• Paul Mackerras's avatar
    KVM: PPC: Book3S HV: Don't lose pending doorbell request on migration on P9 · 30fbe0d3
    Paul Mackerras authored
    commit ff42df49 upstream.
    
    On POWER9, when userspace reads the value of the DPDES register on a
    vCPU, it is possible for 0 to be returned although there is a doorbell
    interrupt pending for the vCPU.  This can lead to a doorbell interrupt
    being lost across migration.  If the guest kernel uses doorbell
    interrupts for IPIs, then it could malfunction because of the lost
    interrupt.
    
    This happens because a newly-generated doorbell interrupt is signalled
    by setting vcpu->arch.doorbell_request to 1; the DPDES value in
    vcpu->arch.vcore->dpdes is not updated, because it can only be updated
    when holding the vcpu mutex, in order to avoid races.
    
    To fix this, we OR in vcpu->arch.doorbell_request when reading the
    DPDES value.
    
    Cc: stable@vger.kernel.org # v4.13+
    Fixes: 57900694 ("KVM: PPC: Book3S HV: Virtualize doorbell facility on POWER9")
    Signed-off-by: default avatarPaul Mackerras <paulus@ozlabs.org>
    Tested-by: default avatarAlexey Kardashevskiy <aik@ozlabs.ru>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
    30fbe0d3
book3s_hv.c 119 KB