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

[Steven Price]

On 06/03/2023 17:34, Zhi Wang wrote:
> On Fri, 27 Jan 2023 11:29:20 +0000
> Steven Price <steven.price@xxxxxxx> 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@xxxxxxx>
>> ---
>>  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;
>