linux-kernel - Re: [PATCH 1/2] KVM: X86: Implement PV IPI in linux guest

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Date:   Fri, 29 Jun 2018 12:10:18 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Wanpeng Li <kernellwp@...il.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>
Subject: Re: [PATCH 1/2] KVM: X86: Implement PV IPI in linux guest

Wanpeng Li <kernellwp@...il.com> writes:

> From: Wanpeng Li <wanpengli@...cent.com>
>
> Implement PV IPIs in guest kernel.
>
> Cc: Paolo Bonzini <pbonzini@...hat.com>
> Cc: Radim Krčmář <rkrcmar@...hat.com>
> Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
> Signed-off-by: Wanpeng Li <wanpengli@...cent.com>
> ---
>  arch/x86/include/uapi/asm/kvm_para.h |  1 +
>  arch/x86/kernel/kvm.c                | 63 ++++++++++++++++++++++++++++++++++++
>  2 files changed, 64 insertions(+)
>
> diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
> index 0ede697..19980ec 100644
> --- a/arch/x86/include/uapi/asm/kvm_para.h
> +++ b/arch/x86/include/uapi/asm/kvm_para.h
> @@ -28,6 +28,7 @@
>  #define KVM_FEATURE_PV_UNHALT		7
>  #define KVM_FEATURE_PV_TLB_FLUSH	9
>  #define KVM_FEATURE_ASYNC_PF_VMEXIT	10
> +#define KVM_FEATURE_PV_SEND_IPI	11
>
>  #define KVM_HINTS_REALTIME      0
>
> diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c
> index 5b2300b..b4f8dc3 100644
> --- a/arch/x86/kernel/kvm.c
> +++ b/arch/x86/kernel/kvm.c
> @@ -454,6 +454,57 @@ static void __init sev_map_percpu_data(void)
>  }
>
>  #ifdef CONFIG_SMP
> +
> +static void __send_ipi_mask(const struct cpumask *mask, int vector)
> +{
> +	unsigned long flags, ipi_bitmap = 0;
> +	int cpu;
> +
> +	local_irq_save(flags);
> +
> +	for_each_cpu(cpu, mask)
> +		__set_bit(per_cpu(x86_cpu_to_apicid, cpu), &ipi_bitmap);

We need a protection against per_cpu(x86_cpu_to_apicid, cpu) > here.

> +	kvm_hypercall2(KVM_HC_SEND_IPI, ipi_bitmap, vector);
> +
> +	local_irq_restore(flags);
> +}
> +
> +static void kvm_send_ipi_mask(const struct cpumask *mask, int vector)
> +{
> +	__send_ipi_mask(mask, vector);
> +}
> +
> +static void kvm_send_ipi_mask_allbutself(const struct cpumask *mask, int vector)
> +{
> +	unsigned int this_cpu = smp_processor_id();
> +	struct cpumask new_mask;
> +	const struct cpumask *local_mask;
> +
> +	cpumask_copy(&new_mask, mask);
> +	cpumask_clear_cpu(this_cpu, &new_mask);
> +	local_mask = &new_mask;
> +	__send_ipi_mask(local_mask, vector);
> +}
> +
> +static void kvm_send_ipi_allbutself(int vector)
> +{
> +	kvm_send_ipi_mask_allbutself(cpu_online_mask, vector);
> +}
> +
> +static void kvm_send_ipi_all(int vector)
> +{
> +	__send_ipi_mask(cpu_online_mask, vector);
> +}
> +
> +static void kvm_setup_pv_ipi(void)
> +{
> +	apic->send_IPI_mask = kvm_send_ipi_mask;
> +	apic->send_IPI_mask_allbutself = kvm_send_ipi_mask_allbutself;
> +	apic->send_IPI_allbutself = kvm_send_ipi_allbutself;
> +	apic->send_IPI_all = kvm_send_ipi_all;
> +	printk("KVM setup pv IPIs\n");
> +}
> +
>  static void __init kvm_smp_prepare_cpus(unsigned int max_cpus)
>  {
>  	native_smp_prepare_cpus(max_cpus);
> @@ -624,12 +675,24 @@ static uint32_t __init kvm_detect(void)
>  	return kvm_cpuid_base();
>  }
>
> +static void __init kvm_apic_init(void)
> +{
> +	if (kvm_para_has_feature(KVM_FEATURE_PV_SEND_IPI))
> +		kvm_setup_pv_ipi();
> +}
> +
> +static void __init kvm_init_platform(void)
> +{
> +	x86_platform.apic_post_init = kvm_apic_init;
> +}
> +
>  const __initconst struct hypervisor_x86 x86_hyper_kvm = {
>  	.name			= "KVM",
>  	.detect			= kvm_detect,
>  	.type			= X86_HYPER_KVM,
>  	.init.guest_late_init	= kvm_guest_init,
>  	.init.x2apic_available	= kvm_para_available,
> +	.init.init_platform 	= kvm_init_platform,
>  };
>
>  static __init int activate_jump_labels(void)

-- 
  Vitaly