Re: [PATCH v2 00/30] KVM: s390: enable zPCI for interpretive execution

Matthew Rosato
2022-01-14T20:49:53Z

On 1/14/22 3:31 PM, Matthew Rosato wrote:
> Enable interpretive execution of zPCI instructions + adapter interruption
> forwarding for s390x KVM vfio-pci. This is done by introducing a series
> of new vfio-pci feature ioctls that are unique vfio-pci-zdev (s390x) and
> are used to negotiate the various aspects of zPCI interpretation setup.
> By allowing intepretation of zPCI instructions and firmware delivery of
> interrupts to guests, we can significantly reduce the frequency of guest
> SIE exits for zPCI. We then see additional gains by handling a hot-path
> instruction that can still intercept to the hypervisor (RPCIT) directly
> in kvm.
>
> From the perspective of guest configuration, you passthrough zPCI devices
> in the same manner as before, with intepretation support being used by
> default if available in kernel+qemu.
>
> Will reply with a link to the associated QEMU series.