On 05-08-2021 00:18, Tianyu Lan wrote:
> From: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
>
> Hyper-V Isolation VM doesn't have PIT/HPET legacy timer and only
> provide stimer. Initialize Hyper-v stimer just after enabling
> lapic to avoid kernel stuck during calibrating TSC due to no
> available timer.
>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@xxxxxxxxxxxxx>
> ---
> arch/x86/hyperv/hv_init.c | 29 -----------------------------
> arch/x86/kernel/cpu/mshyperv.c | 22 ++++++++++++++++++++++
> 2 files changed, 22 insertions(+), 29 deletions(-)
>
> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
> index 6f247e7e07eb..4a643a85d570 100644
> --- a/arch/x86/hyperv/hv_init.c
> +++ b/arch/x86/hyperv/hv_init.c
> @@ -271,25 +271,6 @@ static struct syscore_ops hv_syscore_ops = {
> .resume = hv_resume,
> };
>
> -static void (* __initdata old_setup_percpu_clockev)(void);
> -
> -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(false);
> -
> - /*
> - * Still register the LAPIC timer, because the direct-mode STIMER is
> - * not supported by old versions of Hyper-V. This also allows users
> - * to switch to LAPIC timer via /sys, if they want to.
> - */
> - if (old_setup_percpu_clockev)
> - old_setup_percpu_clockev();
> -}
> -
> static void __init hv_get_partition_id(void)
> {
> struct hv_get_partition_id *output_page;
> @@ -396,16 +377,6 @@ void __init hyperv_init(void)
> wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
> }
>
> - /*
> - * hyperv_init() is called before LAPIC is initialized: see
> - * apic_intr_mode_init() -> x86_platform.apic_post_init() and
> - * apic_bsp_setup() -> setup_local_APIC(). The direct-mode STIMER
> - * depends on LAPIC, so hv_stimer_alloc() should be called from
> - * x86_init.timers.setup_percpu_clockev.
> - */
> - old_setup_percpu_clockev = x86_init.timers.setup_percpu_clockev;
> - x86_init.timers.setup_percpu_clockev = hv_stimer_setup_percpu_clockev;
> -
> hv_apic_init();
>
> x86_init.pci.arch_init = hv_pci_init;
> diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c
> index 6b5835a087a3..dcfbd2770d7f 100644
> --- a/arch/x86/kernel/cpu/mshyperv.c
> +++ b/arch/x86/kernel/cpu/mshyperv.c
> @@ -214,6 +214,20 @@ static void __init hv_smp_prepare_boot_cpu(void)
> #endif
> }
>
> +static void (* __initdata old_setup_initr_mode)(void);
> +
> +static void __init hv_setup_initr_mode(void)
> +{
> + if (old_setup_initr_mode)
> + old_setup_initr_mode();
> +
> + /*
> + * The direct-mode STIMER depends on LAPIC and so allocate
> + * STIMER after calling initr node callback.
> + */
> + (void)hv_stimer_alloc(false);
In my understanding, in previous implementation we were ignoring the return error as there was a fallback handling for LAPIC.
However, I'm not seeing the same here, or am I missing something ?
> +}
> +
> static void __init hv_smp_prepare_cpus(unsigned int max_cpus)
> {
> #ifdef CONFIG_X86_64
> @@ -424,6 +438,7 @@ static void __init ms_hyperv_init_platform(void)
> /* Register Hyper-V specific clocksource */
> hv_init_clocksource();
> #endif
> +
> /*
> * TSC should be marked as unstable only after Hyper-V
> * clocksource has been initialized. This ensures that the
> @@ -431,6 +446,13 @@ static void __init ms_hyperv_init_platform(void)
> */
> if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT))
> mark_tsc_unstable("running on Hyper-V");
> +
> + /*
> + * Override initr mode callback in order to allocate STIMER
> + * after initalizing LAPIC.
> + */
> + old_setup_initr_mode = x86_init.irqs.intr_mode_init;
> + x86_init.irqs.intr_mode_init = hv_setup_initr_mode;
> }
>
> static bool __init ms_hyperv_x2apic_available(void)
>
Regards,
~Praveen.
