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

Pierre Morel
2022-01-24T14:23:10Z

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