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authorJanosch Frank <frankja@linux.ibm.com>2018-07-13 11:28:31 +0100
committerJanosch Frank <frankja@linux.ibm.com>2018-07-30 23:13:38 +0200
commita449938297e55e7e8958f8b48583f7d342da1930 (patch)
tree89157c9c2d20a171c5685f3f7b7c1fdad72122cd /arch/s390
parenta9e00d8349c98e0973c8b0d671d69e838f7b5bcc (diff)
KVM: s390: Add huge page enablement control
General KVM huge page support on s390 has to be enabled via the kvm.hpage module parameter. Either nested or hpage can be enabled, as we currently do not support vSIE for huge backed guests. Once the vSIE support is added we will either drop the parameter or enable it as default. For a guest the feature has to be enabled through the new KVM_CAP_S390_HPAGE_1M capability and the hpage module parameter. Enabling it means that cmm can't be enabled for the vm and disables pfmf and storage key interpretation. This is due to the fact that in some cases, in upcoming patches, we have to split huge pages in the guest mapping to be able to set more granular memory protection on 4k pages. These split pages have fake page tables that are not visible to the Linux memory management which subsequently will not manage its PGSTEs, while the SIE will. Disabling these features lets us manage PGSTE data in a consistent matter and solve that problem. Signed-off-by: Janosch Frank <frankja@linux.ibm.com> Reviewed-by: David Hildenbrand <david@redhat.com>
Diffstat (limited to 'arch/s390')
-rw-r--r--arch/s390/kvm/kvm-s390.c42
1 files changed, 40 insertions, 2 deletions
diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
index 662f4d8046db..f9d90337e64a 100644
--- a/arch/s390/kvm/kvm-s390.c
+++ b/arch/s390/kvm/kvm-s390.c
@@ -172,6 +172,10 @@ static int nested;
module_param(nested, int, S_IRUGO);
MODULE_PARM_DESC(nested, "Nested virtualization support");
+/* allow 1m huge page guest backing, if !nested */
+static int hpage;
+module_param(hpage, int, 0444);
+MODULE_PARM_DESC(hpage, "1m huge page backing support");
/*
* For now we handle at most 16 double words as this is what the s390 base
@@ -475,6 +479,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_S390_AIS_MIGRATION:
r = 1;
break;
+ case KVM_CAP_S390_HPAGE_1M:
+ r = 0;
+ if (hpage)
+ r = 1;
+ break;
case KVM_CAP_S390_MEM_OP:
r = MEM_OP_MAX_SIZE;
break;
@@ -678,6 +687,27 @@ static int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
VM_EVENT(kvm, 3, "ENABLE: CAP_S390_GS %s",
r ? "(not available)" : "(success)");
break;
+ case KVM_CAP_S390_HPAGE_1M:
+ mutex_lock(&kvm->lock);
+ if (kvm->created_vcpus)
+ r = -EBUSY;
+ else if (!hpage || kvm->arch.use_cmma)
+ r = -EINVAL;
+ else {
+ r = 0;
+ kvm->mm->context.allow_gmap_hpage_1m = 1;
+ /*
+ * We might have to create fake 4k page
+ * tables. To avoid that the hardware works on
+ * stale PGSTEs, we emulate these instructions.
+ */
+ kvm->arch.use_skf = 0;
+ kvm->arch.use_pfmfi = 0;
+ }
+ mutex_unlock(&kvm->lock);
+ VM_EVENT(kvm, 3, "ENABLE: CAP_S390_HPAGE %s",
+ r ? "(not available)" : "(success)");
+ break;
case KVM_CAP_S390_USER_STSI:
VM_EVENT(kvm, 3, "%s", "ENABLE: CAP_S390_USER_STSI");
kvm->arch.user_stsi = 1;
@@ -725,10 +755,13 @@ static int kvm_s390_set_mem_control(struct kvm *kvm, struct kvm_device_attr *att
if (!sclp.has_cmma)
break;
- ret = -EBUSY;
VM_EVENT(kvm, 3, "%s", "ENABLE: CMMA support");
mutex_lock(&kvm->lock);
- if (!kvm->created_vcpus) {
+ if (kvm->created_vcpus)
+ ret = -EBUSY;
+ else if (kvm->mm->context.allow_gmap_hpage_1m)
+ ret = -EINVAL;
+ else {
kvm->arch.use_cmma = 1;
/* Not compatible with cmma. */
kvm->arch.use_pfmfi = 0;
@@ -4102,6 +4135,11 @@ static int __init kvm_s390_init(void)
return -ENODEV;
}
+ if (nested && hpage) {
+ pr_info("nested (vSIE) and hpage (huge page backing) can currently not be activated concurrently");
+ return -EINVAL;
+ }
+
for (i = 0; i < 16; i++)
kvm_s390_fac_base[i] |=
S390_lowcore.stfle_fac_list[i] & nonhyp_mask(i);