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xen: introduce xen_console_io option

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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: Stefano Stabellini <stefano.stabellini@amd.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Message-ID: <alpine.DEB.2.22.394.2601131522540.992863@ubuntu-linux-20-04-desktop>
This commit is contained in:
Stefano Stabellini 2026-01-13 15:24:20 -08:00 • committed by Juergen Gross
parent dc8ea87143
commit 763baca7bf
2 changed files with 29 additions and 5 deletions
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5
Documentation/admin-guide/kernel-parameters.txt
View file

@ -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]

29
drivers/tty/hvc/hvc_xen.c
View file

@ -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;