• Nicholas Piggin's avatar
    powerpc/pseries: Add KVM guest doorbell restrictions · 107c5500
    Nicholas Piggin authored
    KVM guests have certain restrictions and performance quirks when using
    doorbells. This patch moves the EPAPR KVM guest test so it can be shared
    with PSERIES, and uses that in doorbell setup code to apply the KVM
    guest quirks and  improves IPI performance for two cases:
    
     - PowerVM guests may now use doorbells even if they are secure.
    
     - KVM guests no longer use doorbells if XIVE is available.
    
    There is a valid complaint that "KVM guest" is not a very reasonable
    thing to test for, it's preferable for the hypervisor to advertise
    particular behaviours to the guest so they could change if the
    hypervisor implementation or configuration changes. However in this case
    we were already assuming a KVM guest worst case, so this patch is about
    containing those quirks. If KVM later advertises fast doorbells, we
    should test for that and override the quirks.
    Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
    Tested-by: default avatarCédric Le Goater <clg@kaod.org>
    Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
    Link: https://lore.kernel.org/r/20200726035155.1424103-4-npiggin@gmail.com
    107c5500
Makefile 6.07 KB