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Message-ID: <ae7c65d8-f632-a7f4-926a-50b9660673a1@linux.ibm.com>
Date:   Mon, 7 Feb 2022 18:09:49 +0100
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Subject: Re: [PATCH] KVM: s390: pv: make use of ultravisor AIV support
Content-Language: en-US
To:     Janosch Frank <frankja@linux.ibm.com>, kvm@vger.kernel.org
Cc:     cohuck@redhat.com, borntraeger@de.ibm.com, thuth@redhat.com,
        pasic@linux.ibm.com, david@redhat.com, linux-s390@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20220204085203.3490425-1-mimu@linux.ibm.com>
 <d986a43b-5828-8145-ff91-1a507434de8b@linux.ibm.com>
From:   Michael Mueller <mimu@linux.ibm.com>
In-Reply-To: <d986a43b-5828-8145-ff91-1a507434de8b@linux.ibm.com>
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On 04.02.22 12:12, Janosch Frank wrote:
> On 2/4/22 09:52, Michael Mueller wrote:
>> This patch enables the ultravisor adapter interruption vitualization
>> support indicated by UV feature BIT_UV_FEAT_AIV. This allows ISC
>> interruption injection directly into the GISA IPM for PV kvm guests.
>>
>> Hardware that does not support this feature will continue to use the
>> UV interruption interception method to deliver ISC interruptions to
>> PV kvm guests. For this purpose, the ECA_AIV bit for all guest cpus
>> will be cleared and the GISA will be disabled during PV guest setup.
>>
>> In addition a check in __inject_io() has been removed. That reduces the
>> required intructions for interruption handling for PV and traditional
>> kvm guests.
>>
>> Signed-off-by: Michael Mueller <mimu@linux.ibm.com>
>> ---
>>   arch/s390/include/asm/uv.h |  1 +
>>   arch/s390/kvm/interrupt.c  | 53 +++++++++++++++++++++++++++++++++-----
>>   arch/s390/kvm/kvm-s390.c   | 10 ++++---
>>   arch/s390/kvm/kvm-s390.h   | 11 ++++++++
>>   4 files changed, 66 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
>> index 72d3e49c2860..0cb2bbb50ad7 100644
>> --- a/arch/s390/include/asm/uv.h
>> +++ b/arch/s390/include/asm/uv.h
>> @@ -80,6 +80,7 @@ enum uv_cmds_inst {
>>   enum uv_feat_ind {
>>       BIT_UV_FEAT_MISC = 0,
>> +    BIT_UV_FEAT_AIV = 1,
>>   };
>>   struct uv_cb_header {
>> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c
>> index c3bd993fdd0c..6ff80069b1fe 100644
>> --- a/arch/s390/kvm/interrupt.c
>> +++ b/arch/s390/kvm/interrupt.c
>> @@ -1900,13 +1900,12 @@ static int __inject_io(struct kvm *kvm, struct 
>> kvm_s390_interrupt_info *inti)
>>       isc = int_word_to_isc(inti->io.io_int_word);
>>       /*
>> -     * Do not make use of gisa in protected mode. We do not use the lock
>> -     * checking variant as this is just a performance optimization 
>> and we
>> -     * do not hold the lock here. This is ok as the code will pick
>> -     * interrupts from both "lists" for delivery.
>> +     * We do not use the lock checking variant as this is just a
>> +     * performance optimization and we do not hold the lock here.
>> +     * This is ok as the code will pick interrupts from both "lists"
>> +     * for delivery.
>>        */
>> -    if (!kvm_s390_pv_get_handle(kvm) &&
>> -        gi->origin && inti->type & KVM_S390_INT_IO_AI_MASK) {
>> +    if (gi->origin && inti->type & KVM_S390_INT_IO_AI_MASK) {
> 
> This was previously fenced by the UV by ignoring the gd altogether, right?

Right, the z15 UV is ignoring gd altogether. That's the reason
we made the exception for PV guests here. That is now released
and included in the gd value (i.e. gi->origin)

> 
>>           VM_EVENT(kvm, 4, "%s isc %1u", "inject: I/O (AI/gisa)", isc);
>>           gisa_set_ipm_gisc(gi->origin, isc);
>>           kfree(inti);
>> @@ -3163,9 +3162,32 @@ void kvm_s390_gisa_init(struct kvm *kvm)
>>       VM_EVENT(kvm, 3, "gisa 0x%pK initialized", gi->origin);
>>   }
>> +void kvm_s390_gisa_enable(struct kvm *kvm)
>> +{
>> +    struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
>> +    struct kvm_vcpu *vcpu;
>> +    int i;
>> +
>> +    if (gi->origin)
>> +        return;
>> +    kvm_s390_gisa_init(kvm);
>> +    kvm_for_each_vcpu(i, vcpu, kvm) {
>> +        mutex_lock(&vcpu->mutex);
>> +        vcpu->arch.sie_block->gd = kvm_s390_get_gisa_desc(kvm);
>> +        if (vcpu->arch.sie_block->gd) {
>> +            vcpu->arch.sie_block->eca |= ECA_AIV;
>> +            VCPU_EVENT(vcpu, 3, "AIV gisa format-%u enabled for cpu 
>> %03u",
>> +                   vcpu->arch.sie_block->gd & 0x3, vcpu->vcpu_id);
>> +        }
>> +        mutex_unlock(&vcpu->mutex);
>> +    }
>> +}
>> +
>> +
>>   void kvm_s390_gisa_destroy(struct kvm *kvm)
>>   {
>>       struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
>> +    struct kvm_s390_gisa *gisa = gi->origin;
>>       if (!gi->origin)
>>           return;
>> @@ -3176,6 +3198,25 @@ void kvm_s390_gisa_destroy(struct kvm *kvm)
>>           cpu_relax();
>>       hrtimer_cancel(&gi->timer);
>>       gi->origin = NULL;
>> +    VM_EVENT(kvm, 3, "gisa 0x%pK destroyed", gisa);
>> +}
>> +
>> +void kvm_s390_gisa_disable(struct kvm *kvm)
>> +{
>> +    struct kvm_s390_gisa_interrupt *gi = &kvm->arch.gisa_int;
>> +    struct kvm_vcpu *vcpu;
>> +    int i;
>> +
>> +    if (!gi->origin)
>> +        return;
>> +    kvm_for_each_vcpu(i, vcpu, kvm) {
>> +        mutex_lock(&vcpu->mutex);
>> +        vcpu->arch.sie_block->eca &= ~ECA_AIV;
>> +        vcpu->arch.sie_block->gd = 0U;
>> +        mutex_unlock(&vcpu->mutex);
>> +        VCPU_EVENT(vcpu, 3, "AIV disabled for cpu %03u", vcpu->vcpu_id);
>> +    }
>> +    kvm_s390_gisa_destroy(kvm);
>>   }
>>   /**
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index 14a18ba5ff2c..8839a58e03c7 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -2273,6 +2273,9 @@ static int kvm_s390_handle_pv(struct kvm *kvm, 
>> struct kvm_pv_cmd *cmd)
>>           if (r)
>>               break;
>> +        if (!test_bit_inv(BIT_UV_FEAT_AIV, 
>> &uv_info.uv_feature_indications))
>> +            kvm_s390_gisa_disable(kvm);
>> +
> 
> If the kvm_s390_cpus_to_pv() fails we'd miss a gisa_enable(), no? >
> And we might have a problem in kvm_s390_vcpu_setup() as we don't fence 
> it for new cpus.

I guess we then need it for both failing cases pv_init_vm()
and cpus_to_pv(). But I have to verify with UVC_CMD_CREATE_SEC_CONF.
It might be possible to disable the gisa after that UVC call.

> 
> 
>>           r = kvm_s390_pv_init_vm(kvm, &cmd->rc, &cmd->rrc);
>>           if (r)
>>               break;
>> @@ -2300,6 +2303,9 @@ static int kvm_s390_handle_pv(struct kvm *kvm, 
>> struct kvm_pv_cmd *cmd)
>>               break;
>>           r = kvm_s390_pv_deinit_vm(kvm, &cmd->rc, &cmd->rrc);
>> +        if (use_gisa)
>> +            kvm_s390_gisa_enable(kvm);
>> +
>>           /* no need to block service interrupts any more */
>>           clear_bit(IRQ_PEND_EXT_SERVICE, 
>> &kvm->arch.float_int.masked_irqs);
>>           break;
>> @@ -3309,9 +3315,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
>>       vcpu->arch.sie_block->icpua = vcpu->vcpu_id;
>>       spin_lock_init(&vcpu->arch.local_int.lock);
>> -    vcpu->arch.sie_block->gd = 
>> (u32)(u64)vcpu->kvm->arch.gisa_int.origin;
>> -    if (vcpu->arch.sie_block->gd && sclp.has_gisaf)
>> -        vcpu->arch.sie_block->gd |= GISA_FORMAT1;
>> +    vcpu->arch.sie_block->gd = kvm_s390_get_gisa_desc(vcpu->kvm);
>>       seqcount_init(&vcpu->arch.cputm_seqcount);
>>       vcpu->arch.pfault_token = KVM_S390_PFAULT_TOKEN_INVALID;
>> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
>> index c07a050d757d..08a622a44f6f 100644
>> --- a/arch/s390/kvm/kvm-s390.h
>> +++ b/arch/s390/kvm/kvm-s390.h
>> @@ -217,6 +217,15 @@ static inline void 
>> kvm_s390_set_user_cpu_state_ctrl(struct kvm *kvm)
>>       kvm->arch.user_cpu_state_ctrl = 1;
>>   }
>> +static inline u32 kvm_s390_get_gisa_desc(struct kvm *kvm)
>> +{
>> +    u32 gd = (u32)(u64)kvm->arch.gisa_int.origin;
>> +
>> +    if (gd && sclp.has_gisaf)
>> +        gd |= GISA_FORMAT1;
>> +    return gd;
>> +}
>> +
>>   /* implemented in pv.c */
>>   int kvm_s390_pv_destroy_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc);
>>   int kvm_s390_pv_create_cpu(struct kvm_vcpu *vcpu, u16 *rc, u16 *rrc);
>> @@ -435,6 +444,8 @@ int kvm_s390_get_irq_state(struct kvm_vcpu *vcpu,
>>   void kvm_s390_gisa_init(struct kvm *kvm);
>>   void kvm_s390_gisa_clear(struct kvm *kvm);
>>   void kvm_s390_gisa_destroy(struct kvm *kvm);
>> +void kvm_s390_gisa_disable(struct kvm *kvm);
>> +void kvm_s390_gisa_enable(struct kvm *kvm);
>>   int kvm_s390_gib_init(u8 nisc);
>>   void kvm_s390_gib_destroy(void);
>>
>