Commit 28221f9c authored by Janosch Frank's avatar Janosch Frank Committed by Cornelia Huck
Browse files

s390x: Fence huge pages prior to 3.1 



As the kernel has no way of disallowing the start of a huge page
backed VM, we can migrate a running huge backed VM to a host that has
no huge page KVM support.

Let's glue huge page support support to the 3.1 machine, so we do not
migrate to a destination host that doesn't have QEMU huge page support
and can stop migration if KVM doesn't indicate support.

Signed-off-by: default avatarJanosch Frank <frankja@linux.ibm.com>
Message-Id: <20180928093435.198573-1-frankja@linux.ibm.com>
Reviewed-by: default avatarDavid Hildenbrand <david@redhat.com>
Signed-off-by: default avatarCornelia Huck <cohuck@redhat.com>
parent cb89b349

hw/s390x/s390-virtio-ccw.c

+10 −0
Original line number Diff line number Diff line
@@ -456,6 +456,7 @@ static void ccw_machine_class_init(ObjectClass *oc, void *data) 
    s390mc->ri_allowed = true;

    s390mc->cpu_model_allowed = true;

    s390mc->css_migration_enabled = true;

    s390mc->hpage_1m_allowed = true;

    mc->init = ccw_init;

    mc->reset = s390_machine_reset;

    mc->hot_add_cpu = s390_hot_add_cpu;
@@ -535,6 +536,12 @@ bool cpu_model_allowed(void) 
    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;

}



static char *machine_get_loadparm(Object *obj, Error **errp)

{

    S390CcwMachineState *ms = S390_CCW_MACHINE(obj);
@@ -747,6 +754,9 @@ static void ccw_machine_3_0_instance_options(MachineState *machine) 


static void ccw_machine_3_0_class_options(MachineClass *mc)

{

    S390CcwMachineClass *s390mc = S390_MACHINE_CLASS(mc);



    s390mc->hpage_1m_allowed = false;

    ccw_machine_3_1_class_options(mc);

    SET_MACHINE_COMPAT(mc, CCW_COMPAT_3_0);

}

include/hw/s390x/s390-virtio-ccw.h

+3 −0
Original line number Diff line number Diff line
@@ -39,12 +39,15 @@ typedef struct S390CcwMachineClass { 
    bool ri_allowed;

    bool cpu_model_allowed;

    bool css_migration_enabled;

    bool hpage_1m_allowed;

} S390CcwMachineClass;



/* runtime-instrumentation allowed by the machine */

bool ri_allowed(void);

/* cpu model allowed by the machine */

bool cpu_model_allowed(void);

/* 1M huge page mappings allowed by the machine */

bool hpage_1m_allowed(void);



/**

 * Returns true if (vmstate based) migration of the channel subsystem

target/s390x/kvm.c

+6 −0
Original line number Diff line number Diff line
@@ -292,6 +292,12 @@ static int kvm_s390_configure_mempath_backing(KVMState *s) 
        return 0;

    }



    if (!hpage_1m_allowed()) {

        error_report("This QEMU machine does not support huge page "

                     "mappings");

        return -EINVAL;

    }



    if (path_psize != 1 * MiB) {

        error_report("Memory backing with 2G pages was specified, "

                     "but KVM does not support this memory backing");