linux-kernel - Re: [RFC PATCH v2 19/69] KVM: x86: Use KVM_BUG/KVM_BUG_ON to handle bugs that are fatal to the VM

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Date:   Tue, 6 Jul 2021 15:47:58 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     isaku.yamahata@...el.com, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        "H . Peter Anvin" <hpa@...or.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Cc:     isaku.yamahata@...il.com,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [RFC PATCH v2 19/69] KVM: x86: Use KVM_BUG/KVM_BUG_ON to handle
 bugs that are fatal to the VM

On 03/07/21 00:04, isaku.yamahata@...el.com wrote:
> From: Sean Christopherson <sean.j.christopherson@...el.com>
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>   arch/x86/kvm/svm/svm.c |  2 +-
>   arch/x86/kvm/vmx/vmx.c | 23 ++++++++++++++---------
>   arch/x86/kvm/x86.c     |  4 ++++
>   3 files changed, 19 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index e088086f3de6..25c72925eb8a 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -1526,7 +1526,7 @@ static void svm_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
>   		load_pdptrs(vcpu, vcpu->arch.walk_mmu, kvm_read_cr3(vcpu));
>   		break;
>   	default:
> -		WARN_ON_ONCE(1);
> +		KVM_BUG_ON(1, vcpu->kvm);
>   	}
>   }
>   
> diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> index d73ba7a6ff8d..6c043a160b30 100644
> --- a/arch/x86/kvm/vmx/vmx.c
> +++ b/arch/x86/kvm/vmx/vmx.c
> @@ -2360,7 +2360,7 @@ static void vmx_cache_reg(struct kvm_vcpu *vcpu, enum kvm_reg reg)
>   		vcpu->arch.cr4 |= vmcs_readl(GUEST_CR4) & guest_owned_bits;
>   		break;
>   	default:
> -		WARN_ON_ONCE(1);
> +		KVM_BUG_ON(1, vcpu->kvm);
>   		break;
>   	}
>   }
> @@ -5062,6 +5062,7 @@ static int handle_cr(struct kvm_vcpu *vcpu)
>   			return kvm_complete_insn_gp(vcpu, err);
>   		case 3:
>   			WARN_ON_ONCE(enable_unrestricted_guest);
> +
>   			err = kvm_set_cr3(vcpu, val);
>   			return kvm_complete_insn_gp(vcpu, err);
>   		case 4:
> @@ -5087,14 +5088,13 @@ static int handle_cr(struct kvm_vcpu *vcpu)
>   		}
>   		break;
>   	case 2: /* clts */
> -		WARN_ONCE(1, "Guest should always own CR0.TS");
> -		vmx_set_cr0(vcpu, kvm_read_cr0_bits(vcpu, ~X86_CR0_TS));
> -		trace_kvm_cr_write(0, kvm_read_cr0(vcpu));
> -		return kvm_skip_emulated_instruction(vcpu);
> +		KVM_BUG(1, vcpu->kvm, "Guest always owns CR0.TS");
> +		return -EIO;
>   	case 1: /*mov from cr*/
>   		switch (cr) {
>   		case 3:
>   			WARN_ON_ONCE(enable_unrestricted_guest);
> +
>   			val = kvm_read_cr3(vcpu);
>   			kvm_register_write(vcpu, reg, val);
>   			trace_kvm_cr_read(cr, val);
> @@ -5404,7 +5404,9 @@ static int handle_ept_misconfig(struct kvm_vcpu *vcpu)
>   
>   static int handle_nmi_window(struct kvm_vcpu *vcpu)
>   {
> -	WARN_ON_ONCE(!enable_vnmi);
> +	if (KVM_BUG_ON(!enable_vnmi, vcpu->kvm))
> +		return -EIO;
> +
>   	exec_controls_clearbit(to_vmx(vcpu), CPU_BASED_NMI_WINDOW_EXITING);
>   	++vcpu->stat.nmi_window_exits;
>   	kvm_make_request(KVM_REQ_EVENT, vcpu);
> @@ -5960,7 +5962,8 @@ static int __vmx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t exit_fastpath)
>   	 * below) should never happen as that means we incorrectly allowed a
>   	 * nested VM-Enter with an invalid vmcs12.
>   	 */
> -	WARN_ON_ONCE(vmx->nested.nested_run_pending);
> +	if (KVM_BUG_ON(vmx->nested.nested_run_pending, vcpu->kvm))
> +		return -EIO;
>   
>   	/* If guest state is invalid, start emulating */
>   	if (vmx->emulation_required)
> @@ -6338,7 +6341,9 @@ static int vmx_sync_pir_to_irr(struct kvm_vcpu *vcpu)
>   	int max_irr;
>   	bool max_irr_updated;
>   
> -	WARN_ON(!vcpu->arch.apicv_active);
> +	if (KVM_BUG_ON(!vcpu->arch.apicv_active, vcpu->kvm))
> +		return -EIO;
> +
>   	if (pi_test_on(&vmx->pi_desc)) {
>   		pi_clear_on(&vmx->pi_desc);
>   		/*
> @@ -6421,7 +6426,7 @@ static void handle_external_interrupt_irqoff(struct kvm_vcpu *vcpu)
>   	unsigned int vector = intr_info & INTR_INFO_VECTOR_MASK;
>   	gate_desc *desc = (gate_desc *)host_idt_base + vector;
>   
> -	if (WARN_ONCE(!is_external_intr(intr_info),
> +	if (KVM_BUG(!is_external_intr(intr_info), vcpu->kvm,
>   	    "KVM: unexpected VM-Exit interrupt info: 0x%x", intr_info))
>   		return;
>   
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index cc45b2c47672..9244d1d560d5 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -9153,6 +9153,10 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>   	}
>   
>   	if (kvm_request_pending(vcpu)) {
> +		if (kvm_check_request(KVM_REQ_VM_BUGGED, vcpu)) {
> +			r = -EIO;
> +			goto out;
> +		}
>   		if (kvm_check_request(KVM_REQ_GET_NESTED_STATE_PAGES, vcpu)) {
>   			if (unlikely(!kvm_x86_ops.nested_ops->get_nested_state_pages(vcpu))) {
>   				r = 0;
> 

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>