Re: [PATCH 4/7] KVM: SVM: Populate FRED event data on event injection

[Paolo Bonzini <pbonzini@redhat.com>]

On 1/29/26 07:36, Shivansh Dhiman wrote:
> From: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
> 
> Set injected-event data (in EVENTINJDATA) when injecting an event,
> use EXITINTDATA for populating the injected-event data during
> reinjection.
> 
> Unlike IDT using some extra CPU register as part of an event
> context, e.g., %cr2 for #PF, FRED saves a complete event context
> in its stack frame, e.g., FRED saves the faulting linear address
> of a #PF into the event data field defined in its stack frame.
> 
> Populate the EVENTINJDATA during event injection. The event data
> will be pushed into a FRED stack frame for VM entries that inject
> an event using FRED event delivery.
> 
> Signed-off-by: Neeraj Upadhyay <Neeraj.Upadhyay@amd.com>
> Co-developed-by: Shivansh Dhiman <shivansh.dhiman@amd.com>
> Signed-off-by: Shivansh Dhiman <shivansh.dhiman@amd.com>
> ---
>   arch/x86/kvm/svm/svm.c | 22 ++++++++++++++++++----
>   1 file changed, 18 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> index ddd8941af6f0..693b46d715b4 100644
> --- a/arch/x86/kvm/svm/svm.c
> +++ b/arch/x86/kvm/svm/svm.c
> @@ -374,6 +374,10 @@ static void svm_inject_exception(struct kvm_vcpu *vcpu)
>   		| SVM_EVTINJ_VALID
>   		| (ex->has_error_code ? SVM_EVTINJ_VALID_ERR : 0)
>   		| SVM_EVTINJ_TYPE_EXEPT;
> +
> +	if (is_fred_enabled(vcpu))
> +		svm->vmcb->control.event_inj_data = ex->event_data;
> +
>   	svm->vmcb->control.event_inj_err = ex->error_code;
>   }
>   
> @@ -4066,7 +4070,7 @@ static void svm_complete_soft_interrupt(struct kvm_vcpu *vcpu, u8 vector,
>   		kvm_rip_write(vcpu, svm->soft_int_old_rip);
>   }
>   
> -static void svm_complete_interrupts(struct kvm_vcpu *vcpu)
> +static void svm_complete_interrupts(struct kvm_vcpu *vcpu, bool reinject_on_vmexit)
>   {
>   	struct vcpu_svm *svm = to_svm(vcpu);
>   	u8 vector;
> @@ -4111,6 +4115,7 @@ static void svm_complete_interrupts(struct kvm_vcpu *vcpu)
>   		break;
>   	case SVM_EXITINTINFO_TYPE_EXEPT: {
>   		u32 error_code = 0;
> +		u64 event_data = 0;
>   
>   		/*
>   		 * Never re-inject a #VC exception.
> @@ -4121,9 +4126,18 @@ static void svm_complete_interrupts(struct kvm_vcpu *vcpu)
>   		if (exitintinfo & SVM_EXITINTINFO_VALID_ERR)
>   			error_code = svm->vmcb->control.exit_int_info_err;
>   
> +		/*
> +		 * FRED requires an additional field to pass injected-event
> +		 * data to the guest.
> +		 */
> +		if (is_fred_enabled(vcpu) && (vector == PF_VECTOR || vector == DB_VECTOR))
> +			event_data = reinject_on_vmexit ?
> +					svm->vmcb->control.exit_int_data :
> +					svm->vmcb->control.event_inj_data;

The new argument is not needed, just...

> @@ -4146,7 +4160,7 @@ static void svm_cancel_injection(struct kvm_vcpu *vcpu)
>   	control->exit_int_info = control->event_inj;
>   	control->exit_int_info_err = control->event_inj_err;

... move event_inj into exit_int here, similar to the other fields:

	control->exit_int_data = control->event_inj_data;

Paolo

>   	control->event_inj = 0;
> -	svm_complete_interrupts(vcpu);
> +	svm_complete_interrupts(vcpu, false);
>   }
>   
>   static int svm_vcpu_pre_run(struct kvm_vcpu *vcpu)
> @@ -4382,7 +4396,7 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags)
>   
>   	trace_kvm_exit(vcpu, KVM_ISA_SVM);
>   
> -	svm_complete_interrupts(vcpu);
> +	svm_complete_interrupts(vcpu, true);
>   
>   	return svm_exit_handlers_fastpath(vcpu);
>   }