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Message-ID: <9d21f70f-969a-5752-1027-acd6fbfcce12@linux.ibm.com>
Date: Wed, 9 Feb 2022 13:26:55 +0100
From: Michael Mueller <mimu@...ux.ibm.com>
To: Janosch Frank <frankja@...ux.ibm.com>, kvm@...r.kernel.org
Cc: cohuck@...hat.com, borntraeger@...ibm.com, thuth@...hat.com,
pasic@...ux.ibm.com, david@...hat.com, linux-s390@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] KVM: s390: pv: make use of ultravisor AIV support
On 09.02.22 10:12, Janosch Frank wrote:
> On 2/8/22 17:53, 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 CPU setup.
>>
>> In addition a check in __inject_io() has been removed. That reduces the
>> required instructions for interruption handling for PV and traditional
>> kvm guests.
>>
>> Signed-off-by: Michael Mueller <mimu@...ux.ibm.com>
>> ---
>> arch/s390/include/asm/uv.h | 1 +
>> arch/s390/kvm/interrupt.c | 53 +++++++++++++++++++++++++++++++++-----
>> arch/s390/kvm/kvm-s390.c | 12 ++++++---
>> arch/s390/kvm/kvm-s390.h | 11 ++++++++
>> 4 files changed, 68 insertions(+), 9 deletions(-)
>>
>> diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
>> index 86218382d29c..a2d376b8bce3 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 db933c252dbc..d45e26e31d3d 100644
>> --- a/arch/s390/kvm/interrupt.c
>> +++ b/arch/s390/kvm/interrupt.c
>> @@ -1901,13 +1901,12 @@ 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) {
>> VM_EVENT(kvm, 4, "%s isc %1u", "inject: I/O (AI/gisa)", isc);
>> gisa_set_ipm_gisc(gi->origin, isc);
>> kfree(inti);
>> @@ -3171,9 +3170,32 @@ 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;
>> + unsigned long 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);
>
> The gisa is a per VM structure so this value could be cached outside the
> loop. Also I'd expect that we would need to do the != 0 check only once,
> no?
Will do in front of the vcpu loop-
>
>> + 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);
>> + }
>> +}
>> +
>> +
>
> One \n too much
yep
>
>> 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;
>> @@ -3184,6 +3206,25 @@ 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;
>> + unsigned long 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 577f1ead6a51..72a3c9a7c9dd 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -2194,6 +2194,9 @@ static int kvm_s390_cpus_from_pv(struct kvm
>> *kvm, u16 *rcp, u16 *rrcp)
>> }
>> mutex_unlock(&vcpu->mutex);
>> }
>> + /* Finally enable the GISA if required for traditional KVM guests */
>
> Ensure that we re-enable gisa if the non-PV guest used it but the PV
> guest did not.
I will change the comment if that makes it more clear.
>
>> + if (use_gisa)
>> + kvm_s390_gisa_enable(kvm);
>> return ret;
>> }
>> @@ -2205,6 +2208,10 @@ static int kvm_s390_cpus_to_pv(struct kvm *kvm,
>> u16 *rc, u16 *rrc)
>> struct kvm_vcpu *vcpu;
>> + /* First disable the GISA if the ultravisor does not support AIV. */
>
> I think we should drop the "First" here.
ok
>
>> + if (!test_bit_inv(BIT_UV_FEAT_AIV, &uv_info.uv_feature_indications))
>> + kvm_s390_gisa_disable(kvm);
>> +
>> kvm_for_each_vcpu(i, vcpu, kvm) {
>> mutex_lock(&vcpu->mutex);
>> r = kvm_s390_pv_create_cpu(vcpu, rc, rrc);
>> @@ -2268,6 +2275,7 @@ static int kvm_s390_handle_pv(struct kvm *kvm,
>> struct kvm_pv_cmd *cmd)
>> */
>> if (r)
>> break;
>> +
>
> Stray whitespace change
ups
>
>> r = kvm_s390_pv_deinit_vm(kvm, &cmd->rc, &cmd->rrc);
>> /* no need to block service interrupts any more */
>> @@ -3263,9 +3271,7 @@ 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);
>
> I like that way of handling the gisa setup of VCPUs
Thanks a lot Janosch, for providing review feedback on this item.
Michael
>
>> 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 098831e815e6..4ba8fc30d87a 100644
>> --- a/arch/s390/kvm/kvm-s390.h
>> +++ b/arch/s390/kvm/kvm-s390.h
>> @@ -231,6 +231,15 @@ static inline unsigned long
>> kvm_s390_get_gfn_end(struct kvm_memslots *slots)
>> return ms->base_gfn + ms->npages;
>> }
>> +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);
>> @@ -450,6 +459,8 @@ 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);
>
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