[PATCH v10 19/43] arm64: RME: Allow populating initial contents

Steven Price
2025-08-20T14:58:47Z

The VMM needs to populate the realm with some data before starting (e.g.
a kernel and initrd). This is measured by the RMM and used as part of
the attestation later on.

Co-developed-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Steven Price <steven.price@arm.com>
Reviewed-by: Gavin Shan <gshan@redhat.com>
---
Changes since v7:
* Improve the error codes.
* Other minor changes from review.
Changes since v6:
* Handle host potentially having a larger page size than the RMM
granule.
* Drop historic "par" (protected address range) from
populate_par_region() - it doesn't exist within the current
architecture.
* Add a cond_resched() call in kvm_populate_realm().
Changes since v5:
* Refactor to use PFNs rather than tracking struct page in
realm_create_protected_data_page().
* Pull changes from a later patch (in the v5 series) for accessing
pages from a guest memfd.
* Do the populate in chunks to avoid holding locks for too long and
triggering RCU stall warnings.
---
arch/arm64/kvm/rme.c | 227 +++++++++++++++++++++++++++++++++++++++++++
1 file changed, 227 insertions(+)

diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
index 22168e8d8db7..817eb5c96728 100644
--- a/arch/arm64/kvm/rme.c
+++ b/arch/arm64/kvm/rme.c
@@ -663,6 +663,221 @@ void kvm_realm_unmap_range(struct kvm *kvm, unsigned long start,
realm_unmap_private_range(kvm, start, end, may_block);
}

+static int realm_create_protected_data_granule(struct realm *realm,
+ unsigned long ipa,
+ phys_addr_t dst_phys,
+ phys_addr_t src_phys,
+ unsigned long flags)
+{
+ phys_addr_t rd = virt_to_phys(realm->rd);
+ int ret;
+
+ if (rmi_granule_delegate(dst_phys))
+ return -ENXIO;
+
+ ret = rmi_data_create(rd, dst_phys, ipa, src_phys, flags);
+ if (RMI_RETURN_STATUS(ret) == RMI_ERROR_RTT) {
+ /* Create missing RTTs and retry */
+ int level = RMI_RETURN_INDEX(ret);
+
+ WARN_ON(level == RMM_RTT_MAX_LEVEL);
+
+ ret = realm_create_rtt_levels(realm, ipa, level,
+ RMM_RTT_MAX_LEVEL, NULL);
+ if (ret)
+ return -EIO;
+
+ ret = rmi_data_create(rd, dst_phys, ipa, src_phys, flags);
+ }
+ if (ret)
+ return -EIO;
+
+ return 0;
+}
+
+static int realm_create_protected_data_page(struct realm *realm,
+ unsigned long ipa,
+ kvm_pfn_t dst_pfn,
+ kvm_pfn_t src_pfn,
+ unsigned long flags)
+{
+ unsigned long rd = virt_to_phys(realm->rd);
+ phys_addr_t dst_phys, src_phys;
+ bool undelegate_failed = false;
+ int ret, offset;
+
+ dst_phys = __pfn_to_phys(dst_pfn);
+ src_phys = __pfn_to_phys(src_pfn);
+
+ for (offset = 0; offset < PAGE_SIZE; offset += RMM_PAGE_SIZE) {
+ ret = realm_create_protected_data_granule(realm,
+ ipa,
+ dst_phys,
+ src_phys,
+ flags);
+ if (ret)
+ goto err;
+
+ ipa += RMM_PAGE_SIZE;
+ dst_phys += RMM_PAGE_SIZE;
+ src_phys += RMM_PAGE_SIZE;
+ }
+
+ return 0;
+
+err:
+ if (ret == -EIO) {
+ /* current offset needs undelegating */
+ if (WARN_ON(rmi_granule_undelegate(dst_phys)))
+ undelegate_failed = true;
+ }
+ while (offset > 0) {
+ ipa -= RMM_PAGE_SIZE;
+ offset -= RMM_PAGE_SIZE;
+ dst_phys -= RMM_PAGE_SIZE;
+
+ rmi_data_destroy(rd, ipa, NULL, NULL);
+
+ if (WARN_ON(rmi_granule_undelegate(dst_phys)))
+ undelegate_failed = true;
+ }
+
+ if (undelegate_failed) {
+ /*
+ * A granule could not be undelegated,
+ * so the page has to be leaked
+ */
+ get_page(pfn_to_page(dst_pfn));
+ }
+
+ return -ENXIO;
+}
+
+static int populate_region(struct kvm *kvm,
+ phys_addr_t ipa_base,
+ phys_addr_t ipa_end,
+ unsigned long data_flags)
+{
+ struct realm *realm = &kvm->arch.realm;
+ struct kvm_memory_slot *memslot;
+ gfn_t base_gfn, end_gfn;
+ int idx;
+ phys_addr_t ipa = ipa_base;
+ int ret = 0;
+
+ base_gfn = gpa_to_gfn(ipa_base);
+ end_gfn = gpa_to_gfn(ipa_end);
+
+ idx = srcu_read_lock(&kvm->srcu);
+ memslot = gfn_to_memslot(kvm, base_gfn);
+ if (!memslot) {
+ ret = -EFAULT;
+ goto out;
+ }
+
+ /* We require the region to be contained within a single memslot */
+ if (memslot->base_gfn + memslot->npages < end_gfn) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ if (!kvm_slot_can_be_private(memslot)) {
+ ret = -EPERM;
+ goto out;
+ }
+
+ while (ipa < ipa_end) {
+ struct vm_area_struct *vma;
+ unsigned long hva;
+ struct page *page;
+ bool writeable;
+ kvm_pfn_t pfn;
+ kvm_pfn_t priv_pfn;
+ struct page *gmem_page;
+
+ hva = gfn_to_hva_memslot(memslot, gpa_to_gfn(ipa));
+ vma = vma_lookup(current->mm, hva);
+ if (!vma) {
+ ret = -EFAULT;
+ break;
+ }
+
+ pfn = __kvm_faultin_pfn(memslot, gpa_to_gfn(ipa), FOLL_WRITE,
+ &writeable, &page);
+
+ if (is_error_pfn(pfn)) {
+ ret = -EFAULT;
+ break;
+ }
+
+ ret = kvm_gmem_get_pfn(kvm, memslot,
+ ipa >> PAGE_SHIFT,
+ &priv_pfn, &gmem_page, NULL);
+ if (ret)
+ break;
+
+ ret = realm_create_protected_data_page(realm, ipa,
+ priv_pfn,
+ pfn,
+ data_flags);
+
+ kvm_release_page_clean(page);
+
+ if (ret)
+ break;
+
+ ipa += PAGE_SIZE;
+ }
+
+out:
+ srcu_read_unlock(&kvm->srcu, idx);
+ return ret;
+}
+
+static int kvm_populate_realm(struct kvm *kvm,
+ struct arm_rme_populate_realm *args)
+{
+ phys_addr_t ipa_base, ipa_end;
+ unsigned long data_flags = 0;
+
+ if (kvm_realm_state(kvm) != REALM_STATE_NEW)
+ return -EPERM;
+
+ if (!IS_ALIGNED(args->base, PAGE_SIZE) ||
+ !IS_ALIGNED(args->size, PAGE_SIZE) ||
+ (args->flags & ~RMI_MEASURE_CONTENT))
+ return -EINVAL;
+
+ ipa_base = args->base;
+ ipa_end = ipa_base + args->size;
+
+ if (ipa_end < ipa_base)
+ return -EINVAL;
+
+ if (args->flags & RMI_MEASURE_CONTENT)
+ data_flags |= RMI_MEASURE_CONTENT;
+
+ /*
+ * Perform the population in parts to ensure locks are not held for too
+ * long
+ */
+ while (ipa_base < ipa_end) {
+ phys_addr_t end = min(ipa_end, ipa_base + SZ_2M);
+
+ int ret = populate_region(kvm, ipa_base, end,
+ args->flags);
+
+ if (ret)
+ return ret;
+
+ ipa_base = end;
+
+ cond_resched();
+ }
+
+ return 0;
+}
+
enum ripas_action {
RIPAS_INIT,
RIPAS_SET,
@@ -907,6 +1122,18 @@ int kvm_realm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
r = kvm_init_ipa_range_realm(kvm, &args);
break;
}
+ case KVM_CAP_ARM_RME_POPULATE_REALM: {
+ struct arm_rme_populate_realm args;
+ void __user *argp = u64_to_user_ptr(cap->args[1]);
+
+ if (copy_from_user(&args, argp, sizeof(args))) {
+ r = -EFAULT;
+ break;
+ }
+
+ r = kvm_populate_realm(kvm, &args);
+ break;
+ }
default:
r = -EINVAL;
break;
--
2.43.0