Re: [PATCH v5 14/15] KVM: s390: add and wire function gib_alert_irq_handler()

[Michael Mueller <mimu@linux.ibm.com>]

On 03.01.19 16:16, Pierre Morel wrote:
> On 19/12/2018 20:17, Michael Mueller wrote:
>> The patch implements a handler for GIB alert interruptions
>> on the host. Its task is to alert guests that interrupts are
>> pending for them.
>>
>> A GIB alert interrupt statistic counter is added as well:
>>
>> $ cat /proc/interrupts
>>            CPU0       CPU1
>>    ...
>>    GAL:      23         37   [I/O] GIB Alert
>>    ...
>>
>> Signed-off-by: Michael Mueller <mimu@linux.ibm.com>
>> ---
>>   arch/s390/include/asm/irq.h |  1 +
>>   arch/s390/include/asm/isc.h |  1 +
>>   arch/s390/kernel/irq.c      |  1 +
>>   arch/s390/kvm/interrupt.c   | 36 ++++++++++++++++++++++++++++++++++--
>>   4 files changed, 37 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/s390/include/asm/irq.h b/arch/s390/include/asm/irq.h
>> index 2f7f27e5493f..afaf5e3c57fd 100644
>> --- a/arch/s390/include/asm/irq.h
>> +++ b/arch/s390/include/asm/irq.h
>> @@ -62,6 +62,7 @@ enum interruption_class {
>>       IRQIO_MSI,
>>       IRQIO_VIR,
>>       IRQIO_VAI,
>> +    IRQIO_GAL,
>>       NMI_NMI,
>>       CPU_RST,
>>       NR_ARCH_IRQS
>> diff --git a/arch/s390/include/asm/isc.h b/arch/s390/include/asm/isc.h
>> index 6cb9e2ed05b6..b2cc1ec78d06 100644
>> --- a/arch/s390/include/asm/isc.h
>> +++ b/arch/s390/include/asm/isc.h
>> @@ -21,6 +21,7 @@
>>   /* Adapter interrupts. */
>>   #define QDIO_AIRQ_ISC IO_SCH_ISC    /* I/O subchannel in qdio mode */
>>   #define PCI_ISC 2            /* PCI I/O subchannels */
>> +#define GAL_ISC 5            /* GIB alert */
>>   #define AP_ISC 6            /* adjunct processor (crypto) devices */
>>   /* Functions for registration of I/O interruption subclasses */
>> diff --git a/arch/s390/kernel/irq.c b/arch/s390/kernel/irq.c
>> index 0e8d68bac82c..0cd5a5f96729 100644
>> --- a/arch/s390/kernel/irq.c
>> +++ b/arch/s390/kernel/irq.c
>> @@ -88,6 +88,7 @@ static const struct irq_class irqclass_sub_desc[] = {
>>       {.irq = IRQIO_MSI,  .name = "MSI", .desc = "[I/O] MSI Interrupt" },
>>       {.irq = IRQIO_VIR,  .name = "VIR", .desc = "[I/O] Virtual I/O 
>> Devices"},
>>       {.irq = IRQIO_VAI,  .name = "VAI", .desc = "[I/O] Virtual I/O 
>> Devices AI"},
>> +    {.irq = IRQIO_GAL,  .name = "GAL", .desc = "[I/O] GIB Alert"},
>>       {.irq = NMI_NMI,    .name = "NMI", .desc = "[NMI] Machine Check"},
>>       {.irq = CPU_RST,    .name = "RST", .desc = "[CPU] CPU Restart"},
>>   };
>> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
>> index 03e7ba4f215a..79b9c262479b 100644
>> --- a/arch/s390/kvm/interrupt.c
>> +++ b/arch/s390/kvm/interrupt.c
>> @@ -26,6 +26,7 @@
>>   #include <asm/gmap.h>
>>   #include <asm/switch_to.h>
>>   #include <asm/nmi.h>
>> +#include <asm/airq.h>
>>   #include "kvm-s390.h"
>>   #include "gaccess.h"
>>   #include "trace-s390.h"
>> @@ -3043,7 +3044,7 @@ static void __floating_airqs_kick(struct kvm *kvm)
>>   #define NONE_GISA_ADDR 0x00000001UL
>>   #define GISA_ADDR_MASK 0xfffff000UL
>> -static void __maybe_unused process_gib_alert_list(void)
>> +static void process_gib_alert_list(void)
>>   {
>>       u32 final, next_alert, origin = 0UL;
>>       struct kvm_s390_gisa *gisa;
>> @@ -3091,7 +3092,10 @@ void kvm_s390_gisa_clear(struct kvm *kvm)
>>   {
>>       if (!kvm->arch.gisa)
>>           return;
>> +    if (set_iam(kvm->arch.gisa, 0) == -EBUSY)
>> +        process_gib_alert_list();
> 
> We call process_gib_alert_list() from different contexts shouldn't we 
> protect the calls?

That should not be necessary as the xcgh() guarantees that both
instances will work on gib alert lists with disjunctive gisas.

> 
> 
>>       nullify_gisa(kvm->arch.gisa);
>> +    set_iam(kvm->arch.gisa, kvm->arch.iam);
>>       VM_EVENT(kvm, 3, "gisa 0x%pK cleared", kvm->arch.gisa);
>>   }
>> @@ -3111,6 +3115,8 @@ void kvm_s390_gisa_destroy(struct kvm *kvm)
>>   {
>>       if (!kvm->arch.gisa)
>>           return;
>> +    if (set_iam(kvm->arch.gisa, 0) == -EBUSY)
>> +        process_gib_alert_list();
> 
> idem.
> 
>>       kvm->arch.gisa = NULL;
>>   }
>> @@ -3159,11 +3165,23 @@ int kvm_s390_gisc_unregister(struct kvm *kvm, 
>> u32 gisc)
>>   }
>>   EXPORT_SYMBOL_GPL(kvm_s390_gisc_unregister);
>> +static void gib_alert_irq_handler(struct airq_struct *airq)
>> +{
>> +    inc_irq_stat(IRQIO_GAL);
>> +    process_gib_alert_list();
> 
> idem.
> 
>> +}
>> +
>> +static struct airq_struct gib_alert_irq = {
>> +    .handler = gib_alert_irq_handler,
>> +    .lsi_ptr = &gib_alert_irq.lsi_mask,
>> +};
>> +

>