[PATCH v13 24/48] arm64: RMI: Allow populating initial contents

Steven Price
2026-03-18T15:55:53Z

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.

Signed-off-by: Steven Price <steven.price@arm.com>
---
Changes since v12:
* The ioctl now updates the structure with the amount populated rather
than returning this through the ioctl return code.
* Use the new RMM v2.0 range based RMI calls.
* Adapt to upstream changes in kvm_gmem_populate().
Changes since v11:
* The multiplex CAP is gone and there's a new ioctl which makes use of
the generic kvm_gmem_populate() functionality.
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/include/asm/kvm_rmi.h | 4 ++
arch/arm64/kvm/Kconfig | 1 +
arch/arm64/kvm/arm.c | 13 ++++
arch/arm64/kvm/rmi.c | 111 +++++++++++++++++++++++++++++++
4 files changed, 129 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_rmi.h b/arch/arm64/include/asm/kvm_rmi.h
index 46b0cbe6c202..bf663bb240c4 100644
--- a/arch/arm64/include/asm/kvm_rmi.h
+++ b/arch/arm64/include/asm/kvm_rmi.h
@@ -96,6 +96,10 @@ int kvm_rec_enter(struct kvm_vcpu *vcpu);
int kvm_rec_pre_enter(struct kvm_vcpu *vcpu);
int handle_rec_exit(struct kvm_vcpu *vcpu, int rec_run_status);

+struct kvm_arm_rmi_populate;
+
+int kvm_arm_rmi_populate(struct kvm *kvm,
+ struct kvm_arm_rmi_populate *arg);
void kvm_realm_unmap_range(struct kvm *kvm,
unsigned long ipa,
unsigned long size,
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 1cac6dfc0972..b495dfd3a8b4 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -39,6 +39,7 @@ menuconfig KVM
select GUEST_PERF_EVENTS if PERF_EVENTS
select KVM_GUEST_MEMFD
select KVM_GENERIC_MEMORY_ATTRIBUTES
+ select HAVE_KVM_ARCH_GMEM_POPULATE
help
Support hosting virtualized guest machines.

diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index badb94b398bc..43d05da7e694 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -2089,6 +2089,19 @@ int kvm_arch_vm_ioctl(struct file *filp, unsigned int ioctl, unsigned long arg)
return -EFAULT;
return kvm_vm_ioctl_get_reg_writable_masks(kvm, &range);
}
+ case KVM_ARM_RMI_POPULATE: {
+ struct kvm_arm_rmi_populate req;
+ int ret;
+
+ if (!kvm_is_realm(kvm))
+ return -ENXIO;
+ if (copy_from_user(&req, argp, sizeof(req)))
+ return -EFAULT;
+ ret = kvm_arm_rmi_populate(kvm, &req);
+ if (copy_to_user(argp, &req, sizeof(req)))
+ return -EFAULT;
+ return ret;
+ }
default:
return -EINVAL;
}
diff --git a/arch/arm64/kvm/rmi.c b/arch/arm64/kvm/rmi.c
index 13eed6f0b9eb..b48f4e12e4e0 100644
--- a/arch/arm64/kvm/rmi.c
+++ b/arch/arm64/kvm/rmi.c
@@ -718,6 +718,80 @@ 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_page(struct kvm *kvm,
+ unsigned long ipa,
+ kvm_pfn_t dst_pfn,
+ kvm_pfn_t src_pfn,
+ unsigned long flags)
+{
+ struct realm *realm = &kvm->arch.realm;
+ phys_addr_t rd = virt_to_phys(realm->rd);
+ phys_addr_t dst_phys, src_phys;
+ int ret;
+
+ dst_phys = __pfn_to_phys(dst_pfn);
+ src_phys = __pfn_to_phys(src_pfn);
+
+ if (delegate_page(dst_phys))
+ return -ENXIO;
+
+ ret = rmi_rtt_data_map_init(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);
+
+ KVM_BUG_ON(level == RMM_RTT_MAX_LEVEL, kvm);
+
+ ret = realm_create_rtt_levels(realm, ipa, level,
+ RMM_RTT_MAX_LEVEL, NULL);
+ if (!ret) {
+ ret = rmi_rtt_data_map_init(rd, dst_phys, ipa, src_phys,
+ flags);
+ }
+ }
+
+ if (ret) {
+ if (WARN_ON(undelegate_page(dst_phys))) {
+ /* Undelegate failed, so we leak the page */
+ get_page(pfn_to_page(dst_pfn));
+ }
+ }
+
+ return ret;
+}
+
+static int populate_region_cb(struct kvm *kvm, gfn_t gfn, kvm_pfn_t pfn,
+ struct page *src_page, void *opaque)
+{
+ unsigned long data_flags = *(unsigned long *)opaque;
+ phys_addr_t ipa = gfn_to_gpa(gfn);
+
+ if (!src_page)
+ return -EOPNOTSUPP;
+
+ return realm_create_protected_data_page(kvm, ipa, pfn,
+ page_to_pfn(src_page),
+ data_flags);
+}
+
+static long populate_region(struct kvm *kvm,
+ gfn_t base_gfn,
+ unsigned long pages,
+ u64 uaddr,
+ unsigned long data_flags)
+{
+ long ret = 0;
+
+ mutex_lock(&kvm->slots_lock);
+ mmap_read_lock(current->mm);
+ ret = kvm_gmem_populate(kvm, base_gfn, u64_to_user_ptr(uaddr), pages,
+ populate_region_cb, &data_flags);
+ mmap_read_unlock(current->mm);
+ mutex_unlock(&kvm->slots_lock);
+
+ return ret;
+}
+
enum ripas_action {
RIPAS_INIT,
RIPAS_SET,
@@ -815,6 +889,43 @@ static int realm_ensure_created(struct kvm *kvm)
return -ENXIO;
}

+int kvm_arm_rmi_populate(struct kvm *kvm,
+ struct kvm_arm_rmi_populate *args)
+{
+ unsigned long data_flags = 0;
+ unsigned long ipa_start = args->base;
+ unsigned long ipa_end = ipa_start + args->size;
+ long pages_populated;
+ int ret;
+
+ if (args->reserved ||
+ (args->flags & ~KVM_ARM_RMI_POPULATE_FLAGS_MEASURE) ||
+ !IS_ALIGNED(ipa_start, PAGE_SIZE) ||
+ !IS_ALIGNED(ipa_end, PAGE_SIZE) ||
+ !IS_ALIGNED(args->source_uaddr, PAGE_SIZE))
+ return -EINVAL;
+
+ ret = realm_ensure_created(kvm);
+ if (ret)
+ return ret;
+
+ if (args->flags & KVM_ARM_RMI_POPULATE_FLAGS_MEASURE)
+ data_flags |= RMI_MEASURE_CONTENT;
+
+ pages_populated = populate_region(kvm, gpa_to_gfn(ipa_start),
+ args->size >> PAGE_SHIFT,
+ args->source_uaddr, data_flags);
+
+ if (pages_populated < 0)
+ return pages_populated;
+
+ args->size -= pages_populated << PAGE_SHIFT;
+ args->source_uaddr += pages_populated << PAGE_SHIFT;
+ args->base += pages_populated << PAGE_SHIFT;
+
+ return 0;
+}
+
static void kvm_complete_ripas_change(struct kvm_vcpu *vcpu)
{
struct kvm *kvm = vcpu->kvm;
--
2.43.0