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KVM: s390: Add capability to support 2G hugepages

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Add KVM_CAP_S390_HPAGE_2G to signal to userspace that 2G hugepages may
be used to back the guest; restrictions apply similar to 1M hugepages.

Enable the (for now still ignored) GMAP_FLAG_ALLOW_HPAGE_2G flag for
the guest gmap, and propagate / disable it as necessary.

Reviewed-by: Steffen Eiden <seiden@linux.ibm.com>
Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
Message-ID: <20260609150930.665370-3-imbrenda@linux.ibm.com>
This commit is contained in:
Claudio Imbrenda 2026-06-09 17:09:28 +02:00
parent 782fec4ab9
commit 103ff3a50e
4 changed files with 36 additions and 1 deletions
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5
arch/s390/kvm/gmap.c
View File

@ -105,6 +105,11 @@ static void gmap_add_child(struct gmap *parent, struct gmap *child)
else
clear_bit(GMAP_FLAG_ALLOW_HPAGE_1M, &child->flags);
if (test_bit(GMAP_FLAG_ALLOW_HPAGE_2G, &parent->flags))
set_bit(GMAP_FLAG_ALLOW_HPAGE_2G, &child->flags);
else
clear_bit(GMAP_FLAG_ALLOW_HPAGE_2G, &child->flags);
if (kvm_is_ucontrol(parent->kvm))
clear_bit(GMAP_FLAG_OWNS_PAGETABLES, &child->flags);
list_add(&child->list, &parent->children);

26
arch/s390/kvm/kvm-s390.c
View File

@ -646,6 +646,11 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
if (hpage && !(kvm && kvm_is_ucontrol(kvm)))
r = 1;
break;
case KVM_CAP_S390_HPAGE_2G:
r = 0;
if (hpage_2g && !(kvm && kvm_is_ucontrol(kvm)))
r = 1;
break;
case KVM_CAP_S390_MEM_OP:
r = MEM_OP_MAX_SIZE;
break;
@ -902,6 +907,27 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
VM_EVENT(kvm, 3, "ENABLE: CAP_S390_HPAGE %s",
r ? "(not available)" : "(success)");
break;
case KVM_CAP_S390_HPAGE_2G:
mutex_lock(&kvm->lock);
if (kvm->created_vcpus) {
r = -EBUSY;
} else if (!hpage_2g || kvm->arch.use_cmma || kvm_is_ucontrol(kvm)) {
r = -EINVAL;
} else {
r = 0;
set_bit(GMAP_FLAG_ALLOW_HPAGE_2G, &kvm->arch.gmap->flags);
/*
* 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_2G %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;

5
arch/s390/kvm/pv.c
View File

@ -721,7 +721,10 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
uvcb.flags.ap_allow_instr = kvm->arch.model.uv_feat_guest.ap;
uvcb.flags.ap_instr_intr = kvm->arch.model.uv_feat_guest.ap_intr;
clear_bit(GMAP_FLAG_ALLOW_HPAGE_1M, &kvm->arch.gmap->flags);
scoped_guard(write_lock, &kvm->mmu_lock) {
clear_bit(GMAP_FLAG_ALLOW_HPAGE_1M, &kvm->arch.gmap->flags);
clear_bit(GMAP_FLAG_ALLOW_HPAGE_2G, &kvm->arch.gmap->flags);
}
gmap_split_huge_pages(kvm->arch.gmap);
cc = uv_call_sched(0, (u64)&uvcb);

1
include/uapi/linux/kvm.h
View File

@ -996,6 +996,7 @@ struct kvm_enable_cap {
#define KVM_CAP_S390_USER_OPEREXEC 246
#define KVM_CAP_S390_KEYOP 247
#define KVM_CAP_S390_VSIE_ESAMODE 248
#define KVM_CAP_S390_HPAGE_2G 249
struct kvm_irq_routing_irqchip {
__u32 irqchip;