linux-kernel - [PATCH 2/2] hvc_xen: fix xenboot for DomUs

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Date:	Wed, 24 Feb 2016 12:23:10 +0000
From:	Stefano Stabellini <stefano.stabellini@...citrix.com>
To:	<xen-devel@...ts.xensource.com>
CC:	<linux-kernel@...r.kernel.org>, <Stefano.Stabellini@...citrix.com>,
	<david.vrabel@...rix.com>, <konrad.wilk@...cle.com>,
	<boris.ostrovsky@...cle.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>
Subject: [PATCH 2/2] hvc_xen: fix xenboot for DomUs

The xenboot early console has been partially broken for DomU for a long
time: the output would only go to the hypervisor via hypercall
(HYPERVISOR_console_io), while it wouldn't actually go to the DomU
console. The reason is that domU_write_console would return early as no
xencons structs are configured for it.

Add an appropriate xencons struct for xenboot from the xenboot setup
callback.

Signed-off-by: Stefano Stabellini <stefano.stabellini@...citrix.com>
---
 drivers/tty/hvc/hvc_xen.c |   32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index 34e8e9f..20fe578 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -246,6 +246,18 @@ err:
 	return -ENODEV;
 }
 
+static int xen_early_pv_console_init(struct xencons_info *info, int vtermno)
+{
+	info->evtchn = xen_start_info->console.domU.evtchn;
+	/* GFN == MFN for PV guest */
+	info->intf = gfn_to_virt(xen_start_info->console.domU.mfn);
+	info->vtermno = vtermno;
+
+	list_add_tail(&info->list, &xenconsoles);
+
+	return 0;
+}
+
 static int xen_pv_console_init(void)
 {
 	struct xencons_info *info;
@@ -265,13 +277,8 @@ static int xen_pv_console_init(void)
 		/* already configured */
 		return 0;
 	}
-	info->evtchn = xen_start_info->console.domU.evtchn;
-	/* GFN == MFN for PV guest */
-	info->intf = gfn_to_virt(xen_start_info->console.domU.mfn);
-	info->vtermno = HVC_COOKIE;
-
 	spin_lock(&xencons_lock);
-	list_add_tail(&info->list, &xenconsoles);
+	xen_early_pv_console_init(info, HVC_COOKIE);
 	spin_unlock(&xencons_lock);
 
 	return 0;
@@ -617,6 +624,18 @@ static void domU_write_early_console(const char *string, unsigned len)
 }
 
 #ifdef CONFIG_EARLY_PRINTK
+static int xenboot_setup_console(struct console *console, char *string)
+{
+	static struct xencons_info xenboot;
+
+	if (xen_initial_domain())
+		return 0;
+	if (!xen_pv_domain())
+		return -ENODEV;
+
+	xen_early_pv_console_init(&xenboot, 0);
+}
+
 static void xenboot_write_console(struct console *console, const char *string,
 				  unsigned len)
 {
@@ -634,6 +653,7 @@ 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,
 	.flags		= CON_PRINTBUFFER | CON_BOOT | CON_ANYTIME,
 	.index		= -1,
 };
-- 
1.7.10.4