long kvm_vm_ioctl_mte_copy_tags()

in kvm/guest.c [1011:1095]

• 63 lines of code
• 15 McCabe index (conditional complexity)

long kvm_vm_ioctl_mte_copy_tags(struct kvm *kvm,
				struct kvm_arm_copy_mte_tags *copy_tags)
{
	gpa_t guest_ipa = copy_tags->guest_ipa;
	size_t length = copy_tags->length;
	void __user *tags = copy_tags->addr;
	gpa_t gfn;
	bool write = !(copy_tags->flags & KVM_ARM_TAGS_FROM_GUEST);
	int ret = 0;

	if (!kvm_has_mte(kvm))
		return -EINVAL;

	if (copy_tags->reserved[0] || copy_tags->reserved[1])
		return -EINVAL;

	if (copy_tags->flags & ~KVM_ARM_TAGS_FROM_GUEST)
		return -EINVAL;

	if (length & ~PAGE_MASK || guest_ipa & ~PAGE_MASK)
		return -EINVAL;

	gfn = gpa_to_gfn(guest_ipa);

	mutex_lock(&kvm->slots_lock);

	while (length > 0) {
		kvm_pfn_t pfn = gfn_to_pfn_prot(kvm, gfn, write, NULL);
		void *maddr;
		unsigned long num_tags;
		struct page *page;

		if (is_error_noslot_pfn(pfn)) {
			ret = -EFAULT;
			goto out;
		}

		page = pfn_to_online_page(pfn);
		if (!page) {
			/* Reject ZONE_DEVICE memory */
			ret = -EFAULT;
			goto out;
		}
		maddr = page_address(page);

		if (!write) {
			if (test_bit(PG_mte_tagged, &page->flags))
				num_tags = mte_copy_tags_to_user(tags, maddr,
							MTE_GRANULES_PER_PAGE);
			else
				/* No tags in memory, so write zeros */
				num_tags = MTE_GRANULES_PER_PAGE -
					clear_user(tags, MTE_GRANULES_PER_PAGE);
			kvm_release_pfn_clean(pfn);
		} else {
			num_tags = mte_copy_tags_from_user(maddr, tags,
							MTE_GRANULES_PER_PAGE);

			/*
			 * Set the flag after checking the write
			 * completed fully
			 */
			if (num_tags == MTE_GRANULES_PER_PAGE)
				set_bit(PG_mte_tagged, &page->flags);

			kvm_release_pfn_dirty(pfn);
		}

		if (num_tags != MTE_GRANULES_PER_PAGE) {
			ret = -EFAULT;
			goto out;
		}

		gfn++;
		tags += num_tags;
		length -= PAGE_SIZE;
	}

out:
	mutex_unlock(&kvm->slots_lock);
	/* If some data has been copied report the number of bytes copied */
	if (length != copy_tags->length)
		return copy_tags->length - length;
	return ret;
}