Commit 763baca7 authored by Stefano Stabellini's avatar Stefano Stabellini Committed by Juergen Gross
Browse files

xen: introduce xen_console_io option 



Xen can support console_io hypercalls for any domains, not just dom0,
depending on DEBUG and XSM policies. These hypercalls can be very useful
for development and debugging.

Introduce a kernel command line option xen_console_io to enable the
usage of console_io hypercalls for any domain upon request. When
xen_console_io is not specified, the current behavior is retained.

Signed-off-by: default avatarStefano Stabellini <stefano.stabellini@amd.com>
Reviewed-by: default avatarJuergen Gross <jgross@suse.com>
Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
Message-ID: <alpine.DEB.2.22.394.2601131522540.992863@ubuntu-linux-20-04-desktop>
parent dc8ea871

Documentation/admin-guide/kernel-parameters.txt

+5 −0
Original line number Diff line number Diff line
@@ -8414,6 +8414,11 @@ Kernel parameters 
			save/restore/migration must be enabled to handle larger

			domains.



	xen_console_io	[XEN,EARLY]

			Boolean option to enable/disable the usage of the Xen

			console_io hypercalls to read and write to the console.

			Mostly useful for debugging and development.



	xen_emul_unplug=		[HW,X86,XEN,EARLY]

			Unplug Xen emulated devices

			Format: [unplug0,][unplug1]

drivers/tty/hvc/hvc_xen.c

+24 −5
Original line number Diff line number Diff line
@@ -51,6 +51,22 @@ static DEFINE_SPINLOCK(xencons_lock); 


/* ------------------------------------------------------------------ */



static bool xen_console_io = false;

static int __initdata opt_console_io = -1;



static int __init parse_xen_console_io(char *arg)

{

	bool val;

	int ret;



	ret = kstrtobool(arg, &val);

	if (ret == 0)

		opt_console_io = (int)val;



	return ret;

}

early_param("xen_console_io", parse_xen_console_io);



static struct xencons_info *vtermno_to_xencons(int vtermno)

{

	struct xencons_info *entry, *ret = NULL;
@@ -331,7 +347,7 @@ static int xen_initial_domain_console_init(void) 
	struct xencons_info *info;

	unsigned long flags;



	if (!xen_initial_domain())

	if (!xen_console_io)

		return -ENODEV;



	info = vtermno_to_xencons(HVC_COOKIE);
@@ -369,7 +385,7 @@ void xen_console_resume(void) 
{

	struct xencons_info *info = vtermno_to_xencons(HVC_COOKIE);

	if (info != NULL && info->irq) {

		if (!xen_initial_domain())

		if (!xen_console_io)

			xen_console_update_evtchn(info);

		rebind_evtchn_irq(info->evtchn, info->irq);

	}
@@ -601,7 +617,7 @@ static int __init xen_hvc_init(void) 
	if (!xen_domain())

		return -ENODEV;



	if (xen_initial_domain()) {

	if (xen_console_io) {

		ops = &dom0_hvc_ops;

		r = xen_initial_domain_console_init();

		if (r < 0)
@@ -647,14 +663,17 @@ static int __init xen_hvc_init(void) 
}

device_initcall(xen_hvc_init);



static int xen_cons_init(void)

static int __init xen_cons_init(void)

{

	const struct hv_ops *ops;



	xen_console_io = opt_console_io >= 0 ? opt_console_io :

					       xen_initial_domain();



	if (!xen_domain())

		return 0;



	if (xen_initial_domain())

	if (xen_console_io)

		ops = &dom0_hvc_ops;

	else {

		int r;