
+
+	if ((prod - cons) > sizeof(intf->out)) {
+		spin_unlock_irqrestore(&xencons->ring_lock, flags);
+		pr_err_once("xencons: Illegal ring page indices");
+		return -EINVAL;
+	}
 
 	while ((sent < len) && ((prod - cons) < sizeof(intf->out)))
 		intf->out[MASK_XENCONS_IDX(prod++, intf->out)] = data[sent++];
 
 	wmb();			/* write ring before updating pointer */
 	intf->out_prod = prod;
+	spin_unlock_irqrestore(&xencons->ring_lock, flags);
 
 	if (sent)
 		notify_daemon(xencons);
 	return sent;
 }
 
-static int domU_write_console(uint32_t vtermno, const char *data, int len)
+static ssize_t domU_write_console(uint32_t vtermno, const u8 *data, size_t len)
 {
-	int ret = len;
 	struct xencons_info *cons = vtermno_to_xencons(vtermno);
+	size_t ret = len;
+
 	if (cons == NULL)
 		return -EINVAL;
 
@@ -113,8 +130,11 @@ static int domU_write_console(uint32_t vtermno, const char *data, int len)
 	 * kernel is crippled.
 	 */
 	while (len) {
-		int sent = __write_console(cons, data, len);
-		
+		ssize_t sent = __write_console(cons, data, len);
+
+		if (sent < 0)
+			return sent;
+
 		data += sent;
 		len -= sent;
 
@@ -125,20 +145,29 @@ static int domU_write_console(uint32_t vtermno, const char *data, int len)
 	return ret;
 }
 
-static int domU_read_console(uint32_t vtermno, char *buf, int len)
+static ssize_t domU_read_console(uint32_t vtermno, u8 *buf, size_t len)
 {
 	struct xencons_interface *intf;
 	XENCONS_RING_IDX cons, prod;
-	int recv = 0;
 	struct xencons_info *xencons = vtermno_to_xencons(vtermno);
+	unsigned int eoiflag = 0;
+	unsigned long flags;
+	size_t recv = 0;
+
 	if (xencons == NULL)
 		return -EINVAL;
 	intf = xencons->intf;
 
+	spin_lock_irqsave(&xencons->ring_lock, flags);
 	cons = intf->in_cons;
 	prod = intf->in_prod;
 	mb();			/* get pointers before reading ring */
-	BUG_ON((prod - cons) > sizeof(intf->in));
+
+	if ((prod - cons) > sizeof(intf->in)) {
+		spin_unlock_irqrestore(&xencons->ring_lock, flags);
+		pr_err_once("xencons: Illegal ring page indices");
+		return -EINVAL;
+	}
 
 	while (cons != prod && recv < len)
 		buf[recv++] = intf->in[MASK_XENCONS_IDX(cons++, intf->in)];
@@ -146,7 +175,30 @@ static int domU_read_console(uint32_t vtermno, char *buf, int len)
 	mb();			/* read ring before consuming */
 	intf->in_cons = cons;
 
-	notify_daemon(xencons);
+	/*
+	 * When to mark interrupt having been spurious:
+	 * - there was no new data to be read, and
+	 * - the backend did not consume some output bytes, and
+	 * - the previous round with no read data didn't see consumed bytes
+	 *   (we might have a race with an interrupt being in flight while
+	 *   updating xencons->out_cons, so account for that by allowing one
+	 *   round without any visible reason)
+	 */
+	if (intf->out_cons != xencons->out_cons) {
+		xencons->out_cons = intf->out_cons;
+		xencons->out_cons_same = 0;
+	}
+	if (!recv && xencons->out_cons_same++ > 1) {
+		eoiflag = XEN_EOI_FLAG_SPURIOUS;
+	}
+	spin_unlock_irqrestore(&xencons->ring_lock, flags);
+
+	if (recv) {
+		notify_daemon(xencons);
+	}
+
+	xen_irq_lateeoi(xencons->irq, eoiflag);
+
 	return recv;
 }
 
@@ -158,7 +210,7 @@ static const struct hv_ops domU_hvc_ops = {
 	.notifier_hangup = notifier_hangup_irq,
 };
 
-static int dom0_read_console(uint32_t vtermno, char *buf, int len)
+static ssize_t dom0_read_console(uint32_t vtermno, u8 *buf, size_t len)
 {
 	return HYPERVISOR_console_io(CONSOLEIO_read, len, buf);
 }
@@ -167,9 +219,9 @@ static int dom0_read_console(uint32_t vtermno, char *buf, int len)
  * Either for a dom0 to write to the system console, or a domU with a
  * debug version of Xen
  */
-static int dom0_write_console(uint32_t vtermno, const char *str, int len)
+static ssize_t dom0_write_console(uint32_t vtermno, const u8 *str, size_t len)
 {
-	int rc = HYPERVISOR_console_io(CONSOLEIO_write, len, (char *)str);
+	int rc = HYPERVISOR_console_io(CONSOLEIO_write, len, (u8 *)str);
 	if (rc < 0)
 		return rc;
 
@@ -188,7 +240,7 @@ static int xen_hvm_console_init(void)
 {
 	int r;
 	uint64_t v = 0;
-	unsigned long gfn;
+	unsigned long gfn, flags;
 	struct xencons_info *info;
 
 	if (!xen_hvm_domain())
@@ -199,6 +251,7 @@ static int xen_hvm_console_init(void)
 		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
 		if (!info)
 			return -ENOMEM;
+		spin_lock_init(&info->ring_lock);
 	} else if (info->intf != NULL) {
 		/* already configured */
 		return 0;
@@ -218,14 +271,14 @@ static int xen_hvm_console_init(void)
 	if (r < 0 || v == 0)
 		goto err;
 	gfn = v;
-	info->intf = xen_remap(gfn << XEN_PAGE_SHIFT, XEN_PAGE_SIZE);
+	info->intf = memremap(gfn << XEN_PAGE_SHIFT, XEN_PAGE_SIZE, MEMREMAP_WB);
 	if (info->intf == NULL)
 		goto err;
 	info->vtermno = HVC_COOKIE;
 
-	spin_lock(&xencons_lock);
+	spin_lock_irqsave(&xencons_lock, flags);
 	list_add_tail(&info->list, &xenconsoles);
-	spin_unlock(&xencons_lock);
+	spin_unlock_irqrestore(&xencons_lock, flags);
 
 	return 0;
 err:
@@ -235,6 +288,7 @@ err:
 
 static int xencons_info_pv_init(struct xencons_info *info, int vtermno)
 {
+	spin_lock_init(&info->ring_lock);
 	info->evtchn = xen_start_info->console.domU.evtchn;
 	/* GFN == MFN for PV guest */
 	info->intf = gfn_to_virt(xen_start_info->console.domU.mfn);
@@ -248,6 +302,7 @@ static int xencons_info_pv_init(struct xencons_info *info, int vtermno)
 static int xen_pv_console_init(void)
 {
 	struct xencons_info *info;
+	unsigned long flags;
 
 	if (!xen_pv_domain())
 		return -ENODEV;
@@ -264,9 +319,9 @@ static int xen_pv_console_init(void)
 		/* already configured */
 		return 0;
 	}
-	spin_lock(&xencons_lock);
+	spin_lock_irqsave(&xencons_lock, flags);
 	xencons_info_pv_init(info, HVC_COOKIE);
-	spin_unlock(&xencons_lock);
+	spin_unlock_irqrestore(&xencons_lock, flags);
 
 	return 0;
 }
@@ -274,6 +329,7 @@ static int xen_pv_console_init(void)
 static int xen_initial_domain_console_init(void)
 {
 	struct xencons_info *info;
+	unsigned long flags;
 
 	if (!xen_initial_domain())
 		return -ENODEV;
@@ -283,14 +339,15 @@ static int xen_initial_domain_console_init(void)
 		info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
 		if (!info)
 			return -ENOMEM;
+		spin_lock_init(&info->ring_lock);
 	}
 
 	info->irq = bind_virq_to_irq(VIRQ_CONSOLE, 0, false);
 	info->vtermno = HVC_COOKIE;
 
-	spin_lock(&xencons_lock);
+	spin_lock_irqsave(&xencons_lock, flags);
 	list_add_tail(&info->list, &xenconsoles);
-	spin_unlock(&xencons_lock);
+	spin_unlock_irqrestore(&xencons_lock, flags);
 
 	return 0;
 }
@@ -321,18 +378,21 @@ void xen_console_resume(void)
 #ifdef CONFIG_HVC_XEN_FRONTEND
 static void xencons_disconnect_backend(struct xencons_info *info)
 {
-	if (info->irq > 0)
-		unbind_from_irqhandler(info->irq, NULL);
-	info->irq = 0;
+	if (info->hvc != NULL)
+		hvc_remove(info->hvc);
+	info->hvc = NULL;
+	if (info->irq > 0) {
+		evtchn_put(info->evtchn);
+		info->irq = 0;
+		info->evtchn = 0;
+	}
+	/* evtchn_put() will also close it so this is only an error path */
 	if (info->evtchn > 0)
 		xenbus_free_evtchn(info->xbdev, info->evtchn);
 	info->evtchn = 0;
 	if (info->gntref > 0)
 		gnttab_free_grant_references(info->gntref);
 	info->gntref = 0;
-	if (info->hvc != NULL)
-		hvc_remove(info->hvc);
-	info->hvc = NULL;
 }
 
 static void xencons_free(struct xencons_info *info)
@@ -345,10 +405,12 @@ static void xencons_free(struct xencons_info *info)
 
 static int xen_console_remove(struct xencons_info *info)
 {
+	unsigned long flags;
+
 	xencons_disconnect_backend(info);
-	spin_lock(&xencons_lock);
+	spin_lock_irqsave(&xencons_lock, flags);
 	list_del(&info->list);
-	spin_unlock(&xencons_lock);
+	spin_unlock_irqrestore(&xencons_lock, flags);
 	if (info->xbdev != NULL)
 		xencons_free(info);
 	else {
@@ -359,9 +421,9 @@ static int xen_console_remove(struct xencons_info *info)
 	return 0;
 }
 
-static int xencons_remove(struct xenbus_device *dev)
+static void xencons_remove(struct xenbus_device *dev)
 {
-	return xen_console_remove(dev_get_drvdata(&dev->dev));
+	xen_console_remove(dev_get_drvdata(&dev->dev));
 }
 
 static int xencons_connect_backend(struct xenbus_device *dev,
@@ -375,7 +437,7 @@ static int xencons_connect_backend(struct xenbus_device *dev,
 	if (ret)
 		return ret;
 	info->evtchn = evtchn;
-	irq = bind_evtchn_to_irq(evtchn);
+	irq = bind_evtchn_to_irq_lateeoi(evtchn);
 	if (irq < 0)
 		return irq;
 	info->irq = irq;
@@ -429,6 +491,7 @@ static int xencons_probe(struct xenbus_device *dev,
 {
 	int ret, devid;
 	struct xencons_info *info;
+	unsigned long flags;
 
 	devid = dev->nodename[strlen(dev->nodename) - 1] - '0';
 	if (devid == 0)
@@ -437,6 +500,7 @@ static int xencons_probe(struct xenbus_device *dev,
 	info = kzalloc(sizeof(struct xencons_info), GFP_KERNEL);
 	if (!info)
 		return -ENOMEM;
+	spin_lock_init(&info->ring_lock);
 	dev_set_drvdata(&dev->dev, info);
 	info->xbdev = dev;
 	info->vtermno = xenbus_devid_to_vtermno(devid);
@@ -447,9 +511,9 @@ static int xencons_probe(struct xenbus_device *dev,
 	ret = xencons_connect_backend(dev, info);
 	if (ret < 0)
 		goto error;
-	spin_lock(&xencons_lock);
+	spin_lock_irqsave(&xencons_lock, flags);
 	list_add_tail(&info->list, &xenconsoles);
-	spin_unlock(&xencons_lock);
+	spin_unlock_irqrestore(&xencons_lock, flags);
 
 	return 0;
 
@@ -492,11 +556,24 @@ static void xencons_backend_changed(struct xenbus_device *dev,
 	case XenbusStateClosed:
 		if (dev->state == XenbusStateClosed)
 			break;
-		/* fall through - Missed the backend's CLOSING state. */
-	case XenbusStateClosing:
+		fallthrough;	/* Missed the backend's CLOSING state */
+	case XenbusStateClosing: {
+		struct xencons_info *info = dev_get_drvdata(&dev->dev);
+
+		/*
+		 * Don't tear down the evtchn and grant ref before the other
+		 * end has disconnected, but do stop userspace from trying
+		 * to use the device before we allow the backend to close.
+		 */
+		if (info->hvc) {
+			hvc_remove(info->hvc);
+			info->hvc = NULL;
+		}
+
 		xenbus_frontend_closed(dev);
 		break;
 	}
+	}
 }
 
 static const struct xenbus_device_id xencons_ids[] = {
@@ -511,6 +588,7 @@ static struct xenbus_driver xencons_driver = {
 	.remove = xencons_remove,
 	.resume = xencons_resume,
 	.otherend_changed = xencons_backend_changed,
+	.not_essential = true,
 };
 #endif /* CONFIG_HVC_XEN_FRONTEND */
 
@@ -527,7 +605,7 @@ static int __init xen_hvc_init(void)
 		ops = &dom0_hvc_ops;
 		r = xen_initial_domain_console_init();
 		if (r < 0)
-			return r;
+			goto register_fe;
 		info = vtermno_to_xencons(HVC_COOKIE);
 	} else {
 		ops = &domU_hvc_ops;
@@ -536,10 +614,10 @@ static int __init xen_hvc_init(void)
 		else
 			r = xen_pv_console_init();
 		if (r < 0)
-			return r;
+			goto register_fe;
 
 		info = vtermno_to_xencons(HVC_COOKIE);
-		info->irq = bind_evtchn_to_irq(info->evtchn);
+		info->irq = bind_evtchn_to_irq_lateeoi(info->evtchn);
 	}
 	if (info->irq < 0)
 		info->irq = 0; /* NO_IRQ */
@@ -548,17 +626,20 @@ static int __init xen_hvc_init(void)
 
 	info->hvc = hvc_alloc(HVC_COOKIE, info->irq, ops, 256);
 	if (IS_ERR(info->hvc)) {
+		unsigned long flags;
+
 		r = PTR_ERR(info->hvc);
-		spin_lock(&xencons_lock);
+		spin_lock_irqsave(&xencons_lock, flags);
 		list_del(&info->list);
-		spin_unlock(&xencons_lock);
+		spin_unlock_irqrestore(&xencons_lock, flags);
 		if (info->irq)
-			unbind_from_irqhandler(info->irq, NULL);
+			evtchn_put(info->evtchn);
 		kfree(info);
 		return r;
 	}
 
 	r = 0;
+ register_fe:
 #ifdef CONFIG_HVC_XEN_FRONTEND
 	r = xenbus_register_frontend(&xencons_driver);
 #endif
@@ -603,14 +684,12 @@ static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len) { }
 #endif
 
 #ifdef CONFIG_EARLY_PRINTK
-static int __init xenboot_setup_console(struct console *console, char *string)
+static int __init xenboot_console_setup(struct console *console, char *string)
 {
 	static struct xencons_info xenboot;
 
-	if (xen_initial_domain())
+	if (xen_initial_domain() || !xen_pv_domain())
 		return 0;
-	if (!xen_pv_domain())
-		return -ENODEV;
 
 	return xencons_info_pv_init(&xenboot, 0);
 }
@@ -621,17 +700,16 @@ static void xenboot_write_console(struct console *console, const char *string,
 	unsigned int linelen, off = 0;
 	const char *pos;
 
+	if (dom0_write_console(0, string, len) >= 0)
+		return;
+
 	if (!xen_pv_domain()) {
 		xen_hvm_early_write(0, string, len);
 		return;
 	}
 
-	dom0_write_console(0, string, len);
-
-	if (xen_initial_domain())
+	if (domU_write_console(0, "(early) ", 8) < 0)
 		return;
-
-	domU_write_console(0, "(early) ", 8);
 	while (off < len && NULL != (pos = strchr(string+off, '\n'))) {
 		linelen = pos-string+off;
 		if (off + linelen > len)
@@ -647,7 +725,7 @@ static void xenboot_write_console(struct console *console, const char *string,
 struct console xenboot_console = {
 	.name		= "xenboot",
 	.write		= xenboot_write_console,
-	.setup		= xenboot_setup_console,
+	.setup		= xenboot_console_setup,
 	.flags		= CON_PRINTBUFFER | CON_BOOT | CON_ANYTIME,
 	.index		= -1,
 };