Hi, Bibo,
On Mon, Nov 24, 2025 at 11:54 AM Bibo Mao <[email protected]> wrote:
>
> Function vcpu_is_preempted() is used to check whether vCPU is preempted
> or not. Here add implementation with vcpu_is_preempted() when option
> CONFIG_PARAVIRT is enabled.
>
> Signed-off-by: Bibo Mao <[email protected]>
> ---
> arch/loongarch/include/asm/qspinlock.h | 5 +++++
> arch/loongarch/kernel/paravirt.c | 16 ++++++++++++++++
> 2 files changed, 21 insertions(+)
>
> diff --git a/arch/loongarch/include/asm/qspinlock.h
> b/arch/loongarch/include/asm/qspinlock.h
> index e76d3aa1e1eb..9a5b7ba1f4cb 100644
> --- a/arch/loongarch/include/asm/qspinlock.h
> +++ b/arch/loongarch/include/asm/qspinlock.h
> @@ -34,6 +34,11 @@ static inline bool virt_spin_lock(struct qspinlock *lock)
> return true;
> }
>
> +#ifdef CONFIG_SMP
> +#define vcpu_is_preempted vcpu_is_preempted
> +bool vcpu_is_preempted(int cpu);
In V1 there is a build error because you reference mp_ops, so in V2
you needn't put it in CONFIG_SMP.
On the other hand, even if you really build a UP guest kernel, when
multiple guests run together, you probably need vcpu_is_preemtped.
Huacai
> +#endif
> +
> #endif /* CONFIG_PARAVIRT */
>
> #include <asm-generic/qspinlock.h>
> diff --git a/arch/loongarch/kernel/paravirt.c
> b/arch/loongarch/kernel/paravirt.c
> index b1b51f920b23..d4163679adc4 100644
> --- a/arch/loongarch/kernel/paravirt.c
> +++ b/arch/loongarch/kernel/paravirt.c
> @@ -246,6 +246,7 @@ static void pv_disable_steal_time(void)
> }
>
> #ifdef CONFIG_SMP
> +DEFINE_STATIC_KEY_FALSE(virt_preempt_key);
> static int pv_time_cpu_online(unsigned int cpu)
> {
> unsigned long flags;
> @@ -267,6 +268,18 @@ static int pv_time_cpu_down_prepare(unsigned int cpu)
>
> return 0;
> }
> +
> +bool notrace vcpu_is_preempted(int cpu)
> +{
> + struct kvm_steal_time *src;
> +
> + if (!static_branch_unlikely(&virt_preempt_key))
> + return false;
> +
> + src = &per_cpu(steal_time, cpu);
> + return !!(src->preempted & KVM_VCPU_PREEMPTED);
> +}
> +EXPORT_SYMBOL(vcpu_is_preempted);
> #endif
>
> static void pv_cpu_reboot(void *unused)
> @@ -308,6 +321,9 @@ int __init pv_time_init(void)
> pr_err("Failed to install cpu hotplug callbacks\n");
> return r;
> }
> +
> + if (kvm_para_has_feature(KVM_FEATURE_PREEMPT))
> + static_branch_enable(&virt_preempt_key);
> #endif
>
> static_call_update(pv_steal_clock, paravt_steal_clock);
> --
> 2.39.3
>
