• Paul Mackerras's avatar
    KVM: PPC: Book3S: Allow XICS emulation to work in nested hosts using XIVE · 03f95332
    Paul Mackerras authored
    Currently, the KVM code assumes that if the host kernel is using the
    XIVE interrupt controller (the new interrupt controller that first
    appeared in POWER9 systems), then the in-kernel XICS emulation will
    use the XIVE hardware to deliver interrupts to the guest.  However,
    this only works when the host is running in hypervisor mode and has
    full access to all of the XIVE functionality.  It doesn't work in any
    nested virtualization scenario, either with PR KVM or nested-HV KVM,
    because the XICS-on-XIVE code calls directly into the native-XIVE
    routines, which are not initialized and cannot function correctly
    because they use OPAL calls, and OPAL is not available in a guest.
    
    This means that using the in-kernel XICS emulation in a nested
    hypervisor that is using XIVE as its interrupt controller will cause a
    (nested) host kernel crash.  To fix this, we change most of the places
    where the current code calls xive_enabled() to select between the
    XICS-on-XIVE emulation and the plain XICS emulation to call a new
    function, xics_on_xive(), which returns false in a guest.
    
    However, there is a further twist.  The plain XICS emulation has some
    functions which are used in real mode and access the underlying XICS
    controller (the interrupt controller of the host) directly.  In the
    case of a nested hypervisor, this means doing XICS hypercalls
    directly.  When the nested host is using XIVE as its interrupt
    controller, these hypercalls will fail.  Therefore this also adds
    checks in the places where the XICS emulation wants to access the
    underlying interrupt controller directly, and if that is XIVE, makes
    the code use the virtual mode fallback paths, which call generic
    kernel infrastructure rather than doing direct XICS access.
    Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
    Reviewed-by: default avatarCédric Le Goater <clg@kaod.org>
    Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
    03f95332
book3s_hv_rm_xics.c 23.8 KB