Re: [PATCH 2/2] KVM : powerpc/booke: Allow debug interrupt injection to guest

[Scott Wood <scottwood@freescale.com>]

On Fri, 2014-06-27 at 11:55 +0530, Bharat Bhushan wrote:
> This patch allow userspace to inject debug interrupt to guest.
> 
> Signed-off-by: Bharat Bhushan <Bharat.Bhushan@freescale.com>

Could you describe how userspace plans to make use of this, and go into
more detail about the changes you're making?

> ---
>  arch/powerpc/kvm/booke.c  | 31 +++++++++++++++++++++++++++++--
>  arch/powerpc/kvm/e500mc.c | 10 +++++++++-
>  2 files changed, 38 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/powerpc/kvm/booke.c b/arch/powerpc/kvm/booke.c
> index bb25937..63ac38c 100644
> --- a/arch/powerpc/kvm/booke.c
> +++ b/arch/powerpc/kvm/booke.c
> @@ -135,6 +135,11 @@ static void kvmppc_vcpu_sync_fpu(struct kvm_vcpu *vcpu)
>  #endif
>  }
>  
> +static int kvmppc_core_pending_debug(struct kvm_vcpu *vcpu)
> +{
> +	return test_bit(BOOKE_IRQPRIO_DEBUG, &vcpu->arch.pending_exceptions);
> +}
> +
>  static void kvmppc_vcpu_sync_debug(struct kvm_vcpu *vcpu)
>  {
>  	/* Synchronize guest's desire to get debug interrupts into shadow MSR */
> @@ -143,8 +148,11 @@ static void kvmppc_vcpu_sync_debug(struct kvm_vcpu *vcpu)
>  	vcpu->arch.shadow_msr |= vcpu->arch.shared->msr & MSR_DE;
>  #endif
>  
> -	/* Force enable debug interrupts when user space wants to debug */
> -	if (vcpu->guest_debug) {
> +	/*
> +	 * Force enable debug interrupts when user space wants to debug
> +	 * and there is no debug interrupt pending for guest to handle.
> +	 */
> +	if (vcpu->guest_debug && !kvmppc_core_pending_debug(vcpu)) {

Are you trying to allow the guest to be simultaneously debugged by
itself and by host userspace?  How does this work?

>  #ifdef CONFIG_KVM_BOOKE_HV
>  		/*
>  		 * Since there is no shadow MSR, sync MSR_DE into the guest
> @@ -264,6 +272,16 @@ static void kvmppc_core_dequeue_watchdog(struct kvm_vcpu *vcpu)
>  	clear_bit(BOOKE_IRQPRIO_WATCHDOG, &vcpu->arch.pending_exceptions);
>  }
>  
> +static void kvmppc_core_queue_debug(struct kvm_vcpu *vcpu)
> +{
> +	kvmppc_booke_queue_irqprio(vcpu, BOOKE_IRQPRIO_DEBUG);
> +}
> +
> +static void kvmppc_core_dequeue_debug(struct kvm_vcpu *vcpu)
> +{
> +	clear_bit(BOOKE_IRQPRIO_DEBUG, &vcpu->arch.pending_exceptions);
> +}

Is there currently no support for a guest debugging itself (i.e.
guest_debug unset) on e500v2?

>  static void set_guest_srr(struct kvm_vcpu *vcpu, unsigned long srr0, u32 srr1)
>  {
>  #ifdef CONFIG_KVM_BOOKE_HV
> @@ -1332,6 +1350,7 @@ static void get_sregs_base(struct kvm_vcpu *vcpu,
>  	sregs->u.e.dec = kvmppc_get_dec(vcpu, tb);
>  	sregs->u.e.tb = tb;
>  	sregs->u.e.vrsave = vcpu->arch.vrsave;
> +	sregs->u.e.dbsr = vcpu->arch.dbsr;
>  }
>  
>  static int set_sregs_base(struct kvm_vcpu *vcpu,
> @@ -1356,6 +1375,14 @@ static int set_sregs_base(struct kvm_vcpu *vcpu,
>  	if (sregs->u.e.update_special & KVM_SREGS_E_UPDATE_TSR)
>  		kvmppc_set_tsr(vcpu, sregs->u.e.tsr);
>  
> +	if (sregs->u.e.update_special & KVM_SREGS_E_UPDATE_DBSR) {
> +		vcpu->arch.dbsr = sregs->u.e.dbsr;
> +		if (vcpu->arch.dbsr)
> +			kvmppc_core_queue_debug(vcpu);
> +		else
> +			kvmppc_core_dequeue_debug(vcpu);
> +	}
> +
>  	return 0;
>  }

one reg?
 
> diff --git a/arch/powerpc/kvm/e500mc.c b/arch/powerpc/kvm/e500mc.c
> index 17e4562..ea724f2 100644
> --- a/arch/powerpc/kvm/e500mc.c
> +++ b/arch/powerpc/kvm/e500mc.c
> @@ -212,7 +212,7 @@ static int kvmppc_core_get_sregs_e500mc(struct kvm_vcpu *vcpu,
>  	struct kvmppc_vcpu_e500 *vcpu_e500 = to_e500(vcpu);
>  
>  	sregs->u.e.features |= KVM_SREGS_E_ARCH206_MMU | KVM_SREGS_E_PM |
> -			       KVM_SREGS_E_PC;
> +			       KVM_SREGS_E_PC | KVM_SREGS_E_ED;
>
>  	sregs->u.e.impl_id = KVM_SREGS_E_IMPL_FSL;
>  
>  	sregs->u.e.impl.fsl.features = 0;
> @@ -220,6 +220,9 @@ static int kvmppc_core_get_sregs_e500mc(struct kvm_vcpu *vcpu,
>  	sregs->u.e.impl.fsl.hid0 = vcpu_e500->hid0;
>  	sregs->u.e.impl.fsl.mcar = vcpu_e500->mcar;
>  
> +	sregs->u.e.dsrr0 = vcpu->arch.dsrr0;
> +	sregs->u.e.dsrr1 = vcpu->arch.dsrr1;
> +
>  	kvmppc_get_sregs_e500_tlb(vcpu, sregs);
>  
>  	sregs->u.e.ivor_high[3] =
> @@ -261,6 +264,11 @@ static int kvmppc_core_set_sregs_e500mc(struct kvm_vcpu *vcpu,
>  			sregs->u.e.ivor_high[5];
>  	}
>  
> +	if (sregs->u.e.features & KVM_SREGS_E_ED) {
> +		vcpu->arch.dsrr0 = sregs->u.e.dsrr0;
> +		vcpu->arch.dsrr1 = sregs->u.e.dsrr1;
> +	}

SPRG9?

-Scott