[PATCH v1 1/3] KVM: s390: Add module parameter to fence 2G hugepages

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

Add the hpage_2g module parameter to KVM to allow enabling or disabling
2G hugepages in KVM.

If hpage_2g is enabled but hpage is not enabled, print a message and
disable hpage_2g.

Opportunistically fix the comment for the hpage module parameter.

Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
---
 arch/s390/kvm/kvm-s390.c | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index ffb20a64d328..801a622691b6 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -204,11 +204,16 @@ static int nested;
 module_param(nested, int, S_IRUGO);
 MODULE_PARM_DESC(nested, "Nested virtualization support");
 
-/* allow 1m huge page guest backing, if !nested */
+/* allow 1m huge page guest backing */
 static int hpage;
 module_param(hpage, int, 0444);
 MODULE_PARM_DESC(hpage, "1m huge page backing support");
 
+/* allow 2g huge page guest backing */
+static int hpage_2g;
+module_param(hpage_2g, int, 0444);
+MODULE_PARM_DESC(hpage_2g, "2g huge page backing support");
+
 /* maximum percentage of steal time for polling.  >100 is treated like 100 */
 static u8 halt_poll_max_steal = 10;
 module_param(halt_poll_max_steal, byte, 0644);
@@ -5820,6 +5825,11 @@ static int __init kvm_s390_init(void)
 		return -ENODEV;
 	}
 
+	if (hpage_2g && !hpage) {
+		hpage_2g = 0;
+		pr_info("Disabling 2G hugepage support, since 1M hugepage support is not enabled.\n");
+	}
+
 	for (i = 0; i < 16; i++)
 		kvm_s390_fac_base[i] |=
 			stfle_fac_list[i] & nonhyp_mask(i);
-- 
2.54.0