Re: [PATCH v7 14/22] KVM: s390: mechanism to enable guest zPCI Interpretation

Thomas Huth
2022-05-16T10:49:37Z

On 13/05/2022 21.15, 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.
>
> Reviewed-by: Christian Borntraeger <borntraeger@linux.ibm.com>
> Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
> Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
> ---
> arch/s390/include/asm/kvm_host.h | 4 ++++
> arch/s390/kvm/kvm-s390.c | 38 ++++++++++++++++++++++++++++++++
> arch/s390/kvm/kvm-s390.h | 10 +++++++++
> 3 files changed, 52 insertions(+)
>
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index c1518a505060..8e381603b6a7 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -254,7 +254,10 @@ 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
> @@ -940,6 +943,7 @@ 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 5a0fbfd19c4a..0797661732cc 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -1031,6 +1031,42 @@ 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;
> +}
> +
> +void kvm_s390_vcpu_pci_enable_interp(struct kvm *kvm)
> +{
> + struct kvm_vcpu *vcpu;
> + unsigned long i;
> +
> + lockdep_assert_held(&kvm->lock);
> +
> + /*
> + * If host is configured for PCI and the necessary facilities are
> + * available, turn on interpretation for the life of this guest
> + */

I'd suggest to move the comment after the if-statement - it seems to fit
better there.

> + if (!kvm_s390_pci_interp_allowed())
> + return;
> +
> + 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);
> +}

Thomas