Re: [PATCH v4 09/43] arm64: RME: ioctls to create and configure realms

[Shanker Donthineni <sdonthineni@nvidia.com>]

On 8/21/24 10:38, Steven Price wrote:
> External email: Use caution opening links or attachments
> 
> 
> Add the KVM_CAP_ARM_RME_CREATE_RD ioctl to create a realm. This involves
> delegating pages to the RMM to hold the Realm Descriptor (RD) and for
> the base level of the Realm Translation Tables (RTT). A VMID also need
> to be picked, since the RMM has a separate VMID address space a
> dedicated allocator is added for this purpose.
> 
> KVM_CAP_ARM_RME_CONFIG_REALM is provided to allow configuring the realm
> before it is created. Configuration options can be classified as:
> 
>   1. Parameters specific to the Realm stage2 (e.g. IPA Size, vmid, stage2
>      entry level, entry level RTTs, number of RTTs in start level, LPA2)
>      Most of these are not measured by RMM and comes from KVM book
>      keeping.
> 
>   2. Parameters controlling "Arm Architecture features for the VM". (e.g.
>      SVE VL, PMU counters, number of HW BRPs/WPs), configured by the VMM
>      using the "user ID register write" mechanism. These will be
>      supported in the later patches.
> 
>   3. Parameters are not part of the core Arm architecture but defined
>      by the RMM spec (e.g. Hash algorithm for measurement,
>      Personalisation value). These are programmed via
>      KVM_CAP_ARM_RME_CONFIG_REALM.
> 
> For the IPA size there is the possibility that the RMM supports a
> different size to the IPA size supported by KVM for normal guests. At
> the moment the 'normal limit' is exposed by KVM_CAP_ARM_VM_IPA_SIZE and
> the IPA size is configured by the bottom bits of vm_type in
> KVM_CREATE_VM. This means that it isn't easy for the VMM to discover
> what IPA sizes are supported for Realm guests. Since the IPA is part of
> the measurement of the realm guest the current expectation is that the
> VMM will be required to pick the IPA size demanded by attestation and
> therefore simply failing if this isn't available is fine. An option
> would be to expose a new capability ioctl to obtain the RMM's maximum
> IPA size if this is needed in the future.
> 
> 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>
> ---
> Changes since v2:
>   * Improved commit description.
>   * Improved return failures for rmi_check_version().
>   * Clear contents of PGD after it has been undelegated in case the RMM
>     left stale data.
>   * Minor changes to reflect changes in previous patches.
> ---
>   arch/arm64/include/asm/kvm_emulate.h |   5 +
>   arch/arm64/include/asm/kvm_rme.h     |  19 ++
>   arch/arm64/kvm/arm.c                 |  18 ++
>   arch/arm64/kvm/mmu.c                 |  20 +-
>   arch/arm64/kvm/rme.c                 | 283 +++++++++++++++++++++++++++
>   5 files changed, 341 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index c7bfb6788c96..5edcfb1b6c68 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -705,6 +705,11 @@ static inline enum realm_state kvm_realm_state(struct kvm *kvm)
>          return READ_ONCE(kvm->arch.realm.state);
>   }
> 
> +static inline bool kvm_realm_is_created(struct kvm *kvm)
> +{
> +       return kvm_is_realm(kvm) && kvm_realm_state(kvm) != REALM_STATE_NONE;
> +}
> +
>   static inline bool vcpu_is_rec(struct kvm_vcpu *vcpu)
>   {
>          return false;
> diff --git a/arch/arm64/include/asm/kvm_rme.h b/arch/arm64/include/asm/kvm_rme.h
> index 69af5c3a1e44..209cd99f03dd 100644
> --- a/arch/arm64/include/asm/kvm_rme.h
> +++ b/arch/arm64/include/asm/kvm_rme.h
> @@ -6,6 +6,8 @@
>   #ifndef __ASM_KVM_RME_H
>   #define __ASM_KVM_RME_H
> 
> +#include <uapi/linux/kvm.h>
> +
>   /**
>    * enum realm_state - State of a Realm
>    */
> @@ -46,11 +48,28 @@ enum realm_state {
>    * struct realm - Additional per VM data for a Realm
>    *
>    * @state: The lifetime state machine for the realm
> + * @rd: Kernel mapping of the Realm Descriptor (RD)
> + * @params: Parameters for the RMI_REALM_CREATE command
> + * @num_aux: The number of auxiliary pages required by the RMM
> + * @vmid: VMID to be used by the RMM for the realm
> + * @ia_bits: Number of valid Input Address bits in the IPA
>    */
>   struct realm {
>          enum realm_state state;
> +
> +       void *rd;
> +       struct realm_params *params;
> +
> +       unsigned long num_aux;
> +       unsigned int vmid;
> +       unsigned int ia_bits;
>   };
> 
>   void kvm_init_rme(void);
> +u32 kvm_realm_ipa_limit(void);
> +
> +int kvm_realm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap);
> +int kvm_init_realm_vm(struct kvm *kvm);
> +void kvm_destroy_realm(struct kvm *kvm);
> 
>   #endif
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 71ffcc766eeb..15c7c2cabbf7 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -152,6 +152,13 @@ int kvm_vm_ioctl_enable_cap(struct kvm *kvm,
>                  }
>                  mutex_unlock(&kvm->slots_lock);
>                  break;
> +       case KVM_CAP_ARM_RME:
> +               if (!kvm_is_realm(kvm))
> +                       return -EINVAL;
> +               mutex_lock(&kvm->lock);
> +               r = kvm_realm_enable_cap(kvm, cap);
> +               mutex_unlock(&kvm->lock);
> +               break;
>          default:
>                  break;
>          }
> @@ -213,6 +220,13 @@ int kvm_arch_init_vm(struct kvm *kvm, unsigned long type)
> 
>          bitmap_zero(kvm->arch.vcpu_features, KVM_VCPU_MAX_FEATURES);
> 
> +       /* Initialise the realm bits after the generic bits are enabled */
> +       if (kvm_is_realm(kvm)) {
> +               ret = kvm_init_realm_vm(kvm);
> +               if (ret)
> +                       goto err_free_cpumask;
> +       }
> +
>          return 0;
> 
>   err_free_cpumask:
> @@ -271,6 +285,7 @@ void kvm_arch_destroy_vm(struct kvm *kvm)
>          kvm_unshare_hyp(kvm, kvm + 1);
> 
>          kvm_arm_teardown_hypercalls(kvm);
> +       kvm_destroy_realm(kvm);
>   }
> 
>   static bool kvm_has_full_ptr_auth(void)
> @@ -418,6 +433,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
>          case KVM_CAP_ARM_SUPPORTED_REG_MASK_RANGES:
>                  r = BIT(0);
>                  break;
> +       case KVM_CAP_ARM_RME:
> +               r = static_key_enabled(&kvm_rme_is_available);
> +               break;
>          default:
>                  r = 0;
>          }
> diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c
> index 6981b1bc0946..2257a3b4fb06 100644
> --- a/arch/arm64/kvm/mmu.c
> +++ b/arch/arm64/kvm/mmu.c
> @@ -862,11 +862,16 @@ static struct kvm_pgtable_mm_ops kvm_s2_mm_ops = {
>          .icache_inval_pou       = invalidate_icache_guest_page,
>   };
> 
> -static int kvm_init_ipa_range(struct kvm_s2_mmu *mmu, unsigned long type)
> +static int kvm_init_ipa_range(struct kvm *kvm,
> +                             struct kvm_s2_mmu *mmu, unsigned long type)
>   {
>          u32 kvm_ipa_limit = get_kvm_ipa_limit();
>          u64 mmfr0, mmfr1;
>          u32 phys_shift;
> +       u32 ipa_limit = kvm_ipa_limit;
> +
> +       if (kvm_is_realm(kvm))
> +               ipa_limit = kvm_realm_ipa_limit();
> 
>          if (type & ~KVM_VM_TYPE_ARM_IPA_SIZE_MASK)
>                  return -EINVAL;
> @@ -875,12 +880,12 @@ static int kvm_init_ipa_range(struct kvm_s2_mmu *mmu, unsigned long type)
>          if (is_protected_kvm_enabled()) {
>                  phys_shift = kvm_ipa_limit;
>          } else if (phys_shift) {
> -               if (phys_shift > kvm_ipa_limit ||
> +               if (phys_shift > ipa_limit ||
>                      phys_shift < ARM64_MIN_PARANGE_BITS)
>                          return -EINVAL;
>          } else {
>                  phys_shift = KVM_PHYS_SHIFT;
> -               if (phys_shift > kvm_ipa_limit) {
> +               if (phys_shift > ipa_limit) {
>                          pr_warn_once("%s using unsupported default IPA limit, upgrade your VMM\n",
>                                       current->comm);
>                          return -EINVAL;
> @@ -932,7 +937,7 @@ int kvm_init_stage2_mmu(struct kvm *kvm, struct kvm_s2_mmu *mmu, unsigned long t
>                  return -EINVAL;
>          }
> 
> -       err = kvm_init_ipa_range(mmu, type);
> +       err = kvm_init_ipa_range(kvm, mmu, type);
>          if (err)
>                  return err;
> 
> @@ -1055,6 +1060,13 @@ void kvm_free_stage2_pgd(struct kvm_s2_mmu *mmu)
>          struct kvm_pgtable *pgt = NULL;
> 
>          write_lock(&kvm->mmu_lock);
> +       if (kvm_is_realm(kvm) &&
> +           (kvm_realm_state(kvm) != REALM_STATE_DEAD &&
> +            kvm_realm_state(kvm) != REALM_STATE_NONE)) {
> +               /* Tearing down RTTs will be added in a later patch */
> +               write_unlock(&kvm->mmu_lock);
> +               return;
> +       }
>          pgt = mmu->pgt;
>          if (pgt) {
>                  mmu->pgd_phys = 0;
> diff --git a/arch/arm64/kvm/rme.c b/arch/arm64/kvm/rme.c
> index 418685fbf6ed..4d21ec5f2910 100644
> --- a/arch/arm64/kvm/rme.c
> +++ b/arch/arm64/kvm/rme.c
> @@ -5,9 +5,20 @@
> 
>   #include <linux/kvm_host.h>
> 
> +#include <asm/kvm_emulate.h>
> +#include <asm/kvm_mmu.h>
>   #include <asm/rmi_cmds.h>
>   #include <asm/virt.h>
> 
> +#include <asm/kvm_pgtable.h>
> +
> +static unsigned long rmm_feat_reg0;
> +
> +static bool rme_supports(unsigned long feature)
> +{
> +       return !!u64_get_bits(rmm_feat_reg0, feature);
> +}
> +
>   static int rmi_check_version(void)
>   {
>          struct arm_smccc_res res;
> @@ -36,6 +47,272 @@ static int rmi_check_version(void)
>          return 0;
>   }
> 
> +u32 kvm_realm_ipa_limit(void)
> +{
> +       return u64_get_bits(rmm_feat_reg0, RMI_FEATURE_REGISTER_0_S2SZ);
> +}
> +
> +static int get_start_level(struct realm *realm)
> +{
> +       return 4 - stage2_pgtable_levels(realm->ia_bits);
> +}
> +
> +static int realm_create_rd(struct kvm *kvm)
> +{
> +       struct realm *realm = &kvm->arch.realm;
> +       struct realm_params *params = realm->params;
> +       void *rd = NULL;
> +       phys_addr_t rd_phys, params_phys;
> +       struct kvm_pgtable *pgt = kvm->arch.mmu.pgt;
> +       int i, r;
> +
> +       if (WARN_ON(realm->rd) || WARN_ON(!realm->params))
> +               return -EEXIST;
> +
> +       rd = (void *)__get_free_page(GFP_KERNEL);
> +       if (!rd)
> +               return -ENOMEM;
> +
> +       rd_phys = virt_to_phys(rd);
> +       if (rmi_granule_delegate(rd_phys)) {
> +               r = -ENXIO;
> +               goto free_rd;
> +       }
> +
> +       for (i = 0; i < pgt->pgd_pages; i++) {
> +               phys_addr_t pgd_phys = kvm->arch.mmu.pgd_phys + i * PAGE_SIZE;
> +
> +               if (rmi_granule_delegate(pgd_phys)) {
> +                       r = -ENXIO;
> +                       goto out_undelegate_tables;
> +               }
> +       }
> +
> +       realm->ia_bits = VTCR_EL2_IPA(kvm->arch.mmu.vtcr);
> +
> +       params->s2sz = VTCR_EL2_IPA(kvm->arch.mmu.vtcr);
> +       params->rtt_level_start = get_start_level(realm);
> +       params->rtt_num_start = pgt->pgd_pages;
> +       params->rtt_base = kvm->arch.mmu.pgd_phys;
> +       params->vmid = realm->vmid;
> +
> +       params_phys = virt_to_phys(params);
> +
> +       if (rmi_realm_create(rd_phys, params_phys)) {
> +               r = -ENXIO;
> +               goto out_undelegate_tables;
> +       }
> +
> +       realm->rd = rd;
> +
> +       if (WARN_ON(rmi_rec_aux_count(rd_phys, &realm->num_aux))) {
> +               WARN_ON(rmi_realm_destroy(rd_phys));
> +               goto out_undelegate_tables;
> +       }
> +
> +       return 0;
> +
> +out_undelegate_tables:
> +       while (--i >= 0) {
> +               phys_addr_t pgd_phys = kvm->arch.mmu.pgd_phys + i * PAGE_SIZE;
> +
> +               WARN_ON(rmi_granule_undelegate(pgd_phys));
> +       }
> +       WARN_ON(rmi_granule_undelegate(rd_phys));
> +free_rd:
> +       free_page((unsigned long)rd);
> +       return r;
> +}
> +
> +/* Protects access to rme_vmid_bitmap */
> +static DEFINE_SPINLOCK(rme_vmid_lock);
> +static unsigned long *rme_vmid_bitmap;
> +
> +static int rme_vmid_init(void)
> +{
> +       unsigned int vmid_count = 1 << kvm_get_vmid_bits();
> +
> +       rme_vmid_bitmap = bitmap_zalloc(vmid_count, GFP_KERNEL);
> +       if (!rme_vmid_bitmap) {
> +               kvm_err("%s: Couldn't allocate rme vmid bitmap\n", __func__);
> +               return -ENOMEM;
> +       }
> +
> +       return 0;
> +}
> +
> +static int rme_vmid_reserve(void)
> +{
> +       int ret;
> +       unsigned int vmid_count = 1 << kvm_get_vmid_bits();
> +
> +       spin_lock(&rme_vmid_lock);
> +       ret = bitmap_find_free_region(rme_vmid_bitmap, vmid_count, 0);
> +       spin_unlock(&rme_vmid_lock);
> +
> +       return ret;
> +}
> +
> +static void rme_vmid_release(unsigned int vmid)
> +{
> +       spin_lock(&rme_vmid_lock);
> +       bitmap_release_region(rme_vmid_bitmap, vmid, 0);
> +       spin_unlock(&rme_vmid_lock);
> +}
> +
> +static int kvm_create_realm(struct kvm *kvm)
> +{
> +       struct realm *realm = &kvm->arch.realm;
> +       int ret;
> +
> +       if (!kvm_is_realm(kvm))
> +               return -EINVAL;
> +       if (kvm_realm_is_created(kvm))
> +               return -EEXIST;
> +
> +       ret = rme_vmid_reserve();
> +       if (ret < 0)
> +               return ret;
> +       realm->vmid = ret;
> +
> +       ret = realm_create_rd(kvm);
> +       if (ret) {
> +               rme_vmid_release(realm->vmid);
> +               return ret;
> +       }
> +
> +       WRITE_ONCE(realm->state, REALM_STATE_NEW);
> +
> +       /* The realm is up, free the parameters.  */
> +       free_page((unsigned long)realm->params);
> +       realm->params = NULL;
Is there a specific reason for freeing the params? The pointer is
referenced in rtt_get_phys() without a NULL check, which leads to
a kernel crash.

static phys_addr_t rtt_get_phys(struct realm *realm, struct rtt_entry *rtt)
{
         bool lpa2 = realm->params->flags & RMI_REALM_PARAM_FLAG_LPA2;

> +
> +       return 0;
> +}
> +
> +static int config_realm_hash_algo(struct realm *realm,
> +                                 struct kvm_cap_arm_rme_config_item *cfg)
> +{
> +       switch (cfg->hash_algo) {
> +       case KVM_CAP_ARM_RME_MEASUREMENT_ALGO_SHA256:
> +               if (!rme_supports(RMI_FEATURE_REGISTER_0_HASH_SHA_256))
> +                       return -EINVAL;
> +               break;
> +       case KVM_CAP_ARM_RME_MEASUREMENT_ALGO_SHA512:
> +               if (!rme_supports(RMI_FEATURE_REGISTER_0_HASH_SHA_512))
> +                       return -EINVAL;
> +               break;
> +       default:
> +               return -EINVAL;
> +       }
> +       realm->params->hash_algo = cfg->hash_algo;
> +       return 0;
> +}
> +
> +static int kvm_rme_config_realm(struct kvm *kvm, struct kvm_enable_cap *cap)
> +{
> +       struct kvm_cap_arm_rme_config_item cfg;
> +       struct realm *realm = &kvm->arch.realm;
> +       int r = 0;
> +
> +       if (kvm_realm_is_created(kvm))
> +               return -EBUSY;
> +
> +       if (copy_from_user(&cfg, (void __user *)cap->args[1], sizeof(cfg)))
> +               return -EFAULT;
> +
> +       switch (cfg.cfg) {
> +       case KVM_CAP_ARM_RME_CFG_RPV:
> +               memcpy(&realm->params->rpv, &cfg.rpv, sizeof(cfg.rpv));
> +               break;
> +       case KVM_CAP_ARM_RME_CFG_HASH_ALGO:
> +               r = config_realm_hash_algo(realm, &cfg);
> +               break;
> +       default:
> +               r = -EINVAL;
> +       }
> +
> +       return r;
> +}
> +
> +int kvm_realm_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap)
> +{
> +       int r = 0;
> +
> +       if (!kvm_is_realm(kvm))
> +               return -EINVAL;
> +
> +       switch (cap->args[0]) {
> +       case KVM_CAP_ARM_RME_CONFIG_REALM:
> +               r = kvm_rme_config_realm(kvm, cap);
> +               break;
> +       case KVM_CAP_ARM_RME_CREATE_RD:
> +               r = kvm_create_realm(kvm);
> +               break;
> +       default:
> +               r = -EINVAL;
> +               break;
> +       }
> +
> +       return r;
> +}
> +
> +void kvm_destroy_realm(struct kvm *kvm)
> +{
> +       struct realm *realm = &kvm->arch.realm;
> +       struct kvm_pgtable *pgt = kvm->arch.mmu.pgt;
> +       int i;
> +
> +       if (realm->params) {
> +               free_page((unsigned long)realm->params);
> +               realm->params = NULL;
> +       }
> +
> +       if (!kvm_realm_is_created(kvm))
> +               return;
> +
> +       WRITE_ONCE(realm->state, REALM_STATE_DYING);
> +
> +       if (realm->rd) {
> +               phys_addr_t rd_phys = virt_to_phys(realm->rd);
> +
> +               if (WARN_ON(rmi_realm_destroy(rd_phys)))
> +                       return;
> +               if (WARN_ON(rmi_granule_undelegate(rd_phys)))
> +                       return;
> +               free_page((unsigned long)realm->rd);
> +               realm->rd = NULL;
> +       }
> +
> +       rme_vmid_release(realm->vmid);
> +
> +       for (i = 0; i < pgt->pgd_pages; i++) {
> +               phys_addr_t pgd_phys = kvm->arch.mmu.pgd_phys + i * PAGE_SIZE;
> +
> +               if (WARN_ON(rmi_granule_undelegate(pgd_phys)))
> +                       return;
> +
> +               clear_page(phys_to_virt(pgd_phys));
> +       }
> +
> +       WRITE_ONCE(realm->state, REALM_STATE_DEAD);
> +
> +       /* Now that the Realm is destroyed, free the entry level RTTs */
> +       kvm_free_stage2_pgd(&kvm->arch.mmu);
> +}
> +
> +int kvm_init_realm_vm(struct kvm *kvm)
> +{
> +       struct realm_params *params;
> +
> +       params = (struct realm_params *)get_zeroed_page(GFP_KERNEL);
> +       if (!params)
> +               return -ENOMEM;
> +
> +       kvm->arch.realm.params = params;
> +       return 0;
> +}
> +
>   void kvm_init_rme(void)
>   {
>          if (PAGE_SIZE != SZ_4K)
> @@ -46,5 +323,11 @@ void kvm_init_rme(void)
>                  /* Continue without realm support */
>                  return;
> 
> +       if (WARN_ON(rmi_features(0, &rmm_feat_reg0)))
> +               return;
> +
> +       if (rme_vmid_init())
> +               return;
> +
>          /* Future patch will enable static branch kvm_rme_is_available */
>   }
> --
> 2.34.1
>