Re: [RFC PATCH 16/28] arm64: RME: Allow populating initial contents

Steven Price
2023-03-10T15:55:21Z

On 06/03/2023 17:34, Zhi Wang wrote:
> On Fri, 27 Jan 2023 11:29:20 +0000
> Steven Price <steven.price@arm.com> 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.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>> arch/arm64/kvm/rme.c | 366 +++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 366 insertions(+)
>>
>> diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
>> index 16e0bfea98b1..3405b43e1421 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>
>> @@ -426,6 +427,359 @@ void kvm_realm_unmap_range(struct kvm *kvm, unsigned long ipa, u64 size)
>> }
>> }
>>
>> +static int realm_create_protected_data_page(struct realm *realm,
>> + unsigned long ipa,
>> + struct page *dst_page,
>> + struct page *tmp_page)
>> +{
>> + phys_addr_t dst_phys, tmp_phys;
>> + int ret;
>> +
>> + copy_page(page_address(tmp_page), page_address(dst_page));
>> +
>> + dst_phys = page_to_phys(dst_page);
>> + tmp_phys = page_to_phys(tmp_page);
>> +
>> + if (rmi_granule_delegate(dst_phys))
>> + return -ENXIO;
>> +
>> + ret = rmi_data_create(dst_phys, virt_to_phys(realm->rd), ipa, tmp_phys,
>> + RMI_MEASURE_CONTENT);
>> +
>> + 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(dst_phys, virt_to_phys(realm->rd), ipa,
>> + tmp_phys, RMI_MEASURE_CONTENT);
>> + }
>> +
>> + if (ret)
>> + goto err;
>> +
>> + 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(phys_addr_t rd, unsigned long addr, int level,
>> + struct realm *realm)
>> +{
>> + struct rtt_entry rtt;
>> + phys_addr_t rtt_addr;
>> +
>> + if (rmi_rtt_read_entry(rd, addr, level, &rtt))
>> + return -ENXIO;
>> +
>> + if (rtt.state != RMI_TABLE)
>> + return -EINVAL;
>> +
>> + rtt_addr = rmi_rtt_get_phys(&rtt);
>> + if (rmi_rtt_fold(rtt_addr, rd, addr, level + 1))
>> + return -ENXIO;
>> +
>> + free_delegated_page(realm, rtt_addr);
>> +
>> + return 0;
>> +}
>> +
>> +int realm_map_protected(struct realm *realm,
>> + unsigned long hva,
>> + unsigned long base_ipa,
>> + struct page *dst_page,
>> + unsigned long map_size,
>> + struct kvm_mmu_memory_cache *memcache)
>> +{
>> + phys_addr_t dst_phys = page_to_phys(dst_page);
>> + phys_addr_t rd = virt_to_phys(realm->rd);
>> + unsigned long phys = dst_phys;
>> + unsigned long ipa = base_ipa;
>> + unsigned long size;
>> + int map_level;
>> + int ret = 0;
>> +
>> + if (WARN_ON(!IS_ALIGNED(ipa, map_size)))
>> + return -EINVAL;
>> +
>> + switch (map_size) {
>> + case PAGE_SIZE:
>> + map_level = 3;
>> + break;
>> + case RME_L2_BLOCK_SIZE:
>> + map_level = 2;
>> + break;
>> + default:
>> + return -EINVAL;
>> + }
>> +
>> + if (map_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 below.
>> + */
>> + realm_create_rtt_levels(realm, ipa, map_level,
>> + RME_RTT_MAX_LEVEL, memcache);
>> + }
>> +
>> + for (size = 0; size < map_size; size += PAGE_SIZE) {
>> + if (rmi_granule_delegate(phys)) {
>> + struct rtt_entry rtt;
>> +
>> + /*
>> + * It's possible we raced with another VCPU on the same
>> + * fault. If the entry exists and matches then exit
>> + * early and assume the other VCPU will handle the
>> + * mapping.
>> + */
>> + if (rmi_rtt_read_entry(rd, ipa, RME_RTT_MAX_LEVEL, &rtt))
>> + goto err;
>> +
>> + // FIXME: For a block mapping this could race at level
>> + // 2 or 3...
>> + if (WARN_ON((rtt.walk_level != RME_RTT_MAX_LEVEL ||
>> + rtt.state != RMI_ASSIGNED ||
>> + rtt.desc != phys))) {
>> + goto err;
>> + }
>> +
>> + return 0;
>> + }
>> +
>> + ret = rmi_data_create_unknown(phys, rd, ipa);
>> +
>> + 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,
>> + memcache);
>> + WARN_ON(ret);
>> + if (ret)
>> + goto err_undelegate;
>> +
>> + ret = rmi_data_create_unknown(phys, rd, ipa);
>> + }
>> + WARN_ON(ret);
>> +
>> + if (ret)
>> + goto err_undelegate;
>> +
>> + phys += PAGE_SIZE;
>> + ipa += PAGE_SIZE;
>> + }
>> +
>> + if (map_size == RME_L2_BLOCK_SIZE)
>> + ret = fold_rtt(rd, base_ipa, map_level, realm);
>> + if (WARN_ON(ret))
>> + goto err;
>> +
>> + return 0;
>> +
>> +err_undelegate:
>> + if (WARN_ON(rmi_granule_undelegate(phys))) {
>> + /* Page can't be returned to NS world so is lost */
>> + get_page(phys_to_page(phys));
>> + }
>> +err:
>> + while (size > 0) {
>> + phys -= PAGE_SIZE;
>> + size -= PAGE_SIZE;
>> + ipa -= PAGE_SIZE;
>> +
>> + rmi_data_destroy(rd, ipa);
>> +
>> + if (WARN_ON(rmi_granule_undelegate(phys))) {
>> + /* Page can't be returned to NS world so is lost */
>> + get_page(phys_to_page(phys));
>> + }
>> + }
>> + return -ENXIO;
>> +}
>> +
>
> There seems no caller to the function above. Better move it to the related
> patch.

Indeed this should really be in the next patch - will move as it's very
confusing having it in this patch (sorry about that).

>> +static int populate_par_region(struct kvm *kvm,
>> + phys_addr_t ipa_base,
>> + phys_addr_t ipa_end)
>> +{
>> + 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;
>> + phys_addr_t rd = virt_to_phys(realm->rd);
>> +
>> + 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;
>> + }
>> +
>> + 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);
>> + ret = -EFAULT;
>> + break;
>> + }
>> +
>> + pfn = gfn_to_pfn_memslot(memslot, gpa_to_gfn(ipa));
>> +
>> + if (is_error_pfn(pfn)) {
>> + ret = -EFAULT;
>> + break;
>> + }
>> +
>> + ret = rmi_rtt_init_ripas(rd, ipa, level);
>> + if (RMI_RETURN_STATUS(ret) == RMI_ERROR_RTT) {
>> + ret = realm_create_rtt_levels(realm, ipa,
>> + RMI_RETURN_INDEX(ret),
>> + level, NULL);
>> + if (ret)
>> + break;
>> + ret = rmi_rtt_init_ripas(rd, ipa, level);
>> + if (ret) {
>> + ret = -ENXIO;
>> + 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);
>> + }
>> + if (ret)
>> + goto err_release_pfn;
>> +
>> + if (level == 2) {
>> + ret = fold_rtt(rd, ipa, level, realm);
>> + if (ret)
>> + goto err_release_pfn;
>> + }
>> +
>> + ipa += map_size;
>
>> + kvm_set_pfn_accessed(pfn);
>> + kvm_set_pfn_dirty(pfn);
>
> kvm_release_pfn_dirty() has already called kvm_set_pfn_{accessed, dirty}().

Will remove those calls.

>> + 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;
>> +
>
> Check kvm_is_realm(kvm) here or in the kvm_realm_enable_cap().

I'm going to update kvm_vm_ioctl_enable_cap() to check kvm_is_realm() so
we won't get here.

>> + if (kvm_realm_state(kvm) != REALM_STATE_NEW)
>> + return -EBUSY;
>
> Maybe -EINVAL? The realm hasn't been created (RMI_REALM_CREATE is not called
> yet). The userspace shouldn't reach this path.

Well user space can attempt to populate in the ACTIVE state - which is
where the idea of 'busy' comes from. Admittedly it's a little confusing
when RMI_REALM_CREATE hasn't been called.

I'm not particularly bothered about the return code, but it's useful to
have a different code to -EINVAL as it's not an invalid argument, but
calling at the wrong time. I can't immediately see a better error code
though.

Steve

>> +
>> + if (!IS_ALIGNED(args->populate_ipa_base, PAGE_SIZE) ||
>> + !IS_ALIGNED(args->populate_ipa_size, PAGE_SIZE))
>> + 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);
>> +}
>> +
>> static int set_ipa_state(struct kvm_vcpu *vcpu,
>> unsigned long ipa,
>> unsigned long end,
>> @@ -748,6 +1102,18 @@ 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;
>