[RFC PATCH v4 05/21] x86/hpet: Reserve timer for the HPET hardlockup detector

Ricardo Neri
2019-05-24T01:17:08Z

HPET timer 2 will be used to drive the HPET-based hardlockup detector.
Reserve such timer to ensure it cannot be used by user space programs or
for clock events.

When looking for MSI-capable timers for clock events, skip timer 2 if
the HPET hardlockup detector is selected.

Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Andi Kleen <andi.kleen@intel.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Clemens Ladisch <clemens@ladisch.de>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Philippe Ombredanne <pombredanne@nexb.com>
Cc: Kate Stewart <kstewart@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Stephane Eranian <eranian@google.com>
Cc: Suravee Suthikulpanit <Suravee.Suthikulpanit@amd.com>
Cc: "Ravi V. Shankar" <ravi.v.shankar@intel.com>
Cc: x86@kernel.org
Signed-off-by: Ricardo Neri <ricardo.neri-calderon@linux.intel.com>
---
arch/x86/include/asm/hpet.h | 3 +++
arch/x86/kernel/hpet.c | 19 ++++++++++++++++---
2 files changed, 19 insertions(+), 3 deletions(-)

diff --git a/arch/x86/include/asm/hpet.h b/arch/x86/include/asm/hpet.h
index e7098740f5ee..6f099e2781ce 100644
--- a/arch/x86/include/asm/hpet.h
+++ b/arch/x86/include/asm/hpet.h
@@ -61,6 +61,9 @@
*/
#define HPET_MIN_PERIOD 100000UL

+/* Timer used for the hardlockup detector */
+#define HPET_WD_TIMER_NR 2
+
/* hpet memory map physical address */
extern unsigned long hpet_address;
extern unsigned long force_hpet_address;
diff --git a/arch/x86/kernel/hpet.c b/arch/x86/kernel/hpet.c
index 1723d55219e8..ff0250831786 100644
--- a/arch/x86/kernel/hpet.c
+++ b/arch/x86/kernel/hpet.c
@@ -173,7 +173,8 @@ do { \

/*
* When the hpet driver (/dev/hpet) is enabled, we need to reserve
- * timer 0 and timer 1 in case of RTC emulation.
+ * timer 0 and timer 1 in case of RTC emulation. Timer 2 is reserved in case
+ * the HPET-based hardlockup detector is used.
*/
#ifdef CONFIG_HPET

@@ -183,7 +184,7 @@ static void hpet_reserve_platform_timers(unsigned int id)
{
struct hpet __iomem *hpet = hpet_virt_address;
struct hpet_timer __iomem *timer = &hpet->hpet_timers[2];
- unsigned int nrtimers, i;
+ unsigned int nrtimers, i, start_timer;
struct hpet_data hd;

nrtimers = ((id & HPET_ID_NUMBER) >> HPET_ID_NUMBER_SHIFT) + 1;
@@ -198,6 +199,13 @@ static void hpet_reserve_platform_timers(unsigned int id)
hpet_reserve_timer(&hd, 1);
#endif

+ if (IS_ENABLED(CONFIG_X86_HARDLOCKUP_DETECTOR_HPET)) {
+ hpet_reserve_timer(&hd, HPET_WD_TIMER_NR);
+ start_timer = HPET_WD_TIMER_NR + 1;
+ } else {
+ start_timer = HPET_WD_TIMER_NR;
+ }
+
/*
* NOTE that hd_irq[] reflects IOAPIC input pins (LEGACY_8254
* is wrong for i8259!) not the output IRQ. Many BIOS writers
@@ -206,7 +214,7 @@ static void hpet_reserve_platform_timers(unsigned int id)
hd.hd_irq[0] = HPET_LEGACY_8254;
hd.hd_irq[1] = HPET_LEGACY_RTC;

- for (i = 2; i < nrtimers; timer++, i++) {
+ for (i = start_timer; i < nrtimers; timer++, i++) {
hd.hd_irq[i] = (readl(&timer->hpet_config) &
Tn_INT_ROUTE_CNF_MASK) >> Tn_INT_ROUTE_CNF_SHIFT;
}
@@ -651,6 +659,11 @@ static void hpet_msi_capability_lookup(unsigned int start_timer)
struct hpet_dev *hdev = &hpet_devs[num_timers_used];
unsigned int cfg = hpet_readl(HPET_Tn_CFG(i));

+ /* Do not use timer reserved for the HPET watchdog. */
+ if (IS_ENABLED(CONFIG_X86_HARDLOCKUP_DETECTOR_HPET) &&
+ i == HPET_WD_TIMER_NR)
+ continue;
+
/* Only consider HPET timer with MSI support */
if (!(cfg & HPET_TN_FSB_CAP))
continue;
--
2.17.1