linux-kernel - Re: [PATCH v10 104/108] KVM: TDX: Silently ignore INIT/SIPI

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Date:   Wed, 23 Nov 2022 23:17:44 +0800
From:   Binbin Wu <binbin.wu@...ux.intel.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Paolo Bonzini <pbonzini@...hat.com>,
        erdemaktas@...gle.com, Sean Christopherson <seanjc@...gle.com>,
        Sagi Shahar <sagis@...gle.com>,
        David Matlack <dmatlack@...gle.com>
Subject: Re: [PATCH v10 104/108] KVM: TDX: Silently ignore INIT/SIPI


On 10/30/2022 2:23 PM, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
>
> The TDX module API doesn't provide API for VMM to inject INIT IPI and SIPI.
> Instead it defines the different protocols to boot application processors.
> Ignore INIT and SIPI events for the TDX guest.
>
> There are two options. 1) (silently) ignore INIT/SIPI request or 2) return
> error to guest TDs somehow.  Given that TDX guest is paravirtualized to
> boot AP, the option 1 is chosen for simplicity.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>   arch/x86/include/asm/kvm-x86-ops.h |  1 +
>   arch/x86/include/asm/kvm_host.h    |  2 ++
>   arch/x86/kvm/lapic.c               | 19 ++++++++++++-------
>   arch/x86/kvm/svm/svm.c             |  1 +
>   arch/x86/kvm/vmx/main.c            | 22 +++++++++++++++++++++-
>   5 files changed, 37 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index 17c3828d42a3..4e9b96480716 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -140,6 +140,7 @@ KVM_X86_OP_OPTIONAL(migrate_timers)
>   KVM_X86_OP(msr_filter_changed)
>   KVM_X86_OP(complete_emulated_msr)
>   KVM_X86_OP(vcpu_deliver_sipi_vector)
> +KVM_X86_OP(vcpu_deliver_init)
>   KVM_X86_OP_OPTIONAL_RET0(vcpu_get_apicv_inhibit_reasons);
>   KVM_X86_OP(check_processor_compatibility)
>   
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 094fff5414e1..df67ca7b23d3 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1706,6 +1706,7 @@ struct kvm_x86_ops {
>   	int (*complete_emulated_msr)(struct kvm_vcpu *vcpu, int err);
>   
>   	void (*vcpu_deliver_sipi_vector)(struct kvm_vcpu *vcpu, u8 vector);
> +	void (*vcpu_deliver_init)(struct kvm_vcpu *vcpu);
>   
>   	/*
>   	 * Returns vCPU specific APICv inhibit reasons
> @@ -1914,6 +1915,7 @@ int kvm_emulate_wbinvd(struct kvm_vcpu *vcpu);
>   void kvm_get_segment(struct kvm_vcpu *vcpu, struct kvm_segment *var, int seg);
>   int kvm_load_segment_descriptor(struct kvm_vcpu *vcpu, u16 selector, int seg);
>   void kvm_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector);
> +void kvm_vcpu_deliver_init(struct kvm_vcpu *vcpu);
>   
>   int kvm_task_switch(struct kvm_vcpu *vcpu, u16 tss_selector, int idt_index,
>   		    int reason, bool has_error_code, u32 error_code);
> diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
> index 7a1d612bd138..7393d858ed72 100644
> --- a/arch/x86/kvm/lapic.c
> +++ b/arch/x86/kvm/lapic.c
> @@ -3035,6 +3035,16 @@ int kvm_lapic_set_pv_eoi(struct kvm_vcpu *vcpu, u64 data, unsigned long len)
>   	return 0;
>   }
>   
> +void kvm_vcpu_deliver_init(struct kvm_vcpu *vcpu)
> +{
> +	kvm_vcpu_reset(vcpu, true);
> +	if (kvm_vcpu_is_bsp(vcpu))
> +		vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> +	else
> +		vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
> +}
> +EXPORT_SYMBOL_GPL(kvm_vcpu_deliver_init);
> +
>   int kvm_apic_accept_events(struct kvm_vcpu *vcpu)
>   {
>   	struct kvm_lapic *apic = vcpu->arch.apic;
> @@ -3066,13 +3076,8 @@ int kvm_apic_accept_events(struct kvm_vcpu *vcpu)
>   		return 0;
>   	}
>   
> -	if (test_and_clear_bit(KVM_APIC_INIT, &apic->pending_events)) {
> -		kvm_vcpu_reset(vcpu, true);
> -		if (kvm_vcpu_is_bsp(apic->vcpu))
> -			vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> -		else
> -			vcpu->arch.mp_state = KVM_MP_STATE_INIT_RECEIVED;
> -	}
> +	if (test_and_clear_bit(KVM_APIC_INIT, &apic->pending_events))
> +		static_call(kvm_x86_vcpu_deliver_init)(vcpu);
>   	if (test_and_clear_bit(KVM_APIC_SIPI, &apic->pending_events)) {
>   		if (vcpu->arch.mp_state == KVM_MP_STATE_INIT_RECEIVED) {
>   			/* evaluate pending_events before reading the vector */
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index 2bcf2e1a5271..5d56b0f1f595 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -4857,6 +4857,7 @@ static struct kvm_x86_ops svm_x86_ops __initdata = {
>   	.complete_emulated_msr = svm_complete_emulated_msr,
>   
>   	.vcpu_deliver_sipi_vector = svm_vcpu_deliver_sipi_vector,
> +	.vcpu_deliver_init = kvm_vcpu_deliver_init,
>   	.vcpu_get_apicv_inhibit_reasons = avic_vcpu_get_apicv_inhibit_reasons,
>   };
>   
> diff --git a/arch/x86/kvm/vmx/main.c b/arch/x86/kvm/vmx/main.c
> index 4acba8d8cb27..d776d5d169d0 100644
> --- a/arch/x86/kvm/vmx/main.c
> +++ b/arch/x86/kvm/vmx/main.c
> @@ -286,6 +286,25 @@ static void vt_deliver_interrupt(struct kvm_lapic *apic, int delivery_mode,
>   	vmx_deliver_interrupt(apic, delivery_mode, trig_mode, vector);
>   }
>   
> +static void vt_vcpu_deliver_sipi_vector(struct kvm_vcpu *vcpu, u8 vector)
> +{
> +	if (is_td_vcpu(vcpu))
> +		return;
> +
> +	kvm_vcpu_deliver_sipi_vector(vcpu, vector);
> +}
> +
> +static void vt_vcpu_deliver_init(struct kvm_vcpu *vcpu)
> +{
> +	if (is_td_vcpu(vcpu)) {
> +		/* TDX doesn't support INIT.  Ignore INIT event */
> +		vcpu->arch.mp_state = KVM_MP_STATE_RUNNABLE;
> +		return;
> +	}
> +
> +	kvm_vcpu_deliver_init(vcpu);
> +}
> +

Is it better to add WARN_ON_ONCE in the above two functions for TD case?


>   static void vt_flush_tlb_all(struct kvm_vcpu *vcpu)
>   {
>   	if (is_td_vcpu(vcpu))
> @@ -627,7 +646,8 @@ struct kvm_x86_ops vt_x86_ops __initdata = {
>   	.msr_filter_changed = vmx_msr_filter_changed,
>   	.complete_emulated_msr = kvm_complete_insn_gp,
>   
> -	.vcpu_deliver_sipi_vector = kvm_vcpu_deliver_sipi_vector,
> +	.vcpu_deliver_sipi_vector = vt_vcpu_deliver_sipi_vector,
> +	.vcpu_deliver_init = vt_vcpu_deliver_init,
>   
>   	.dev_mem_enc_ioctl = tdx_dev_ioctl,
>   	.mem_enc_ioctl = vt_mem_enc_ioctl,