Re: [PATCH v2 1/3] x86/kvm: Don't bother __pv_cpu_mask when !CONFIG_SMP

[Paolo Bonzini]

On 09/04/21 06:18, Wanpeng Li wrote:
> From: Wanpeng Li <wanpengli@xxxxxxxxxxx>
>
> Enable PV TLB shootdown when !CONFIG_SMP doesn't make sense. Let's
> move it inside CONFIG_SMP. In addition, we can avoid define and
> alloc __pv_cpu_mask when !CONFIG_SMP and get rid of 'alloc' variable
> in kvm_alloc_cpumask.
>
> Signed-off-by: Wanpeng Li <wanpengli@xxxxxxxxxxx>
> ---
> v1 -> v2:
>   * shuffle things around a bit more
>
>   arch/x86/kernel/kvm.c | 118 +++++++++++++++++++++++---------------------------
>   1 file changed, 55 insertions(+), 63 deletions(-)
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 5e78e01..224a7a1 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -451,6 +451,10 @@ static void __init sev_map_percpu_data(void)
>   	}
>   }
>   
> +#ifdef CONFIG_SMP
> +
> +static DEFINE_PER_CPU(cpumask_var_t, __pv_cpu_mask);
> +
>   static bool pv_tlb_flush_supported(void)
>   {
>   	return (kvm_para_has_feature(KVM_FEATURE_PV_TLB_FLUSH) &&
> @@ -458,10 +462,6 @@ static bool pv_tlb_flush_supported(void)
>   		kvm_para_has_feature(KVM_FEATURE_STEAL_TIME));
>   }
>   
> -static DEFINE_PER_CPU(cpumask_var_t, __pv_cpu_mask);
> -
> -#ifdef CONFIG_SMP
> -
>   static bool pv_ipi_supported(void)
>   {
>   	return kvm_para_has_feature(KVM_FEATURE_PV_SEND_IPI);
> @@ -574,6 +574,49 @@ static void kvm_smp_send_call_func_ipi(const struct cpumask *mask)
>   	}
>   }
>   
> +static void kvm_flush_tlb_others(const struct cpumask *cpumask,
> +			const struct flush_tlb_info *info)
> +{
> +	u8 state;
> +	int cpu;
> +	struct kvm_steal_time *src;
> +	struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_cpu_mask);
> +
> +	cpumask_copy(flushmask, cpumask);
> +	/*
> +	 * We have to call flush only on online vCPUs. And
> +	 * queue flush_on_enter for pre-empted vCPUs
> +	 */
> +	for_each_cpu(cpu, flushmask) {
> +		src = &per_cpu(steal_time, cpu);
> +		state = READ_ONCE(src->preempted);
> +		if ((state & KVM_VCPU_PREEMPTED)) {
> +			if (try_cmpxchg(&src->preempted, &state,
> +					state | KVM_VCPU_FLUSH_TLB))
> +				__cpumask_clear_cpu(cpu, flushmask);
> +		}
> +	}
> +
> +	native_flush_tlb_others(flushmask, info);
> +}
> +
> +static __init int kvm_alloc_cpumask(void)
> +{
> +	int cpu;
> +
> +	if (!kvm_para_available() || nopv)
> +		return 0;
> +
> +	if (pv_tlb_flush_supported() || pv_ipi_supported())
> +		for_each_possible_cpu(cpu) {
> +			zalloc_cpumask_var_node(per_cpu_ptr(&__pv_cpu_mask, cpu),
> +				GFP_KERNEL, cpu_to_node(cpu));
> +		}
> +
> +	return 0;
> +}
> +arch_initcall(kvm_alloc_cpumask);
> +
>   static void __init kvm_smp_prepare_boot_cpu(void)
>   {
>   	/*
> @@ -611,33 +654,8 @@ static int kvm_cpu_down_prepare(unsigned int cpu)
>   	local_irq_enable();
>   	return 0;
>   }
> -#endif
> -
> -static void kvm_flush_tlb_others(const struct cpumask *cpumask,
> -			const struct flush_tlb_info *info)
> -{
> -	u8 state;
> -	int cpu;
> -	struct kvm_steal_time *src;
> -	struct cpumask *flushmask = this_cpu_cpumask_var_ptr(__pv_cpu_mask);
> -
> -	cpumask_copy(flushmask, cpumask);
> -	/*
> -	 * We have to call flush only on online vCPUs. And
> -	 * queue flush_on_enter for pre-empted vCPUs
> -	 */
> -	for_each_cpu(cpu, flushmask) {
> -		src = &per_cpu(steal_time, cpu);
> -		state = READ_ONCE(src->preempted);
> -		if ((state & KVM_VCPU_PREEMPTED)) {
> -			if (try_cmpxchg(&src->preempted, &state,
> -					state | KVM_VCPU_FLUSH_TLB))
> -				__cpumask_clear_cpu(cpu, flushmask);
> -		}
> -	}
>   
> -	native_flush_tlb_others(flushmask, info);
> -}
> +#endif
>   
>   static void __init kvm_guest_init(void)
>   {
> @@ -653,12 +671,6 @@ static void __init kvm_guest_init(void)
>   		pv_ops.time.steal_clock = kvm_steal_clock;
>   	}
>   
> -	if (pv_tlb_flush_supported()) {
> -		pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
> -		pv_ops.mmu.tlb_remove_table = tlb_remove_table;
> -		pr_info("KVM setup pv remote TLB flush\n");
> -	}
> -
>   	if (kvm_para_has_feature(KVM_FEATURE_PV_EOI))
>   		apic_set_eoi_write(kvm_guest_apic_eoi_write);
>   
> @@ -668,6 +680,12 @@ static void __init kvm_guest_init(void)
>   	}
>   
>   #ifdef CONFIG_SMP
> +	if (pv_tlb_flush_supported()) {
> +		pv_ops.mmu.flush_tlb_others = kvm_flush_tlb_others;
> +		pv_ops.mmu.tlb_remove_table = tlb_remove_table;
> +		pr_info("KVM setup pv remote TLB flush\n");
> +	}
> +
>   	smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
>   	if (pv_sched_yield_supported()) {
>   		smp_ops.send_call_func_ipi = kvm_smp_send_call_func_ipi;
> @@ -734,7 +752,7 @@ static uint32_t __init kvm_detect(void)
>   
>   static void __init kvm_apic_init(void)
>   {
> -#if defined(CONFIG_SMP)
> +#ifdef CONFIG_SMP
>   	if (pv_ipi_supported())
>   		kvm_setup_pv_ipi();
>   #endif
> @@ -794,32 +812,6 @@ static __init int activate_jump_labels(void)
>   }
>   arch_initcall(activate_jump_labels);
>   
> -static __init int kvm_alloc_cpumask(void)
> -{
> -	int cpu;
> -	bool alloc = false;
> -
> -	if (!kvm_para_available() || nopv)
> -		return 0;
> -
> -	if (pv_tlb_flush_supported())
> -		alloc = true;
> -
> -#if defined(CONFIG_SMP)
> -	if (pv_ipi_supported())
> -		alloc = true;
> -#endif
> -
> -	if (alloc)
> -		for_each_possible_cpu(cpu) {
> -			zalloc_cpumask_var_node(per_cpu_ptr(&__pv_cpu_mask, cpu),
> -				GFP_KERNEL, cpu_to_node(cpu));
> -		}
> -
> -	return 0;
> -}
> -arch_initcall(kvm_alloc_cpumask);
> -
>   #ifdef CONFIG_PARAVIRT_SPINLOCKS
>   
>   /* Kick a cpu by its apicid. Used to wake up a halted vcpu */

Queued all three, thanks.

Paolo