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Date: Mon, 28 Jan 2019 17:04:10 +0100
From: Michael Mueller <mimu@...ux.ibm.com>
To: pmorel@...ux.ibm.com, KVM Mailing List <kvm@...r.kernel.org>
Cc: Linux-S390 Mailing List <linux-s390@...r.kernel.org>,
linux-kernel@...r.kernel.org,
Martin Schwidefsky <schwidefsky@...ibm.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Janosch Frank <frankja@...ux.ibm.com>,
David Hildenbrand <david@...hat.com>,
Cornelia Huck <cohuck@...hat.com>,
Halil Pasic <pasic@...ux.ibm.com>
Subject: Re: [PATCH v6 11/13] KVM: s390: add functions to (un)register GISC
with GISA
On 28.01.19 16:45, Pierre Morel wrote:
> On 24/01/2019 13:59, Michael Mueller wrote:
>> Add the Interruption Alert Mask (IAM) to the architecture specific
>> kvm struct. This mask in the GISA is used to define for which ISC
>> a GIB alert will be issued.
>>
>> The functions kvm_s390_gisc_register() and kvm_s390_gisc_unregister()
>> are used to (un)register a GISC (guest ISC) with a virtual machine and
>> its GISA.
>>
>> Upon successful completion, kvm_s390_gisc_register() returns the
>> ISC to be used for GIB alert interruptions. A negative return code
>> indicates an error during registration.
>>
>> Theses functions will be used by other adapter types like AP and PCI to
>> request pass-through interruption support.
>>
>> Signed-off-by: Michael Mueller <mimu@...ux.ibm.com>
>> ---
>> arch/s390/include/asm/kvm_host.h | 13 +++++
>> arch/s390/kvm/interrupt.c | 117
>> +++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 130 insertions(+)
>>
>> diff --git a/arch/s390/include/asm/kvm_host.h
>> b/arch/s390/include/asm/kvm_host.h
>> index 7077762ab460..2cfff617cb21 100644
>> --- a/arch/s390/include/asm/kvm_host.h
>> +++ b/arch/s390/include/asm/kvm_host.h
>> @@ -781,6 +781,9 @@ struct kvm_s390_gisa {
>> u8 reserved03[11];
>> u32 airq_count;
>> } g1;
>> + struct {
>> + u64 word[4];
>> + } u64;
>> };
>> };
>> @@ -813,8 +816,15 @@ struct kvm_s390_vsie {
>> struct page *pages[KVM_MAX_VCPUS];
>> };
>> +struct kvm_s390_gisa_iam {
>> + u8 mask;
>> + spinlock_t ref_lock;
>> + u32 ref_count[MAX_ISC + 1];
>> +};
>> +
>> struct kvm_s390_gisa_interrupt {
>> struct kvm_s390_gisa *origin;
>> + struct kvm_s390_gisa_iam alert;
>> };
>> struct kvm_arch{
>> @@ -885,6 +895,9 @@ void kvm_arch_crypto_set_masks(struct kvm *kvm,
>> unsigned long *apm,
>> extern int sie64a(struct kvm_s390_sie_block *, u64 *);
>> extern char sie_exit;
>> +extern int kvm_s390_gisc_register(struct kvm *kvm, u32 gisc);
>> +extern int kvm_s390_gisc_unregister(struct kvm *kvm, u32 gisc);
>> +
>> static inline void kvm_arch_hardware_disable(void) {}
>> static inline void kvm_arch_check_processor_compat(void *rtn) {}
>> static inline void kvm_arch_sync_events(struct kvm *kvm) {}
>> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
>> index 5efcd9e2cf8f..6bc9dab6d352 100644
>> --- a/arch/s390/kvm/interrupt.c
>> +++ b/arch/s390/kvm/interrupt.c
>> @@ -222,6 +222,33 @@ static inline u8 int_word_to_isc(u32 int_word)
>> */
>> #define IPM_BIT_OFFSET (offsetof(struct kvm_s390_gisa, ipm) *
>> BITS_PER_BYTE)
>> +/**
>> + * gisa_set_iam - change the GISA interruption alert mask
>> + *
>> + * @gisa: gisa to operate on
>> + * @iam: new IAM value to use
>> + *
>> + * Change the IAM atomically with the next alert address and the IPM
>> + * of the GISA if the GISA is not part of the GIB alert list. All three
>> + * fields are located in the first long word of the GISA.
>> + *
>> + * Returns: 0 on success
>> + * -EBUSY in case the gisa is part of the alert list
>> + */
>> +static inline int gisa_set_iam(struct kvm_s390_gisa *gisa, u8 iam)
>> +{
>> + u64 word, _word;
>> +
>> + do {
>> + word = READ_ONCE(gisa->u64.word[0]);
>> + if ((u64)gisa != word >> 32)
>> + return -EBUSY;
>> + _word = (word & ~0xffUL) | iam;
>> + } while (cmpxchg(&gisa->u64.word[0], word, _word) != word);
>> +
>> + return 0;
>> +}
>> +
>> static inline void gisa_set_ipm_gisc(struct kvm_s390_gisa *gisa, u32
>> gisc)
>> {
>> set_bit_inv(IPM_BIT_OFFSET + gisc, (unsigned long *) gisa);
>> @@ -2911,6 +2938,8 @@ void kvm_s390_gisa_init(struct kvm *kvm)
>> if (!css_general_characteristics.aiv)
>> return;
>> gi->origin = &kvm->arch.sie_page2->gisa;
>> + gi->alert.mask = 0;
>> + spin_lock_init(&gi->alert.ref_lock);
>> kvm_s390_gisa_clear(kvm);
>> VM_EVENT(kvm, 3, "gisa 0x%pK initialized", gi->origin);
>> }
>> @@ -2920,6 +2949,94 @@ void kvm_s390_gisa_destroy(struct kvm *kvm)
>> kvm->arch.gisa_int.origin = NULL;
>> }
>> +/**
>> + * kvm_s390_gisc_register - register a guest ISC
>> + *
>> + * @kvm: the kernel vm to work with
>> + * @gisc: the guest interruption sub class to register
>> + *
>> + * The function extends the vm specific alert mask to use.
>> + * The effectve IAM mask in the GISA is updated as well
>> + * in case the GISA is not part of the GIB alert list.
>> + * It will be updated latest when the IAM gets restored
>> + * by gisa_get_ipm_or_restore_iam().
>> + *
>> + * Returns: the nonspecific ISC (NISC) the gib alert mechanism
>> + * has registered with the channel subsystem.
>> + * -ENODEV in case the vm uses no GISA
>> + * -ERANGE in case the guest ISC is invalid
>> + */
>> +int kvm_s390_gisc_register(struct kvm *kvm, u32 gisc)
>> +{
>> + struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
>> + u8 alert_mask;
>> +
>> + if (!gi->origin)
>> + return -ENODEV;
>> + if (gisc > MAX_ISC)
>> + return -ERANGE;
>> +
>> + spin_lock(&gi->alert.ref_lock);
>> + if (gi->alert.ref_count[gisc] == 0) {
>> + alert_mask = gi->alert.mask | 0x80 >> gisc;
>> + WRITE_ONCE(gi->alert.mask, alert_mask);
>
> not sure WRITE_ONCE is useful.
I dropped that in both routines.
>
>
>
>> + }
>> + gi->alert.ref_count[gisc]++;
>> + if (gi->alert.ref_count[gisc] == 1)
>> + gisa_set_iam(gi->origin, alert_mask);
>
> This will trigger a GAL interrupt on first AP interrupt in all cases.
> However setting the iam here is simple and the price is not so high.
> so... without the WRITE_ONCE in register and in unregister:
>
> Acked-by: Pierre Morel<pmorel@...ux.ibm.com>
>
> Pierre
>
Cheers,
Michael
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