[RFC PATCH v2 13/28] KVM: arm64: Extract & share ipa size shift calculation

Steffen Eiden
2026-04-28T16:06:27Z

Extract the ipa shift calculation from kvm_init_ipa_range into its own
function kvm_vm_type_ipa_size_shift to be shared across architectures.

User space passes a type parameter to the VM creation ioctl, indicating
the physical size of the VM. Therefore extract the ipa shift calculation
from kvm_init_ipa_range into its own function kvm_vm_type_ipa_size_shift,
so all implementers of arm64 KVM can make use of it for VM creation.

Co-developed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Signed-off-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Signed-off-by: Steffen Eiden <seiden@linux.ibm.com>
---
arch/arm64/kvm/mmu.c | 19 ++++++-------------
include/kvm/arm64/kvm_host.h | 1 +
virt/kvm/arm64/arm.c | 21 +++++++++++++++++++++
3 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
index e19ff77b3cd5..bec52291bc0c 100644
--- a/arch/arm64/kvm/mmu.c
+++ b/arch/arm64/kvm/mmu.c
@@ -874,27 +874,20 @@ static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = {

static int kvm_init_ipa_range(struct kvm_s2_mmu *mmu, unsigned long type)
{
- u32 kvm_ipa_limit = get_kvm_ipa_limit();
u64 mmfr0, mmfr1;
u32 phys_shift;
+ int r;

if (type & ~KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
return -EINVAL;

- phys_shift = KVM_VM_TYPE_ARM_IPA_SIZE(type);
if (is_protected_kvm_enabled()) {
- phys_shift = kvm_ipa_limit;
- } else if (phys_shift) {
- if (phys_shift > kvm_ipa_limit ||
- phys_shift < ARM64_MIN_PARANGE_BITS)
- return -EINVAL;
+ phys_shift = get_kvm_ipa_limit();
} else {
- phys_shift = KVM_PHYS_SHIFT;
- if (phys_shift > kvm_ipa_limit) {
- pr_warn_once("%s using unsupported default IPA limit, upgrade your VMM\n",
- current->comm);
- return -EINVAL;
- }
+ r = kvm_vm_type_ipa_size_shift(type);
+ if (r < 0)
+ return r;
+ phys_shift = r;
}

mmfr0 = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
diff --git a/include/kvm/arm64/kvm_host.h b/include/kvm/arm64/kvm_host.h
index d36ebea4d60f..8bf399508757 100644
--- a/include/kvm/arm64/kvm_host.h
+++ b/include/kvm/arm64/kvm_host.h
@@ -33,6 +33,7 @@ int kvm_vcpu_init_check_features(struct kvm_vcpu *vcpu,
const struct kvm_vcpu_init *init);
bool kvm_vcpu_init_changed(struct kvm_vcpu *vcpu,
const struct kvm_vcpu_init *init);
+int kvm_vm_type_ipa_size_shift(unsigned long type);

/* MMIO helpers */
void kvm_mmio_write_buf(void *buf, unsigned int len, unsigned long data);
diff --git a/virt/kvm/arm64/arm.c b/virt/kvm/arm64/arm.c
index b47adef65e5f..0bbfbe63e558 100644
--- a/virt/kvm/arm64/arm.c
+++ b/virt/kvm/arm64/arm.c
@@ -52,3 +52,24 @@ bool kvm_vcpu_init_changed(struct kvm_vcpu *vcpu,
return !bitmap_equal(vcpu->kvm->arch.vcpu_features, &features,
KVM_VCPU_MAX_FEATURES);
}
+
+int kvm_vm_type_ipa_size_shift(unsigned long type)
+{
+ int phys_shift;
+
+ phys_shift = KVM_VM_TYPE_ARM_IPA_SIZE(type);
+ if (phys_shift) {
+ if (phys_shift > get_kvm_ipa_limit() ||
+ phys_shift < ARM64_MIN_PARANGE_BITS)
+ return -EINVAL;
+ } else {
+ phys_shift = KVM_PHYS_SHIFT;
+ if (phys_shift > get_kvm_ipa_limit()) {
+ pr_warn_once("%s using unsupported default IPA limit, upgrade your VMM\n",
+ current->comm);
+ return -EINVAL;
+ }
+ }
+
+ return phys_shift;
+}
--
2.51.0