Re: [PATCH v2 17/30] KVM: s390: mechanism to enable guest zPCI Interpretation

[Pierre Morel <pmorel@linux.ibm.com>]

On 1/14/22 21:31, Matthew Rosato wrote:
> The guest must have access to certain facilities in order to allow
> interpretive execution of zPCI instructions and adapter event
> notifications.  However, there are some cases where a guest might
> disable interpretation -- provide a mechanism via which we can defer
> enabling the associated zPCI interpretation facilities until the guest
> indicates it wishes to use them.
> 
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
>   arch/s390/include/asm/kvm_host.h |  4 ++++
>   arch/s390/kvm/kvm-s390.c         | 40 ++++++++++++++++++++++++++++++++
>   arch/s390/kvm/kvm-s390.h         | 10 ++++++++
>   3 files changed, 54 insertions(+)
> 
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index 3f147b8d050b..38982c1de413 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -252,7 +252,10 @@ struct kvm_s390_sie_block {
>   #define ECB2_IEP	0x20
>   #define ECB2_PFMFI	0x08
>   #define ECB2_ESCA	0x04
> +#define ECB2_ZPCI_LSI	0x02
>   	__u8    ecb2;                   /* 0x0062 */
> +#define ECB3_AISI	0x20
> +#define ECB3_AISII	0x10
>   #define ECB3_DEA 0x08
>   #define ECB3_AES 0x04
>   #define ECB3_RI  0x01
> @@ -938,6 +941,7 @@ struct kvm_arch{
>   	int use_cmma;
>   	int use_pfmfi;
>   	int use_skf;
> +	int use_zpci_interp;
>   	int user_cpu_state_ctrl;
>   	int user_sigp;
>   	int user_stsi;
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index ab8b56deed11..b6c32fc3b272 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -1029,6 +1029,44 @@ static int kvm_s390_vm_set_crypto(struct kvm *kvm, struct kvm_device_attr *attr)
>   	return 0;
>   }
>   
> +static void kvm_s390_vcpu_pci_setup(struct kvm_vcpu *vcpu)
> +{
> +	/* Only set the ECB bits after guest requests zPCI interpretation */
> +	if (!vcpu->kvm->arch.use_zpci_interp)
> +		return;
> +
> +	vcpu->arch.sie_block->ecb2 |= ECB2_ZPCI_LSI;
> +	vcpu->arch.sie_block->ecb3 |= ECB3_AISII + ECB3_AISI;

As far as I understood, the interpretation is only possible if a gisa 
designation is associated with the PCI function via CLP enable.

Why do we setup the SIE ECB only when the guest requests for 
interpretation and not systematically in vcpu_setup?

If ECB2_ZPCI_LSI, ECB3_AISII or ECB3_AISI have an effect when the gisa 
designation is not specified shouldn't we have a way to clear these bits?

> +}
> +
> +void kvm_s390_vcpu_pci_enable_interp(struct kvm *kvm)
> +{
> +	struct kvm_vcpu *vcpu;
> +	int i;
> +
> +	/*
> +	 * If host is configured for PCI and the necessary facilities are
> +	 * available, turn on interpretation for the life of this guest
> +	 */
> +	if (!IS_ENABLED(CONFIG_PCI) || !sclp.has_zpci_lsi || !sclp.has_aisii ||
> +	    !sclp.has_aeni || !sclp.has_aisi)
> +		return;
> +
> +	mutex_lock(&kvm->lock);
> +
> +	kvm->arch.use_zpci_interp = 1;
> +
> +	kvm_s390_vcpu_block_all(kvm);
> +
> +	kvm_for_each_vcpu(i, vcpu, kvm) {
> +		kvm_s390_vcpu_pci_setup(vcpu);
> +		kvm_s390_sync_request(KVM_REQ_VSIE_RESTART, vcpu);
> +	}
> +
> +	kvm_s390_vcpu_unblock_all(kvm);
> +	mutex_unlock(&kvm->lock);
> +}
> +
>   static void kvm_s390_sync_request_broadcast(struct kvm *kvm, int req)
>   {
>   	int cx;
> @@ -3282,6 +3320,8 @@ static int kvm_s390_vcpu_setup(struct kvm_vcpu *vcpu)
>   
>   	kvm_s390_vcpu_crypto_setup(vcpu);
>   
> +	kvm_s390_vcpu_pci_setup(vcpu);
> +
>   	mutex_lock(&vcpu->kvm->lock);
>   	if (kvm_s390_pv_is_protected(vcpu->kvm)) {
>   		rc = kvm_s390_pv_create_cpu(vcpu, &uvrc, &uvrrc);
> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
> index c07a050d757d..a2eccb8b977e 100644
> --- a/arch/s390/kvm/kvm-s390.h
> +++ b/arch/s390/kvm/kvm-s390.h
> @@ -481,6 +481,16 @@ void kvm_s390_reinject_machine_check(struct kvm_vcpu *vcpu,
>    */
>   void kvm_s390_vcpu_crypto_reset_all(struct kvm *kvm);
>   
> +/**
> + * kvm_s390_vcpu_pci_enable_interp
> + *
> + * Set the associated PCI attributes for each vcpu to allow for zPCI Load/Store
> + * interpretation as well as adapter interruption forwarding.
> + *
> + * @kvm: the KVM guest
> + */
> +void kvm_s390_vcpu_pci_enable_interp(struct kvm *kvm);
> +
>   /**
>    * diag9c_forwarding_hz
>    *
> 

-- 
Pierre Morel
IBM Lab Boeblingen