Re: [PATCH 1/2] KVM: x86: Add emulation support for #GP triggered by VM instructions

[Bandan Das]

Sean Christopherson <seanjc@xxxxxxxxxx> writes:
...
>> -	if ((emulation_type & EMULTYPE_VMWARE_GP) &&
>> -	    !is_vmware_backdoor_opcode(ctxt)) {
>> -		kvm_queue_exception_e(vcpu, GP_VECTOR, 0);
>> -		return 1;
>> +	if (emulation_type & EMULTYPE_PARAVIRT_GP) {
>> +		vminstr = is_vm_instr_opcode(ctxt);
>> +		if (!vminstr && !is_vmware_backdoor_opcode(ctxt)) {
>> +			kvm_queue_exception_e(vcpu, GP_VECTOR, 0);
>> +			return 1;
>> +		}
>> +		if (vminstr)
>> +			return vminstr;
>
> I'm pretty sure this doesn't correctly handle a VM-instr in L2 that hits a bad
> L0 GPA and that L1 wants to intercept.  The intercept bitmap isn't checked until
> x86_emulate_insn(), and the vm*_interception() helpers expect nested VM-Exits to
> be handled further up the stack.
>
So, the condition is that L2 executes a vmload and #GPs on a reserved address, jumps to L0 - L0 doesn't
check if L1 has asked for the instruction to be intercepted and goes on with emulating
vmload and returning back to L2 ?

>>  	}
>>  
>>  	/*
>> -- 
>> 2.27.0
>>