• Paul Mackerras's avatar
    KVM: PPC: Book3S HV: Simplify machine check handling · 884dfb72
    Paul Mackerras authored
    This makes the handling of machine check interrupts that occur inside
    a guest simpler and more robust, with less done in assembler code and
    in real mode.
    
    Now, when a machine check occurs inside a guest, we always get the
    machine check event struct and put a copy in the vcpu struct for the
    vcpu where the machine check occurred.  We no longer call
    machine_check_queue_event() from kvmppc_realmode_mc_power7(), because
    on POWER8, when a vcpu is running on an offline secondary thread and
    we call machine_check_queue_event(), that calls irq_work_queue(),
    which doesn't work because the CPU is offline, but instead triggers
    the WARN_ON(lazy_irq_pending()) in pnv_smp_cpu_kill_self() (which
    fires again and again because nothing clears the condition).
    
    All that machine_check_queue_event() actually does is to cause the
    event to be printed to the console.  For a machine check occurring in
    the guest, we now print the event in kvmppc_handle_exit_hv()
    instead.
    
    The assembly code at label machine_check_realmode now just calls C
    code and then continues exiting the guest.  We no longer either
    synthesize a machine check for the guest in assembly code or return
    to the guest without a machine check.
    
    The code in kvmppc_handle_exit_hv() is extended to handle the case
    where the guest is not FWNMI-capable.  In that case we now always
    synthesize a machine check interrupt for the guest.  Previously, if
    the host thinks it has recovered the machine check fully, it would
    return to the guest without any notification that the machine check
    had occurred.  If the machine check was caused by some action of the
    guest (such as creating duplicate SLB entries), it is much better to
    tell the guest that it has caused a problem.  Therefore we now always
    generate a machine check interrupt for guests that are not
    FWNMI-capable.
    Reviewed-by: default avatarAravinda Prasad <aravinda@linux.vnet.ibm.com>
    Reviewed-by: default avatarMahesh Salgaonkar <mahesh@linux.vnet.ibm.com>
    Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    884dfb72
book3s.c 27.1 KB