Re: [PATCH v6 24/25] KVM: nVMX: Introduce new VMX_BASIC bit for event error_code delivery to L1

[Sean Christopherson <seanjc@google.com>]

On Wed, Nov 15, 2023, Weijiang Yang wrote:
> On 11/1/2023 12:21 PM, Chao Gao wrote:
> > On Thu, Sep 14, 2023 at 02:33:24AM -0400, Yang Weijiang wrote:
> > > @@ -2846,12 +2846,16 @@ static int nested_check_vm_entry_controls(struct kvm_vcpu *vcpu,
> > > 		    CC(intr_type == INTR_TYPE_OTHER_EVENT && vector != 0))
> > > 			return -EINVAL;
> > > 
> > > -		/* VM-entry interruption-info field: deliver error code */
> > > -		should_have_error_code =
> > > -			intr_type == INTR_TYPE_HARD_EXCEPTION && prot_mode &&
> > > -			x86_exception_has_error_code(vector);
> > > -		if (CC(has_error_code != should_have_error_code))
> > > -			return -EINVAL;
> > > +		if (!prot_mode || intr_type != INTR_TYPE_HARD_EXCEPTION ||
> > > +		    !nested_cpu_has_no_hw_errcode_cc(vcpu)) {
> > > +			/* VM-entry interruption-info field: deliver error code */
> > > +			should_have_error_code =
> > > +				intr_type == INTR_TYPE_HARD_EXCEPTION &&
> > > +				prot_mode &&
> > > +				x86_exception_has_error_code(vector);
> > > +			if (CC(has_error_code != should_have_error_code))
> > > +				return -EINVAL;
> > > +		}
> > prot_mode and intr_type are used twice, making the code a little hard to read.
> > 
> > how about:
> > 		/*
> > 		 * Cannot deliver error code in real mode or if the
> > 		 * interruption type is not hardware exception. For other
> > 		 * cases, do the consistency check only if the vCPU doesn't
> > 		 * enumerate VMX_BASIC_NO_HW_ERROR_CODE_CC.
> > 		 */
> > 		if (!prot_mode || intr_type != INTR_TYPE_HARD_EXCEPTION) {
> > 			if (CC(has_error_code))
> > 				return -EINVAL;
> > 		} else if (!nested_cpu_has_no_hw_errcode_cc(vcpu)) {
> > 			if (CC(has_error_code != x86_exception_has_error_code(vector)))
> > 				return -EINVAL;
> > 		}

Or maybe go one step further and put the nested_cpu_has...() check inside the CC()
macro so that it too will be captured on error.  It's a little uglier though, and
I doubt providing that extra information will matter in practice, so definitely
feel free to stick with Chao's version.

		if (!prot_mode || intr_type != INTR_TYPE_HARD_EXCEPTION) {
			if (CC(has_error_code))
				return -EINVAL;
		} else if (CC(!nested_cpu_has_no_hw_errcode_cc(vcpu) &&
			      has_error_code != x86_exception_has_error_code(vector))) {
			return -EINVAL;
		}