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

[Zhi Wang <zhi.wang.linux@gmail.com>]

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.

> +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}().

> +		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().

> +	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.

> +
> +	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;