Always allow the HPET to be setup, but don't report a frequency back
to the platform time source probe in order to avoid it from being
selected as a valid timer if it's not usable.
Doing the setup even when not intended to be used as a platform timer
is required so that is can be used in legacy replacement mode in order
to assert the IO-APIC is capable of receiving interrupts.
Fixes: c12731493a ('x86/hpet: Use another crystalball to evaluate HPET
usability')
Reported-by: Andrew Cooper <andrew.coop...@citrix.com>
Signed-off-by: Roger Pau Monné <roger....@citrix.com>
---
xen/arch/x86/time.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
index cbadaa036f..a290aba3e8 100644
--- a/xen/arch/x86/time.c
+++ b/xen/arch/x86/time.c
@@ -379,6 +379,12 @@ static int64_t __init init_hpet(struct platform_timesource
*pts)
{
uint64_t hpet_rate, start;
uint32_t count, target;
+ /*
+ * Allow HPET to be setup, but report a frequency of 0 so it's not selected
+ * as a timer source. This is required so it can be used in legacy
+ * replacement mode in check_timer.
+ */
+ bool disable_hpet = false;
if ( hpet_address && strcmp(opt_clocksource, pts->id) &&
cpuidle_using_deep_cstate() )
@@ -391,7 +397,7 @@ static int64_t __init init_hpet(struct platform_timesource
*pts)
case 0x0f1c:
/* HPET on Cherry Trail platforms will halt in deep C states. */
case 0x229c:
- hpet_address = 0;
+ disable_hpet = true;
break;
}
@@ -431,14 +437,14 @@ static int64_t __init init_hpet(struct
platform_timesource *pts)
else if ( !strcmp(opt_clocksource, pts->id) )
printk("HPET use requested via command line, but dysfunctional
in PC10\n");
else
- hpet_address = 0;
+ disable_hpet = true;
}
- if ( !hpet_address )
+ if ( disable_hpet )
printk("Disabling HPET for being unreliable\n");
}
- if ( (hpet_rate = hpet_setup()) == 0 )
+ if ( (hpet_rate = hpet_setup()) == 0 || disable_hpet )
return 0;
pts->frequency = hpet_rate;
--
2.33.0
