Hi, Bibo, On Tue, Dec 2, 2025 at 10:48 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 | 3 +++ > arch/loongarch/kernel/paravirt.c | 23 ++++++++++++++++++++++- > 2 files changed, 25 insertions(+), 1 deletion(-) > > diff --git a/arch/loongarch/include/asm/qspinlock.h > b/arch/loongarch/include/asm/qspinlock.h > index e76d3aa1e1eb..fa3eaf7e48f2 100644 > --- a/arch/loongarch/include/asm/qspinlock.h > +++ b/arch/loongarch/include/asm/qspinlock.h > @@ -34,6 +34,9 @@ static inline bool virt_spin_lock(struct qspinlock *lock) > return true; > } > > +#define vcpu_is_preempted vcpu_is_preempted > +bool vcpu_is_preempted(int cpu); > + > #endif /* CONFIG_PARAVIRT */ > > #include <asm-generic/qspinlock.h> > diff --git a/arch/loongarch/kernel/paravirt.c > b/arch/loongarch/kernel/paravirt.c > index b1b51f920b23..b61a93c6aec8 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 > +static 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); > @@ -318,7 +334,12 @@ int __init pv_time_init(void) > static_key_slow_inc(¶virt_steal_rq_enabled); > #endif > > - pr_info("Using paravirt steal-time\n"); > +#ifdef CONFIG_SMP
Linux kernel is removing non-SMP step by step [1]. https://kernelnewbies.org/Linux_6.17#Unconditionally_compile_task_scheduler_with_SMP_support Though we cannot remove all "#ifdef CONFIG_SMP" at present, we can at least stop adding more. So I prefer to make this whole patch out of CONFIG_SMP. But if you don't like this, you can at least move the virt_preempt_key declaration out of "#ifdef CONFIG_SMP", then the #ifdefs here can be removed. Huacai > + if (static_key_enabled(&virt_preempt_key)) > + pr_info("Using paravirt steal-time with preempt enabled\n"); > + else > +#endif > + pr_info("Using paravirt steal-time with preempt disabled\n"); > > return 0; > } > -- > 2.39.3 > >
