[PATCH v2 10/10] clocksource/drivers/hyper-v: Move handling of STIMER0 interrupts
From: Michael Kelley
Date: Sun Feb 28 2021 - 20:20:17 EST
STIMER0 interrupts are most naturally modeled as per-cpu IRQs. But
because x86/x64 doesn't have per-cpu IRQs, the core STIMER0 interrupt
handling machinery is done in code under arch/x86 and Linux IRQs are
not used. Adding support for ARM64 means adding equivalent code
using per-cpu IRQs under arch/arm64.
A better model is to treat per-cpu IRQs as the normal path (which it is
for modern architectures), and the x86/x64 path as the exception. Do this
by incorporating standard Linux per-cpu IRQ allocation into the main
SITMER0 driver code, and bypass it in the x86/x64 exception case. For
x86/x64, special case code is retained under arch/x86, but no STIMER0
interrupt handling code is needed under arch/arm64.
No functional change.
Signed-off-by: Michael Kelley <mikelley@xxxxxxxxxxxxx>
---
arch/x86/hyperv/hv_init.c | 2 +-
arch/x86/include/asm/mshyperv.h | 4 -
arch/x86/kernel/cpu/mshyperv.c | 10 +--
drivers/clocksource/hyperv_timer.c | 180 ++++++++++++++++++++++++++-----------
include/asm-generic/mshyperv.h | 5 --
include/clocksource/hyperv_timer.h | 3 +-
6 files changed, 132 insertions(+), 72 deletions(-)
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 9af4f8a..9d10025 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -327,7 +327,7 @@ static void __init hv_stimer_setup_percpu_clockev(void)
* Ignore any errors in setting up stimer clockevents
* as we can run with the LAPIC timer as a fallback.
*/
- (void)hv_stimer_alloc();
+ (void)hv_stimer_alloc(false);
/*
* Still register the LAPIC timer, because the direct-mode STIMER is
diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h
index 5433312..6d4891b 100644
--- a/arch/x86/include/asm/mshyperv.h
+++ b/arch/x86/include/asm/mshyperv.h
@@ -31,10 +31,6 @@ static inline u64 hv_get_register(unsigned int reg)
void hyperv_vector_handler(struct pt_regs *regs);
-static inline void hv_enable_stimer0_percpu_irq(int irq) {}
-static inline void hv_disable_stimer0_percpu_irq(int irq) {}
-
-
#if IS_ENABLED(CONFIG_HYPERV)
extern int hyperv_init_cpuhp;
diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
index 41fd84a..cebed53 100644
--- a/arch/x86/kernel/cpu/mshyperv.c
+++ b/arch/x86/kernel/cpu/mshyperv.c
@@ -90,21 +90,17 @@ void hv_remove_vmbus_handler(void)
set_irq_regs(old_regs);
}
-int hv_setup_stimer0_irq(int *irq, int *vector, void (*handler)(void))
+/* For x86/x64, override weak placeholders in hyperv_timer.c */
+void hv_setup_stimer0_handler(void (*handler)(void))
{
- *vector = HYPERV_STIMER0_VECTOR;
- *irq = -1; /* Unused on x86/x64 */
hv_stimer0_handler = handler;
- return 0;
}
-EXPORT_SYMBOL_GPL(hv_setup_stimer0_irq);
-void hv_remove_stimer0_irq(int irq)
+void hv_remove_stimer0_handler(void)
{
/* We have no way to deallocate the interrupt gate */
hv_stimer0_handler = NULL;
}
-EXPORT_SYMBOL_GPL(hv_remove_stimer0_irq);
void hv_setup_kexec_handler(void (*handler)(void))
{
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index cdb8e0c..b2bf5e5 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -18,6 +18,9 @@
#include <linux/sched_clock.h>
#include <linux/mm.h>
#include <linux/cpuhotplug.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/acpi.h>
#include <clocksource/hyperv_timer.h>
#include <asm/hyperv-tlfs.h>
#include <asm/mshyperv.h>
@@ -43,14 +46,13 @@
*/
static bool direct_mode_enabled;
-static int stimer0_irq;
-static int stimer0_vector;
+static int stimer0_irq = -1;
+static long __percpu *stimer0_evt;
static int stimer0_message_sint;
/*
- * ISR for when stimer0 is operating in Direct Mode. Direct Mode
- * does not use VMbus or any VMbus messages, so process here and not
- * in the VMbus driver code.
+ * Common code for stimer0 interrupts coming via Direct Mode or
+ * as a VMbus message.
*/
void hv_stimer0_isr(void)
{
@@ -61,6 +63,16 @@ void hv_stimer0_isr(void)
}
EXPORT_SYMBOL_GPL(hv_stimer0_isr);
+/*
+ * stimer0 interrupt handler for architectures that support
+ * per-cpu interrupts, which also implies Direct Mode.
+ */
+static irqreturn_t hv_stimer0_percpu_isr(int irq, void *dev_id)
+{
+ hv_stimer0_isr();
+ return IRQ_HANDLED;
+}
+
static int hv_ce_set_next_event(unsigned long delta,
struct clock_event_device *evt)
{
@@ -76,8 +88,8 @@ static int hv_ce_shutdown(struct clock_event_device *evt)
{
hv_set_register(HV_REGISTER_STIMER0_COUNT, 0);
hv_set_register(HV_REGISTER_STIMER0_CONFIG, 0);
- if (direct_mode_enabled)
- hv_disable_stimer0_percpu_irq(stimer0_irq);
+ if (direct_mode_enabled && stimer0_irq >= 0)
+ disable_percpu_irq(stimer0_irq);
return 0;
}
@@ -95,8 +107,9 @@ static int hv_ce_set_oneshot(struct clock_event_device *evt)
* on the specified hardware vector/IRQ.
*/
timer_cfg.direct_mode = 1;
- timer_cfg.apic_vector = stimer0_vector;
- hv_enable_stimer0_percpu_irq(stimer0_irq);
+ timer_cfg.apic_vector = HYPERV_STIMER0_VECTOR;
+ if (stimer0_irq >= 0)
+ enable_percpu_irq(stimer0_irq, IRQ_TYPE_NONE);
} else {
/*
* When it expires, the timer will generate a VMbus message,
@@ -169,10 +182,70 @@ int hv_stimer_cleanup(unsigned int cpu)
}
EXPORT_SYMBOL_GPL(hv_stimer_cleanup);
+/*
+ * These placeholders are overridden by arch specific code on
+ * architectures that need special setup of the stimer0 IRQ because
+ * they don't support per-cpu IRQs (such as x86/x64).
+ */
+void __weak hv_setup_stimer0_handler(void (*handler)(void))
+{
+};
+
+void __weak hv_remove_stimer0_handler(void)
+{
+};
+
+/* Called only on architectures with per-cpu IRQs (i.e., not x86/x64) */
+static int hv_setup_stimer0_irq(void)
+{
+ int ret;
+
+ ret = acpi_register_gsi(NULL, HYPERV_STIMER0_VECTOR,
+ ACPI_EDGE_SENSITIVE, ACPI_ACTIVE_HIGH);
+ if (ret < 0) {
+ pr_err("Can't register Hyper-V stimer0 GSI. Error %d", ret);
+ return ret;
+ }
+ stimer0_irq = ret;
+
+ stimer0_evt = alloc_percpu(long);
+ if (!stimer0_evt) {
+ ret = -ENOMEM;
+ goto unregister_gsi;
+ }
+ ret = request_percpu_irq(stimer0_irq, hv_stimer0_percpu_isr,
+ "Hyper-V stimer0", stimer0_evt);
+ if (ret) {
+ pr_err("Can't request Hyper-V stimer0 IRQ %d. Error %d",
+ stimer0_irq, ret);
+ goto free_stimer0_evt;
+ }
+ return ret;
+
+free_stimer0_evt:
+ free_percpu(stimer0_evt);
+unregister_gsi:
+ acpi_unregister_gsi(stimer0_irq);
+ stimer0_irq = -1;
+ return ret;
+}
+
+static void hv_remove_stimer0_irq(void)
+{
+ if (stimer0_irq == -1) {
+ hv_remove_stimer0_handler();
+ } else {
+ free_percpu_irq(stimer0_irq, stimer0_evt);
+ free_percpu(stimer0_evt);
+ acpi_unregister_gsi(stimer0_irq);
+ stimer0_irq = -1;
+ }
+}
+
/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
-int hv_stimer_alloc(void)
+int hv_stimer_alloc(bool have_percpu_irqs)
{
- int ret = 0;
+ int ret;
/*
* Synthetic timers are always available except on old versions of
@@ -188,29 +261,37 @@ int hv_stimer_alloc(void)
direct_mode_enabled = ms_hyperv.misc_features &
HV_STIMER_DIRECT_MODE_AVAILABLE;
- if (direct_mode_enabled) {
- ret = hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
- hv_stimer0_isr);
+
+ /*
+ * If Direct Mode isn't enabled, the remainder of the initialization
+ * is done later by hv_stimer_legacy_init()
+ */
+ if (!direct_mode_enabled)
+ return 0;
+
+ if (have_percpu_irqs) {
+ ret = hv_setup_stimer0_irq();
if (ret)
- goto free_percpu;
+ goto free_clock_event;
+ } else {
+ hv_setup_stimer0_handler(hv_stimer0_isr);
+ }
- /*
- * Since we are in Direct Mode, stimer initialization
- * can be done now with a CPUHP value in the same range
- * as other clockevent devices.
- */
- ret = cpuhp_setup_state(CPUHP_AP_HYPERV_TIMER_STARTING,
- "clockevents/hyperv/stimer:starting",
- hv_stimer_init, hv_stimer_cleanup);
- if (ret < 0)
- goto free_stimer0_irq;
+ /*
+ * Since we are in Direct Mode, stimer initialization
+ * can be done now with a CPUHP value in the same range
+ * as other clockevent devices.
+ */
+ ret = cpuhp_setup_state(CPUHP_AP_HYPERV_TIMER_STARTING,
+ "clockevents/hyperv/stimer:starting",
+ hv_stimer_init, hv_stimer_cleanup);
+ if (ret < 0) {
+ hv_remove_stimer0_irq();
+ goto free_clock_event;
}
return ret;
-free_stimer0_irq:
- hv_remove_stimer0_irq(stimer0_irq);
- stimer0_irq = 0;
-free_percpu:
+free_clock_event:
free_percpu(hv_clock_event);
hv_clock_event = NULL;
return ret;
@@ -254,23 +335,6 @@ void hv_stimer_legacy_cleanup(unsigned int cpu)
}
EXPORT_SYMBOL_GPL(hv_stimer_legacy_cleanup);
-
-/* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
-void hv_stimer_free(void)
-{
- if (!hv_clock_event)
- return;
-
- if (direct_mode_enabled) {
- cpuhp_remove_state(CPUHP_AP_HYPERV_TIMER_STARTING);
- hv_remove_stimer0_irq(stimer0_irq);
- stimer0_irq = 0;
- }
- free_percpu(hv_clock_event);
- hv_clock_event = NULL;
-}
-EXPORT_SYMBOL_GPL(hv_stimer_free);
-
/*
* Do a global cleanup of clockevents for the cases of kexec and
* vmbus exit
@@ -287,12 +351,17 @@ void hv_stimer_global_cleanup(void)
hv_stimer_legacy_cleanup(cpu);
}
- /*
- * If Direct Mode is enabled, the cpuhp teardown callback
- * (hv_stimer_cleanup) will be run on all CPUs to stop the
- * stimers.
- */
- hv_stimer_free();
+ if (!hv_clock_event)
+ return;
+
+ if (direct_mode_enabled) {
+ cpuhp_remove_state(CPUHP_AP_HYPERV_TIMER_STARTING);
+ hv_remove_stimer0_irq();
+ stimer0_irq = -1;
+ }
+ free_percpu(hv_clock_event);
+ hv_clock_event = NULL;
+
}
EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
@@ -454,9 +523,14 @@ static bool __init hv_init_tsc_clocksource(void)
* Hyper-V Reference TSC rating, causing the generic TSC to be used.
* TSC_INVARIANT is not offered on ARM64, so the Hyper-V Reference
* TSC will be preferred over the virtualized ARM64 arch counter.
+ * While the Hyper-V MSR clocksource won't be used since the
+ * Reference TSC clocksource is present, change its rating as
+ * well for consistency.
*/
- if (ms_hyperv.features & HV_ACCESS_TSC_INVARIANT)
+ if (ms_hyperv.features & HV_ACCESS_TSC_INVARIANT) {
hyperv_cs_tsc.rating = 250;
+ hyperv_cs_msr.rating = 250;
+ }
hv_read_reference_counter = read_hv_clock_tsc;
phys_addr = virt_to_phys(hv_get_tsc_page());
diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h
index 43dc371..69e7fe0 100644
--- a/include/asm-generic/mshyperv.h
+++ b/include/asm-generic/mshyperv.h
@@ -183,9 +183,4 @@ static inline int cpumask_to_vpset(struct hv_vpset *vpset,
static inline void hyperv_cleanup(void) {}
#endif /* CONFIG_HYPERV */
-#if IS_ENABLED(CONFIG_HYPERV)
-extern int hv_setup_stimer0_irq(int *irq, int *vector, void (*handler)(void));
-extern void hv_remove_stimer0_irq(int irq);
-#endif
-
#endif
diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h
index 34eef083..b6774aa 100644
--- a/include/clocksource/hyperv_timer.h
+++ b/include/clocksource/hyperv_timer.h
@@ -21,8 +21,7 @@
#define HV_MIN_DELTA_TICKS 1
/* Routines called by the VMbus driver */
-extern int hv_stimer_alloc(void);
-extern void hv_stimer_free(void);
+extern int hv_stimer_alloc(bool have_percpu_irqs);
extern int hv_stimer_cleanup(unsigned int cpu);
extern void hv_stimer_legacy_init(unsigned int cpu, int sint);
extern void hv_stimer_legacy_cleanup(unsigned int cpu);
--
1.8.3.1