Re: [PATCH 15/32] KVM: s390: pci: enable host forwarding of Adapter Event Notifications

[Eric Farman <farman@linux.ibm.com>]

On Tue, 2021-12-07 at 15:57 -0500, Matthew Rosato wrote:
> In cases where interrupts are not forwarded to the guest via
> firmware,
> KVM is responsible for ensuring delivery.  When an interrupt presents
> with the forwarding bit, we must process the forwarding tables until
> all interrupts are delivered.
> 
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>

Nits below regarding 0-vs-NULL, but otherwise:

Reviewed-by: Eric Farman <farman@linux.ibm.com>

> ---
>  arch/s390/include/asm/kvm_host.h |  1 +
>  arch/s390/include/asm/tpi.h      | 14 ++++++
>  arch/s390/kvm/interrupt.c        | 76
> +++++++++++++++++++++++++++++++-
>  arch/s390/kvm/kvm-s390.c         |  3 +-
>  arch/s390/kvm/pci.h              |  9 ++++
>  5 files changed, 101 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/s390/include/asm/kvm_host.h
> b/arch/s390/include/asm/kvm_host.h
> index a604d51acfc8..3f147b8d050b 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -757,6 +757,7 @@ struct kvm_vm_stat {
>  	u64 inject_pfault_done;
>  	u64 inject_service_signal;
>  	u64 inject_virtio;
> +	u64 aen_forward;
>  };
>  
>  struct kvm_arch_memory_slot {
> diff --git a/arch/s390/include/asm/tpi.h
> b/arch/s390/include/asm/tpi.h
> index 1ac538b8cbf5..47a531fdb15b 100644
> --- a/arch/s390/include/asm/tpi.h
> +++ b/arch/s390/include/asm/tpi.h
> @@ -19,6 +19,20 @@ struct tpi_info {
>  	u32 :12;
>  } __packed __aligned(4);
>  
> +/* I/O-Interruption Code as stored by TPI for an Adapter I/O */
> +struct tpi_adapter_info {
> +	u32 :1;
> +	u32 pci:1;
> +	u32 :28;
> +	u32 error:1;
> +	u32 forward:1;
> +	u32 reserved;
> +	u32 adapter_IO:1;
> +	u32 directed_irq:1;
> +	u32 isc:3;
> +	u32 :27;
> +} __packed __aligned(4);
> +
>  #endif /* __ASSEMBLY__ */
>  
>  #endif /* _ASM_S390_TPI_H */
> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
> index 4efe0e95a40f..c6ff871a6ed1 100644
> --- a/arch/s390/kvm/interrupt.c
> +++ b/arch/s390/kvm/interrupt.c
> @@ -3263,11 +3263,85 @@ int kvm_s390_gisc_unregister(struct kvm *kvm,
> u32 gisc)
>  }
>  EXPORT_SYMBOL_GPL(kvm_s390_gisc_unregister);
>  
> +static void aen_host_forward(struct zpci_aift *aift, unsigned long
> si)
> +{
> +	struct kvm_s390_gisa_interrupt *gi;
> +	struct zpci_gaite *gaite;
> +	struct kvm *kvm;
> +
> +	gaite = (struct zpci_gaite *)aift->gait +
> +		(si * sizeof(struct zpci_gaite));
> +	if (gaite->count == 0)
> +		return;
> +	if (gaite->aisb != 0)
> +		set_bit_inv(gaite->aisbo, (unsigned long *)gaite-
> >aisb);
> +
> +	kvm = kvm_s390_pci_si_to_kvm(aift, si);
> +	if (kvm == 0)

if (!kvm)

> +		return;
> +	gi = &kvm->arch.gisa_int;
> +
> +	if (!(gi->origin->g1.simm & AIS_MODE_MASK(gaite->gisc)) ||
> +	    !(gi->origin->g1.nimm & AIS_MODE_MASK(gaite->gisc))) {
> +		gisa_set_ipm_gisc(gi->origin, gaite->gisc);
> +		if (hrtimer_active(&gi->timer))
> +			hrtimer_cancel(&gi->timer);
> +		hrtimer_start(&gi->timer, 0, HRTIMER_MODE_REL);
> +		kvm->stat.aen_forward++;
> +	}
> +}
> +
> +static void aen_process_gait(u8 isc)
> +{
> +	bool found = false, first = true;
> +	union zpci_sic_iib iib = {{0}};
> +	unsigned long si, flags;
> +	struct zpci_aift *aift;
> +
> +	aift = kvm_s390_pci_get_aift();
> +	spin_lock_irqsave(&aift->gait_lock, flags);
> +
> +	if (!aift->gait) {
> +		spin_unlock_irqrestore(&aift->gait_lock, flags);
> +		return;
> +	}
> +
> +	for (si = 0;;) {
> +		/* Scan adapter summary indicator bit vector */
> +		si = airq_iv_scan(aift->sbv, si, airq_iv_end(aift-
> >sbv));
> +		if (si == -1UL) {
> +			if (first || found) {
> +				/* Reenable interrupts. */
> +				if
> (zpci_set_irq_ctrl(SIC_IRQ_MODE_SINGLE, isc,
> +						      &iib))
> +					break;
> +				first = found = false;
> +			} else {
> +				/* Interrupts on and all bits processed
> */
> +				break;
> +			}
> +			found = false;
> +			si = 0;
> +			continue;
> +		}
> +		found = true;
> +		aen_host_forward(aift, si);
> +	}
> +
> +	spin_unlock_irqrestore(&aift->gait_lock, flags);
> +}
> +
>  static void gib_alert_irq_handler(struct airq_struct *airq,
>  				  struct tpi_info *tpi_info)
>  {
> +	struct tpi_adapter_info *info = (struct tpi_adapter_info
> *)tpi_info;
> +
>  	inc_irq_stat(IRQIO_GAL);
> -	process_gib_alert_list();
> +
> +	if (info->forward || info->error)
> +		aen_process_gait(info->isc);
> +	else
> +		process_gib_alert_list();
>  }
>  
>  static struct airq_struct gib_alert_irq = {
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 9cd3c8eb59e8..c8fe9b7c2395 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -65,7 +65,8 @@ const struct _kvm_stats_desc kvm_vm_stats_desc[] =
> {
>  	STATS_DESC_COUNTER(VM, inject_float_mchk),
>  	STATS_DESC_COUNTER(VM, inject_pfault_done),
>  	STATS_DESC_COUNTER(VM, inject_service_signal),
> -	STATS_DESC_COUNTER(VM, inject_virtio)
> +	STATS_DESC_COUNTER(VM, inject_virtio),
> +	STATS_DESC_COUNTER(VM, aen_forward)
>  };
>  
>  const struct kvm_stats_header kvm_vm_stats_header = {
> diff --git a/arch/s390/kvm/pci.h b/arch/s390/kvm/pci.h
> index 74b06d39be3b..776b2745c675 100644
> --- a/arch/s390/kvm/pci.h
> +++ b/arch/s390/kvm/pci.h
> @@ -12,6 +12,7 @@
>  
>  #include <linux/pci.h>
>  #include <linux/mutex.h>
> +#include <linux/kvm_host.h>
>  #include <asm/airq.h>
>  #include <asm/kvm_pci.h>
>  
> @@ -32,6 +33,14 @@ struct zpci_aift {
>  	struct mutex lock; /* Protects the other structures in aift */
>  };
>  
> +static inline struct kvm *kvm_s390_pci_si_to_kvm(struct zpci_aift
> *aift,
> +						 unsigned long si)
> +{
> +	if (aift->kzdev == 0 || aift->kzdev[si] == 0)
> +		return 0;

Check/return NULL

> +	return aift->kzdev[si]->kvm;
> +};
> +
>  struct zpci_aift *kvm_s390_pci_get_aift(void);
>  
>  int kvm_s390_pci_aen_init(u8 nisc);