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    SubjectRe: [PATCH v2 00/30] KVM: s390: enable zPCI for interpretive execution
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    On 1/14/22 21:31, 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.

    I did the comment in a patch but I think that centralizing it here is
    clearer: I think having a documentation in Documentation/S390 like we
    have already for VFIO AP and VFIO CCW would be a good thing.

    --
    Pierre Morel
    IBM Lab Boeblingen

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