Re: [PATCH 19/32] KVM: s390: mechanism to enable guest zPCI Interpretation

[Christian Borntraeger <borntraeger@linux.ibm.com>]

Am 07.12.21 um 21:57 schrieb Matthew Rosato:
> 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         | 43 ++++++++++++++++++++++++++++++++
>   arch/s390/kvm/kvm-s390.h         | 10 ++++++++
>   3 files changed, 57 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 a680f2a02b67..361d742cdf0d 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -1023,6 +1023,47 @@ 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)
> +{
> +	/*
> +	 * If the facilities aren't available for PCI interpretation and
> +	 * interrupt forwarding, we shouldn't be here.
> +	 */

This reads like we want a WARN_ON or BUG_ON, but as we call this uncoditionally this is
actually a valid check. So instead of "shouldn't be here" say something like "bail out
if interpretion is not active".  ?

> +	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;
> +}
> +
> +void kvm_s390_vcpu_pci_enable_interp(struct kvm *kvm)
> +{
> +	struct kvm_vcpu *vcpu;
> +	int i;
> +
> +	/*
> +	 * If host facilities are available, turn on interpretation for the
> +	 * life of this guest
> +	 */
> +	if (!test_facility(69) || !test_facility(70) || !test_facility(71) ||
> +	    !test_facility(72))
> +		return;

Wouldnt that also enable interpretion for VSIE? I guess we should check for the
sclp facilities from patches 1,2,3, and 4 instead.


> +
> +	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;
> @@ -3288,6 +3329,8 @@ static int kvm_s390_vcpu_setup(struct kvm_vcpu *vcpu)
>   h
>   	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
>    *
>