From: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> Sent: Monday, March 1, 2021 10:45 AM
>
> On 01/03/2021 02:15, Michael Kelley wrote:
> > 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;
>
> Why not
>
> static DEFINE_PER_CPU(long, stimer0_evt);
>
> no need of allocation /free ?
>
Indeed! I'll make that simplification in v3 of the patch set.
Michael
