linux-kernel - Re: [PATCH v3 2/3] KVM: nVMX: Enable VMFUNC for the L1 hypervisor

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Mon, 10 Jul 2017 16:34:51 -0400
From:   Bandan Das <bsd@...hat.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     kvm@...r.kernel.org, pbonzini@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/3] KVM: nVMX: Enable VMFUNC for the L1 hypervisor

David Hildenbrand <david@...hat.com> writes:

>> -	kvm_queue_exception(vcpu, UD_VECTOR);
>> +	struct vcpu_vmx *vmx = to_vmx(vcpu);
>> +	struct vmcs12 *vmcs12;
>> +	u32 function = vcpu->arch.regs[VCPU_REGS_RAX];
>> +
>> +	/*
>> +	 * VMFUNC is only supported for nested guests, but we always enable the
>> +	 * secondary control for simplicity; for non-nested mode, fake that we
>> +	 * didn't by injecting #UD.
>> +	 */
>> +	if (!is_guest_mode(vcpu)) {
>> +		kvm_queue_exception(vcpu, UD_VECTOR);
>> +		return 1;
>> +	}
>> +
>> +	vmcs12 = get_vmcs12(vcpu);
>> +	if ((vmcs12->vm_function_control & (1 << function)) == 0)
>> +		goto fail;
>> +	WARN(1, "VMCS12 VM function control should have been zero");
>
> Should this be a WARN_ONCE?

Even though this line gets removed in patch 3, I agree, it's a
good idea to use WARN_ONCE.

>> +
>> +fail:
>> +	nested_vmx_vmexit(vcpu, vmx->exit_reason,
>> +			  vmcs_read32(VM_EXIT_INTR_INFO),
>> +			  vmcs_readl(EXIT_QUALIFICATION));
>>  	return 1;
>>  }
>>  
>> @@ -10053,7 +10092,8 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
>>  		exec_control &= ~(SECONDARY_EXEC_VIRTUALIZE_APIC_ACCESSES |
>>  				  SECONDARY_EXEC_RDTSCP |
>>  				  SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
>> -				  SECONDARY_EXEC_APIC_REGISTER_VIRT);
>> +				  SECONDARY_EXEC_APIC_REGISTER_VIRT |
>> +				  SECONDARY_EXEC_ENABLE_VMFUNC);
>>  		if (nested_cpu_has(vmcs12,
>>  				   CPU_BASED_ACTIVATE_SECONDARY_CONTROLS)) {
>>  			vmcs12_exec_ctrl = vmcs12->secondary_vm_exec_control &
>> @@ -10061,6 +10101,10 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
>>  			exec_control |= vmcs12_exec_ctrl;
>>  		}
>>  
>> +		/* All VMFUNCs are currently emulated through L0 vmexits.  */
>> +		if (exec_control & SECONDARY_EXEC_ENABLE_VMFUNC)
>> +			vmcs_write64(VM_FUNCTION_CONTROL, 0);
>> +
>>  		if (exec_control & SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY) {
>>  			vmcs_write64(EOI_EXIT_BITMAP0,
>>  				vmcs12->eoi_exit_bitmap0);
>> @@ -10310,6 +10354,11 @@ static int check_vmentry_prereqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
>>  				vmx->nested.nested_vmx_entry_ctls_high))
>>  		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
>>  
>> +	if (nested_cpu_has_vmfunc(vmcs12) &&
>> +	    (vmcs12->vm_function_control &
>> +	     ~vmx->nested.nested_vmx_vmfunc_controls))
>
> I'd prefer the second part on one line, although it will violate 80
> chars. (these variable names really start to get too lengthy to be useful)

Yeah, I had to split it up for that.

Thank you for the quick review!

Bandan

>> +		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
>> +
>>  	if (vmcs12->cr3_target_count > nested_cpu_vmx_misc_cr3_count(vcpu))
>>  		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
>>  
>> 
>
> Feel free to ignore my comments.
>
> Reviewed-by: David Hildenbrand <david@...hat.com>