Commit 3e0209bb authored by Thomas Huth's avatar Thomas Huth Committed by Cornelia Huck
Browse files

hw/s390x: Add a more verbose comment about get_machine_class() and the wrappers 



While working on the "Enable adapter interruption suppression again"
recently, I had to discover that the meaning of get_machine_class()
and the related *_allowed() wrappers is not very obvious. Add a more
verbose comment here to clarify how these should be used.

Signed-off-by: default avatarThomas Huth <thuth@redhat.com>
Message-Id: <20200123170256.12386-1-thuth@redhat.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Signed-off-by: default avatarCornelia Huck <cohuck@redhat.com>
parent a2fb6b00

hw/s390x/s390-virtio-ccw.c

+13 −3
Original line number Diff line number Diff line
@@ -505,6 +505,19 @@ static inline void machine_set_dea_key_wrap(Object *obj, bool value, 


static S390CcwMachineClass *current_mc;



/*

 * Get the class of the s390-ccw-virtio machine that is currently in use.

 * Note: libvirt is using the "none" machine to probe for the features of the

 * host CPU, so in case this is called with the "none" machine, the function

 * returns the TYPE_S390_CCW_MACHINE base class. In this base class, all the

 * various "*_allowed" variables are enabled, so that the *_allowed() wrappers

 * below return the correct default value for the "none" machine.

 *

 * Attention! Do *not* add additional new wrappers for CPU features (e.g. like

 * the ri_allowed() wrapper) via this mechanism anymore. CPU features should

 * be handled via the CPU models, i.e. checking with cpu_model_allowed() during

 * CPU initialization and s390_has_feat() later should be sufficient.

 */

static S390CcwMachineClass *get_machine_class(void)

{

    if (unlikely(!current_mc)) {
@@ -521,19 +534,16 @@ static S390CcwMachineClass *get_machine_class(void) 


bool ri_allowed(void)

{

    /* for "none" machine this results in true */

    return get_machine_class()->ri_allowed;

}



bool cpu_model_allowed(void)

{

    /* for "none" machine this results in true */

    return get_machine_class()->cpu_model_allowed;

}



bool hpage_1m_allowed(void)

{

    /* for "none" machine this results in true */

    return get_machine_class()->hpage_1m_allowed;

}