Re: [PATCH v2 20/43] arm64: RME: Allow populating initial contents

Suzuki K Poulose
2024-04-19T13:17:37Z

On 12/04/2024 09:42, Steven Price wrote:
> 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>
> ---
> arch/arm64/kvm/rme.c | 234 +++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 234 insertions(+)
>
> diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
> index 0a3f823b2446..4aab507f896e 100644
> --- a/arch/arm64/kvm/rme.c
> +++ b/arch/arm64/kvm/rme.c
> @@ -4,6 +4,7 @@
> */
>
> #include <linux/kvm_host.h>
> +#include <linux/hugetlb.h>
>
> #include <asm/kvm_emulate.h>
> #include <asm/kvm_mmu.h>
> @@ -547,6 +548,227 @@ void kvm_realm_unmap_range(struct kvm *kvm, unsigned long ipa, u64 size,
> realm_fold_rtt_range(realm, ipa, end);
> }
>
> +static int realm_create_protected_data_page(struct realm *realm,
> + unsigned long ipa,
> + struct page *dst_page,
> + struct page *src_page,
> + unsigned long flags)
> +{
> + phys_addr_t dst_phys, src_phys;
> + int ret;
> +
> + dst_phys = page_to_phys(dst_page);
> + src_phys = page_to_phys(src_page);
> +
> + if (rmi_granule_delegate(dst_phys))
> + return -ENXIO;
> +
> + ret = rmi_data_create(virt_to_phys(realm->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);
> +
> + ret = realm_create_rtt_levels(realm, ipa, level,
> + RME_RTT_MAX_LEVEL, NULL);
> + if (ret)
> + goto err;
> +
> + ret = rmi_data_create(virt_to_phys(realm->rd), dst_phys, ipa,
> + src_phys, flags);
> + }
> +
> + if (ret)
> + goto err;

ultra minor nit:

if (!ret)
return 0;

> +
> + return 0;
> +
> +err:
> + if (WARN_ON(rmi_granule_undelegate(dst_phys))) {
> + /* Page can't be returned to NS world so is lost */
> + get_page(dst_page);
> + }
> + return -ENXIO;
> +}
> +
> +static int fold_rtt(struct realm *realm, unsigned long addr, int level)
> +{
> + phys_addr_t rtt_addr;
> + int ret;
> +
> + ret = realm_rtt_fold(realm, addr, level + 1, &rtt_addr);
> + if (ret)
> + return ret;
> +
> + free_delegated_page(realm, rtt_addr);
> +
> + return 0;
> +}
> +
> +static int populate_par_region(struct kvm *kvm,
> + phys_addr_t ipa_base,
> + phys_addr_t ipa_end,
> + u32 flags)
> +{
> + struct realm *realm = &kvm->arch.realm;
> + struct kvm_memory_slot *memslot;
> + gfn_t base_gfn, end_gfn;
> + int idx;
> + phys_addr_t ipa;
> + int ret = 0;
> + struct page *tmp_page;
> + unsigned long data_flags = 0;
> +
> + base_gfn = gpa_to_gfn(ipa_base);
> + end_gfn = gpa_to_gfn(ipa_end);
> +
> + if (flags & KVM_ARM_RME_POPULATE_FLAGS_MEASURE)
> + data_flags = RMI_MEASURE_CONTENT;
> +
> + 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;
> + }
> +
> + tmp_page = alloc_page(GFP_KERNEL);
> + if (!tmp_page) {
> + ret = -ENOMEM;
> + goto out;
> + }
> +
> + mmap_read_lock(current->mm);
> +
> + ipa = ipa_base;
> + while (ipa < ipa_end) {
> + struct vm_area_struct *vma;
> + unsigned long map_size;
> + unsigned int vma_shift;
> + unsigned long offset;
> + unsigned long hva;
> + struct page *page;
> + kvm_pfn_t pfn;
> + int level;
> +
> + hva = gfn_to_hva_memslot(memslot, gpa_to_gfn(ipa));
> + vma = vma_lookup(current->mm, hva);
> + if (!vma) {
> + ret = -EFAULT;
> + break;
> + }
> +
> + if (is_vm_hugetlb_page(vma))
> + vma_shift = huge_page_shift(hstate_vma(vma));
> + else
> + vma_shift = PAGE_SHIFT;
> +
> + map_size = 1 << vma_shift;
> +
> + /*
> + * FIXME: This causes over mapping, but there's no good
> + * solution here with the ABI as it stands
> + */
> + ipa = ALIGN_DOWN(ipa, map_size);
> +
> + switch (map_size) {
> + case RME_L2_BLOCK_SIZE:
> + level = 2;
> + break;
> + case PAGE_SIZE:
> + level = 3;
> + break;
> + default:
> + WARN_ONCE(1, "Unsupport vma_shift %d", vma_shift);

Do we really need this WARNing ? Could we not fallback to the next
possible mapping size ? e.g: if 1G, we could at least try 2M. I guess
this is more or less similar to what we would do on a fault and it may
be a good idea to see if could reuse the core bits from user_mem_abort ?

> + ret = -EFAULT;
> + break;
> + }
> +
> + pfn = gfn_to_pfn_memslot(memslot, gpa_to_gfn(ipa));
> +
> + if (is_error_pfn(pfn)) {
> + ret = -EFAULT;
> + break;
> + }
> +
> + if (level < RME_RTT_MAX_LEVEL) {
> + /*
> + * A temporary RTT is needed during the map, precreate
> + * it, however if there is an error (e.g. missing
> + * parent tables) this will be handled in the
> + * realm_create_protected_data_page() call.
> + */
> + realm_create_rtt_levels(realm, ipa, level,
> + RME_RTT_MAX_LEVEL, NULL);
> + }
> +
> + page = pfn_to_page(pfn);
> +
> + for (offset = 0; offset < map_size && !ret;
> + offset += PAGE_SIZE, page++) {
> + phys_addr_t page_ipa = ipa + offset;
> +
> + ret = realm_create_protected_data_page(realm, page_ipa,
> + page, tmp_page,
> + data_flags);
> + }
> + if (ret)
> + goto err_release_pfn;
> +
> + if (level == 2) {
> + ret = fold_rtt(realm, ipa, level);
> + if (ret)
> + goto err_release_pfn;

Do we care about the FOLD error here ? Ideally we shouldn't hit an
error, but unable to fold is not an error case ? We could live with
L3 mappings ?

Suzuki

> + }
> +
> + ipa += map_size;
> + kvm_release_pfn_dirty(pfn);
> +err_release_pfn:
> + if (ret) {
> + kvm_release_pfn_clean(pfn);
> + break;
> + }
> + }
> +
> + mmap_read_unlock(current->mm);
> + __free_page(tmp_page);
> +
> +out:
> + srcu_read_unlock(&kvm->srcu, idx);
> + return ret;
> +}
> +
> +static int kvm_populate_realm(struct kvm *kvm,
> + struct kvm_cap_arm_rme_populate_realm_args *args)
> +{
> + phys_addr_t ipa_base, ipa_end;
> +
> + if (kvm_realm_state(kvm) != REALM_STATE_NEW)
> + return -EINVAL;
> +
> + if (!IS_ALIGNED(args->populate_ipa_base, PAGE_SIZE) ||
> + !IS_ALIGNED(args->populate_ipa_size, PAGE_SIZE))
> + return -EINVAL;
> +
> + if (args->flags & ~RMI_MEASURE_CONTENT)
> + return -EINVAL;
> +
> + ipa_base = args->populate_ipa_base;
> + ipa_end = ipa_base + args->populate_ipa_size;
> +
> + if (ipa_end < ipa_base)
> + return -EINVAL;
> +
> + return populate_par_region(kvm, ipa_base, ipa_end, args->flags);
> +}
> +
> static int find_map_level(struct realm *realm,
> unsigned long start,
> unsigned long end)
> @@ -808,6 +1030,18 @@ 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 kvm_cap_arm_rme_populate_realm_args 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;