Re: [PATCH v6] KVM: s390: Add new reset vcpu API

[Janosch Frank <frankja@linux.ibm.com>]

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On 1/10/20 11:36 AM, Thomas Huth wrote:
> On 10/01/2020 11.19, Janosch Frank wrote:
>> The architecture states that we need to reset local IRQs for all CPU
>> resets. Because the old reset interface did not support the normal CPU
>> reset we never did that on a normal reset.
>>
>> Let's implement an interface for the missing normal and clear resets
>> and reset all local IRQs, registers and control structures as stated
>> in the architecture.
>>
>> Userspace might already reset the registers via the vcpu run struct,
>> but as we need the interface for the interrupt clearing part anyway,
>> we implement the resets fully and don't rely on userspace to reset the
>> rest.
>>
>> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
>> ---
> [...]
>> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
>> index d9e6bf3d54f0..4936f9499291 100644
>> --- a/arch/s390/kvm/kvm-s390.c
>> +++ b/arch/s390/kvm/kvm-s390.c
>> @@ -529,6 +529,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>>  	case KVM_CAP_S390_CMMA_MIGRATION:
>>  	case KVM_CAP_S390_AIS:
>>  	case KVM_CAP_S390_AIS_MIGRATION:
>> +	case KVM_CAP_S390_VCPU_RESETS:
>>  		r = 1;
>>  		break;
>>  	case KVM_CAP_S390_HPAGE_1M:
>> @@ -2844,35 +2845,6 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>>  
>>  }
>>  
>> -static void kvm_s390_vcpu_initial_reset(struct kvm_vcpu *vcpu)
>> -{
>> -	/* this equals initial cpu reset in pop, but we don't switch to ESA */
>> -	vcpu->arch.sie_block->gpsw.mask = 0UL;
>> -	vcpu->arch.sie_block->gpsw.addr = 0UL;
>> -	kvm_s390_set_prefix(vcpu, 0);
>> -	kvm_s390_set_cpu_timer(vcpu, 0);
>> -	vcpu->arch.sie_block->ckc       = 0UL;
>> -	vcpu->arch.sie_block->todpr     = 0;
>> -	memset(vcpu->arch.sie_block->gcr, 0, 16 * sizeof(__u64));
>> -	vcpu->arch.sie_block->gcr[0]  = CR0_UNUSED_56 |
>> -					CR0_INTERRUPT_KEY_SUBMASK |
>> -					CR0_MEASUREMENT_ALERT_SUBMASK;
>> -	vcpu->arch.sie_block->gcr[14] = CR14_UNUSED_32 |
>> -					CR14_UNUSED_33 |
>> -					CR14_EXTERNAL_DAMAGE_SUBMASK;
>> -	/* make sure the new fpc will be lazily loaded */
>> -	save_fpu_regs();
>> -	current->thread.fpu.fpc = 0;
>> -	vcpu->arch.sie_block->gbea = 1;
>> -	vcpu->arch.sie_block->pp = 0;
>> -	vcpu->arch.sie_block->fpf &= ~FPF_BPBC;
>> -	vcpu->arch.pfault_token = KVM_S390_PFAULT_TOKEN_INVALID;
>> -	kvm_clear_async_pf_completion_queue(vcpu);
>> -	if (!kvm_s390_user_cpu_state_ctrl(vcpu->kvm))
>> -		kvm_s390_vcpu_stop(vcpu);
>> -	kvm_s390_clear_local_irqs(vcpu);
>> -}
>> -
>>  void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
>>  {
>>  	mutex_lock(&vcpu->kvm->lock);
>> @@ -3287,10 +3259,78 @@ static int kvm_arch_vcpu_ioctl_set_one_reg(struct kvm_vcpu *vcpu,
>>  	return r;
>>  }
>>  
>> -static int kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu)
>> +static void kvm_arch_vcpu_ioctl_normal_reset(struct kvm_vcpu *vcpu)
>>  {
>> -	kvm_s390_vcpu_initial_reset(vcpu);
>> -	return 0;
>> +	vcpu->arch.sie_block->gpsw.mask = ~PSW_MASK_RI;
>> +	vcpu->arch.pfault_token = KVM_S390_PFAULT_TOKEN_INVALID;
>> +	memset(vcpu->run->s.regs.riccb, 0, sizeof(vcpu->run->s.regs.riccb));
>> +
>> +	kvm_clear_async_pf_completion_queue(vcpu);
>> +	if (!kvm_s390_user_cpu_state_ctrl(vcpu->kvm))
>> +		kvm_s390_vcpu_stop(vcpu);
>> +	kvm_s390_clear_local_irqs(vcpu);
>> +}
>> +
>> +static void kvm_arch_vcpu_ioctl_initial_reset(struct kvm_vcpu *vcpu)
>> +{
>> +	/* Initial reset is a superset of the normal reset */
>> +	kvm_arch_vcpu_ioctl_normal_reset(vcpu);
>> +
>> +	/* this equals initial cpu reset in pop, but we don't switch to ESA */
>> +	vcpu->arch.sie_block->gpsw.mask = 0UL;
>> +	vcpu->arch.sie_block->gpsw.addr = 0UL;
>> +	kvm_s390_set_prefix(vcpu, 0);
>> +	kvm_s390_set_cpu_timer(vcpu, 0);
>> +	vcpu->arch.sie_block->ckc       = 0UL;
>> +	vcpu->arch.sie_block->todpr     = 0;
>> +	memset(vcpu->arch.sie_block->gcr, 0, 16 * sizeof(__u64));
>> +	vcpu->arch.sie_block->gcr[0]  = CR0_UNUSED_56 |
>> +					CR0_INTERRUPT_KEY_SUBMASK |
>> +					CR0_MEASUREMENT_ALERT_SUBMASK;
>> +	vcpu->arch.sie_block->gcr[14] = CR14_UNUSED_32 |
>> +					CR14_UNUSED_33 |
>> +					CR14_EXTERNAL_DAMAGE_SUBMASK;
>> +	/* make sure the new fpc will be lazily loaded */
>> +	save_fpu_regs();
>> +	current->thread.fpu.fpc = 0;
>> +	vcpu->arch.sie_block->gbea = 1;
>> +	vcpu->arch.sie_block->pp = 0;
>> +	vcpu->arch.sie_block->fpf &= ~FPF_BPBC;
>> +}
>> +
>> +static void kvm_arch_vcpu_ioctl_clear_reset(struct kvm_vcpu *vcpu)
>> +{
>> +	struct kvm_sync_regs *regs = &vcpu->run->s.regs;
>> +
>> +	/* Clear reset is a superset of the initial reset */
>> +	kvm_arch_vcpu_ioctl_normal_reset(vcpu);
>> +
>> +	memset(&regs->gprs, 0, sizeof(regs->gprs));
>> +	/*
>> +	 * Will be picked up via save_fpu_regs() in the initial reset
>> +	 * fallthrough.
> 
> The word "fallthrough" now likely should be removed from the comment.
> 
> Also, I'm not an expert in this lazy-fpu stuff, but don't you rather
> have to deal with current->thread.fpu.regs here instead?

Yes, I'll need to fix that.

> 
>> +	 */
>> +	memset(&regs->vrs, 0, sizeof(regs->vrs));
>> +	memset(&regs->acrs, 0, sizeof(regs->acrs));
>> +
>> +	regs->etoken = 0;
>> +	regs->etoken_extension = 0;
>> +
>> +	memset(&regs->gscb, 0, sizeof(regs->gscb));
>> +	if (MACHINE_HAS_GS) {
>> +		preempt_disable();
>> +		__ctl_set_bit(2, 4);
>> +		if (current->thread.gs_cb) {
>> +			vcpu->arch.host_gscb = current->thread.gs_cb;
>> +			save_gs_cb(vcpu->arch.host_gscb);
>> +		}
>> +		if (vcpu->arch.gs_enabled) {
>> +			current->thread.gs_cb = (struct gs_cb *)
>> +				&vcpu->run->s.regs.gscb;
>> +			restore_gs_cb(current->thread.gs_cb);
>> +		}
>> +		preempt_enable();
>> +	}
>>  }
> 
>  Thomas
> 



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