Re: [PATCH v4] KVM: s390: Add new reset vcpu API

[Cornelia Huck <cohuck@redhat.com>]

On Thu,  5 Dec 2019 07:28:10 -0500
Janosch Frank <frankja@linux.ibm.com> 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. Now that we have a new interface, let's
> properly clear out local IRQs.
> 
> Also we add a ioctl for the clear reset to have all resets exposed to
> userspace. Currently the clear reset falls back to the initial reset,
> but we plan to have clear reset specific code in the future.
> 
> Signed-off-by: Janosch Frank <frankja@linux.ibm.com>
> Reviewed-by: David Hildenbrand <david@redhat.com>
> ---
>  Documentation/virt/kvm/api.txt | 48 ++++++++++++++++++++++++++++++++++
>  arch/s390/kvm/kvm-s390.c       | 14 ++++++++++
>  include/uapi/linux/kvm.h       |  5 ++++
>  3 files changed, 67 insertions(+)
> 
> diff --git a/Documentation/virt/kvm/api.txt b/Documentation/virt/kvm/api.txt
> index 4833904d32a5..296e51f9df70 100644
> --- a/Documentation/virt/kvm/api.txt
> +++ b/Documentation/virt/kvm/api.txt
> @@ -4126,6 +4126,47 @@ Valid values for 'action':
>  #define KVM_PMU_EVENT_ALLOW 0
>  #define KVM_PMU_EVENT_DENY 1
>  
> +4.121 KVM_S390_NORMAL_RESET
> +
> +Capability: KVM_CAP_S390_VCPU_RESETS
> +Architectures: s390
> +Type: vcpu ioctl
> +Parameters: none
> +Returns: 0
> +
> +This ioctl resets VCPU registers and control structures that userspace
> +can't access via the kvm_run structure. It is intended to be called
> +when a normal reset is performed on the vcpu and clears local
> +interrupts, the riccb and PSW bit 24.
> +
> +4.122 KVM_S390_INITIAL_RESET
> +
> +Capability: none
> +Architectures: s390
> +Type: vcpu ioctl
> +Parameters: none
> +Returns: 0
> +
> +This ioctl resets VCPU registers and control structures that userspace
> +can't access via the kvm_run structure. It is intended to be called
> +when an initial reset (which is a superset of the normal reset) is
> +performed on the vcpu and additionally clears the psw, prefix, timing
> +related registers, as well as setting the control registers to their
> +initial value.
> +
> +4.123 KVM_S390_CLEAR_RESET
> +
> +Capability: KVM_CAP_S390_VCPU_RESETS
> +Architectures: s390
> +Type: vcpu ioctl
> +Parameters: none
> +Returns: 0
> +
> +This ioctl resets VCPU registers and control structures that userspace
> +can't access via the kvm_run structure. It is intended to be called
> +when an initial reset (which is a superset of the normal reset) is

s/initial/clear/
s/normal/initial/

(no need to respin, just fix up while applying :)

> +performed on the vcpu and additionally clears general, access,
> +floating and vector registers.
>  
>  5. The kvm_run structure
>  ------------------------
> @@ -5322,3 +5363,10 @@ handling by KVM (as some KVM hypercall may be mistakenly treated as TLB
>  flush hypercalls by Hyper-V) so userspace should disable KVM identification
>  in CPUID and only exposes Hyper-V identification. In this case, guest
>  thinks it's running on Hyper-V and only use Hyper-V hypercalls.
> +
> +8.22 KVM_CAP_S390_VCPU_RESETS
> +
> +Architectures: s390
> +
> +This capability indicates that the KVM_S390_NORMAL_RESET and
> +KVM_S390_CLEAR_RESET ioctls are available.

Reviewed-by: Cornelia Huck <cohuck@redhat.com>