Re: [PATCH v2 4/5] KVM: nVMX: Allow to disable VM_{ENTRY_LOAD,EXIT_SAVE}_DEBUG_CONTROLS

From: Bandan Das <bsd@redhat.com>
To: Jan Kiszka <jan.kiszka@siemens.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>, kvm <kvm@vger.kernel.org>
Subject: Re: [PATCH v2 4/5] KVM: nVMX: Allow to disable VM_{ENTRY_LOAD,EXIT_SAVE}_DEBUG_CONTROLS
Date: Mon, 16 Jun 2014 13:02:07 -0400	[thread overview]
Message-ID: <jpg7g4g4wkw.fsf@nelium.bos.redhat.com> (raw)
In-Reply-To: <1d6af71531e07c1f765c116d88c94993b6cedbe3.1402919981.git.jan.kiszka@siemens.com> (Jan Kiszka's message of "Mon, 16 Jun 2014 13:59:43 +0200")

Jan Kiszka <jan.kiszka@siemens.com> writes:

...
>  	/* cpu-based controls */
>  	rdmsr(MSR_IA32_VMX_PROCBASED_CTLS,
>  		nested_vmx_procbased_ctls_low, nested_vmx_procbased_ctls_high);
> @@ -2409,11 +2422,17 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
>  					nested_vmx_procbased_ctls_high);
>  		break;
>  	case MSR_IA32_VMX_TRUE_EXIT_CTLS:
> +		*pdata = vmx_control_msr(nested_vmx_true_exit_ctls_low,
> +					nested_vmx_exit_ctls_high);
> +		break;
>  	case MSR_IA32_VMX_EXIT_CTLS:
>  		*pdata = vmx_control_msr(nested_vmx_exit_ctls_low,
>  					nested_vmx_exit_ctls_high);
>  		break;
>  	case MSR_IA32_VMX_TRUE_ENTRY_CTLS:
> +		*pdata = vmx_control_msr(nested_vmx_true_entry_ctls_low,
> +					nested_vmx_entry_ctls_high);
> +		break;
>  	case MSR_IA32_VMX_ENTRY_CTLS:
>  		*pdata = vmx_control_msr(nested_vmx_entry_ctls_low,
>  					nested_vmx_entry_ctls_high);
> @@ -7836,7 +7855,13 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>  	vmcs_writel(GUEST_GDTR_BASE, vmcs12->guest_gdtr_base);
>  	vmcs_writel(GUEST_IDTR_BASE, vmcs12->guest_idtr_base);
>  
> -	vmcs_write64(GUEST_IA32_DEBUGCTL, vmcs12->guest_ia32_debugctl);
> +	if (vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS) {
> +		kvm_set_dr(vcpu, 7, vmcs12->guest_dr7);
> +		vmcs_write64(GUEST_IA32_DEBUGCTL, vmcs12->guest_ia32_debugctl);
> +	} else {
> +		kvm_set_dr(vcpu, 7, vcpu->arch.dr7);
> +		vmcs_write64(GUEST_IA32_DEBUGCTL, vmx->nested.vmcs01_debugctl);
> +	}

(I guess I don't understand DEBUGCTLS enough) vmcs01_debugctl is used by
L0 to run L1, and if L1 hasn't set VM_ENTRY_LOAD_DEBUG_CONTROLS for L2,
why do we need the GUEST_IA32_DEBUGCTL vmwrite in the "else" case ?

>  	vmcs_write32(VM_ENTRY_INTR_INFO_FIELD,
>  		vmcs12->vm_entry_intr_info_field);
>  	vmcs_write32(VM_ENTRY_EXCEPTION_ERROR_CODE,
> @@ -7846,7 +7871,6 @@ static void prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>  	vmcs_write32(GUEST_INTERRUPTIBILITY_INFO,
>  		vmcs12->guest_interruptibility_info);
>  	vmcs_write32(GUEST_SYSENTER_CS, vmcs12->guest_sysenter_cs);
> -	kvm_set_dr(vcpu, 7, vmcs12->guest_dr7);
>  	vmx_set_rflags(vcpu, vmcs12->guest_rflags);
>  	vmcs_writel(GUEST_PENDING_DBG_EXCEPTIONS,
>  		vmcs12->guest_pending_dbg_exceptions);
> @@ -8143,9 +8167,11 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
>  	    !vmx_control_verify(vmcs12->pin_based_vm_exec_control,
>  	      nested_vmx_pinbased_ctls_low, nested_vmx_pinbased_ctls_high) ||
>  	    !vmx_control_verify(vmcs12->vm_exit_controls,
> -	      nested_vmx_exit_ctls_low, nested_vmx_exit_ctls_high) ||
> +				nested_vmx_true_exit_ctls_low,
> +				nested_vmx_exit_ctls_high) ||
>  	    !vmx_control_verify(vmcs12->vm_entry_controls,
> -	      nested_vmx_entry_ctls_low, nested_vmx_entry_ctls_high))
> +				nested_vmx_true_entry_ctls_low,
> +				nested_vmx_entry_ctls_high))
>  	{
>  		nested_vmx_failValid(vcpu, VMXERR_ENTRY_INVALID_CONTROL_FIELD);
>  		return 1;
> @@ -8222,6 +8248,9 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
>  
>  	vmx->nested.vmcs01_tsc_offset = vmcs_read64(TSC_OFFSET);
>  
> +	if (!(vmcs12->vm_entry_controls & VM_ENTRY_LOAD_DEBUG_CONTROLS))
> +		vmx->nested.vmcs01_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
> +
>  	cpu = get_cpu();
>  	vmx->loaded_vmcs = vmcs02;
>  	vmx_vcpu_put(vcpu);
> @@ -8399,7 +8428,6 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
>  	vmcs12->guest_cr0 = vmcs12_guest_cr0(vcpu, vmcs12);
>  	vmcs12->guest_cr4 = vmcs12_guest_cr4(vcpu, vmcs12);
>  
> -	kvm_get_dr(vcpu, 7, (unsigned long *)&vmcs12->guest_dr7);
>  	vmcs12->guest_rsp = kvm_register_read(vcpu, VCPU_REGS_RSP);
>  	vmcs12->guest_rip = kvm_register_read(vcpu, VCPU_REGS_RIP);
>  	vmcs12->guest_rflags = vmcs_readl(GUEST_RFLAGS);
> @@ -8478,9 +8506,13 @@ static void prepare_vmcs12(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
>  		(vmcs12->vm_entry_controls & ~VM_ENTRY_IA32E_MODE) |
>  		(vm_entry_controls_get(to_vmx(vcpu)) & VM_ENTRY_IA32E_MODE);
>  
> +	if (vmcs12->vm_exit_controls & VM_EXIT_SAVE_DEBUG_CONTROLS) {
> +		kvm_get_dr(vcpu, 7, (unsigned long *)&vmcs12->guest_dr7);
> +		vmcs12->guest_ia32_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
> +	}
> +
>  	/* TODO: These cannot have changed unless we have MSR bitmaps and
>  	 * the relevant bit asks not to trap the change */
> -	vmcs12->guest_ia32_debugctl = vmcs_read64(GUEST_IA32_DEBUGCTL);
>  	if (vmcs12->vm_exit_controls & VM_EXIT_SAVE_IA32_PAT)
>  		vmcs12->guest_ia32_pat = vmcs_read64(GUEST_IA32_PAT);
>  	if (vmcs12->vm_exit_controls & VM_EXIT_SAVE_IA32_EFER)