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

Zhi Wang
2023-03-14T15:32:26Z

On Fri, 10 Mar 2023 15:47:16 +0000
Steven Price <steven.price@arm.com> wrote:

> 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.
>
The reason why I feel -EBUSY is little bit off is EBUSY usually indicates
something is already initialized and currently running, then another
calling path wanna to operate it.

I took a look on the ioctls in arch/arm64/kvm/arm.c. It seems people have
different opinions for calling execution path at a wrong time:

For example:

long kvm_arch_vcpu_ioctl()
...
case KVM_GET_REG_LIST: {
struct kvm_reg_list __user *user_list = argp;
struct kvm_reg_list reg_list;
unsigned n;

r = -ENOEXEC;
if (unlikely(!kvm_vcpu_initialized(vcpu)))
break;

r = -EPERM;
if (!kvm_arm_vcpu_is_finalized(vcpu))
break;

If we have to choose one, I prefer -ENOEXEC as -EPERM is stranger. But
personally my vote goes to -EINVAL.

> 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;
> >
>