path: root/arch/powerpc/kvm/book3s_64_vio.c

/*
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License, version 2, as
 * published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 * Copyright 2010 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
 * Copyright 2011 David Gibson, IBM Corporation <dwg@au1.ibm.com>
 * Copyright 2016 Alexey Kardashevskiy, IBM Corporation <aik@au1.ibm.com>
 */

#include <linux/types.h>
#include <linux/string.h>
#include <linux/kvm.h>
#include <linux/kvm_host.h>
#include <linux/highmem.h>
#include <linux/gfp.h>
#include <linux/slab.h>
#include <linux/sched/signal.h>
#include <linux/hugetlb.h>
#include <linux/list.h>
#include <linux/anon_inodes.h>
#include <linux/iommu.h>
#include <linux/file.h>

#include <asm/kvm_ppc.h>
#include <asm/kvm_book3s.h>
#include <asm/book3s/64/mmu-hash.h>
#include <asm/hvcall.h>
#include <asm/synch.h>
#include <asm/ppc-opcode.h>
#include <asm/kvm_host.h>
#include <asm/udbg.h>
#include <asm/iommu.h>
#include <asm/tce.h>
#include <asm/mmu_context.h>

static unsigned long kvmppc_tce_pages(unsigned long iommu_pages)
{
	return ALIGN(iommu_pages * sizeof(u64), PAGE_SIZE) / PAGE_SIZE;
}

static unsigned long kvmppc_stt_pages(unsigned long tce_pages)
{
	unsigned long stt_bytes = sizeof(struct kvmppc_spapr_tce_table) +
			(tce_pages * sizeof(struct page *));

	return tce_pages + ALIGN(stt_bytes, PAGE_SIZE) / PAGE_SIZE;
}

static long kvmppc_account_memlimit(unsigned long stt_pages, bool inc)
{
	long ret = 0;

	if (!current || !current->mm)
		return ret; /* process exited */

	down_write(&current->mm->mmap_sem);

	if (inc) {
		unsigned long locked, lock_limit;

		locked = current->mm->locked_vm + stt_pages;
		lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
		if (locked > lock_limit && !capable(CAP_IPC_LOCK))
			ret = -ENOMEM;
		else
			current->mm->locked_vm += stt_pages;
	} else {
		if (WARN_ON_ONCE(stt_pages > current->mm->locked_vm))
			stt_pages = current->mm->locked_vm;

		current->mm->locked_vm -= stt_pages;
	}

	pr_debug("[%d] RLIMIT_MEMLOCK KVM %c%ld %ld/%ld%s\n", current->pid,
			inc ? '+' : '-',
			stt_pages << PAGE_SHIFT,
			current->mm->locked_vm << PAGE_SHIFT,
			rlimit(RLIMIT_MEMLOCK),
			ret ? " - exceeded" : "");

	up_write(&current->mm->mmap_sem);

	return ret;
}

static void kvm_spapr_tce_iommu_table_free(struct rcu_head *head)
{
	struct kvmppc_spapr_tce_iommu_table *stit = container_of(head,
			struct kvmppc_spapr_tce_iommu_table, rcu);

	iommu_tce_table_put(stit->tbl);

	kfree(stit);
}

static void kvm_spapr_tce_liobn_put(struct kref *kref)
{
	struct kvmppc_spapr_tce_iommu_table *stit = container_of(kref,
			struct kvmppc_spapr_tce_iommu_table, kref);

	list_del_rcu(&stit->next);

	call_rcu(&stit->rcu, kvm_spapr_tce_iommu_table_free);
}

extern void kvm_spapr_tce_release_iommu_group(struct kvm *kvm,
		struct iommu_group *grp)
{
	int i;
	struct kvmppc_spapr_tce_table *stt;
	struct kvmppc_spapr_tce_iommu_table *stit, *tmp;
	struct iommu_table_group *table_group = NULL;

	list_for_each_entry_rcu(stt, &kvm->arch.spapr_tce_tables, list) {

		table_group = iommu_group_get_iommudata(grp);
		if (WARN_ON(!table_group))
			continue;

		list_for_each_entry_safe(stit, tmp, &stt->iommu_tables, next) {
			for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
				if (table_group->tables[i] != stit->tbl)
					continue;

				kref_put(&stit->kref, kvm_spapr_tce_liobn_put);
			}
		}
	}
}

extern long kvm_spapr_tce_attach_iommu_group(struct kvm *kvm, int tablefd,
		struct iommu_group *grp)
{
	struct kvmppc_spapr_tce_table *stt = NULL;
	bool found = false;
	struct iommu_table *tbl = NULL;
	struct iommu_table_group *table_group;
	long i;
	struct kvmppc_spapr_tce_iommu_table *stit;
	struct fd f;

	f = fdget(tablefd);
	if (!f.file)
		return -EBADF;

	list_for_each_entry_rcu(stt, &kvm->arch.spapr_tce_tables, list) {
		if (stt == f.file->private_data) {
			found = true;
			break;
		}
	}

	fdput(f);

	if (!found)
		return -EINVAL;

	table_group = iommu_group_get_iommudata(grp);
	if (WARN_ON(!table_group))
		return -EFAULT;

	for (i = 0; i < IOMMU_TABLE_GROUP_MAX_TABLES; ++i) {
		struct iommu_table *tbltmp = table_group->tables[i];

		if (!tbltmp)
			continue;
		/* Make sure hardware table parameters are compatible */
		if ((tbltmp->it_page_shift <= stt->page_shift) &&
				(tbltmp->it_offset << tbltmp->it_page_shift ==
				 stt->offset << stt->page_shift) &&
				(tbltmp->it_size << tbltmp->it_page_shift >=
				 stt->size << stt->page_shift)) {
			/*
			 * Reference the table to avoid races with
			 * add/remove DMA windows.
			 */
			tbl = iommu_tce_table_get(tbltmp);
			break;
		}
	}
	if (!tbl)
		return -EINVAL;

	list_for_each_entry_rcu(stit, &stt->iommu_tables, next) {
		if (tbl != stit->tbl)
			continue;

		if (!kref_get_unless_zero(&stit->kref)) {
			/* stit is being destroyed */
			iommu_tce_table_put(tbl);
			return -ENOTTY;
		}
		/*
		 * The table is already known to this KVM, we just increased
		 * its KVM reference counter and can return.
		 */
		return 0;
	}

	stit = kzalloc(sizeof(*stit), GFP_KERNEL);
	if (!stit) {
		iommu_tce_table_put(tbl);
		return -ENOMEM;
	}

	stit->tbl = tbl;
	kref_init(&stit->kref);

	list_add_rcu(&stit->next, &stt->iommu_tables);

	return 0;
}

static void release_spapr_tce_table(struct rcu_head *head)
{
	struct kvmppc_spapr_tce_table *stt = container_of(head,
			struct kvmppc_spapr_tce_table, rcu);
	unsigned long i, npages = kvmppc_tce_pages(stt->size);

	for (i = 0; i < npages; i++)
		if (stt->pages[i])
			__free_page(stt->pages[i]);

	kfree(stt);
}

static struct page *kvm_spapr_get_tce_page(struct kvmppc_spapr_tce_table *stt,
		unsigned long sttpage)
{
	struct page *page = stt->pages[sttpage];

	if (page)
		return page;

	mutex_lock(&stt->alloc_lock);
	page = stt->pages[sttpage];
	if (!page) {
		page = alloc_page(GFP_KERNEL | __GFP_ZERO);
		WARN_ON_ONCE(!page);
		if (page)
			stt->pages[sttpage] = page;
	}
	mutex_unlock(&stt->alloc_lock);

	return page;
}

static vm_fault_t kvm_spapr_tce_fault(struct vm_fault *vmf)
{
	struct kvmppc_spapr_tce_table *stt = vmf->vma->vm_file->private_data;
	struct page *page;

	if (vmf->pgoff >= kvmppc_tce_pages(stt->size))
		return VM_FAULT_SIGBUS;

	page = kvm_spapr_get_tce_page(stt, vmf->pgoff);
	if (!page)
		return VM_FAULT_OOM;

	get_page(page);
	vmf->page = page;
	return 0;
}

static const struct vm_operations_struct kvm_spapr_tce_vm_ops = {
	.fault = kvm_spapr_tce_fault,
};

static int kvm_spapr_tce_mmap(struct file *file, struct vm_area_struct *vma)
{
	vma->vm_ops = &kvm_spapr_tce_vm_ops;
	return 0;
}

static int kvm_spapr_tce_release(struct inode *inode, struct file *filp)
{
	struct kvmppc_spapr_tce_table *stt = filp->private_data;
	struct kvmppc_spapr_tce_iommu_table *stit, *tmp;
	struct kvm *kvm = stt->kvm;

	mutex_lock(&kvm->lock);
	list_del_rcu(&stt->list);
	mutex_unlock(&kvm->lock);

	list_for_each_entry_safe(stit, tmp, &stt->iommu_tables, next) {
		WARN_ON(!kref_read(&stit->kref));
		while (1) {
			if (kref_put(&stit->kref, kvm_spapr_tce_liobn_put))
				break;
		}
	}

	kvm_put_kvm(stt->kvm);

	kvmppc_account_memlimit(
		kvmppc_stt_pages(kvmppc_tce_pages(stt->size)), false);
	call_rcu(&stt->rcu, release_spapr_tce_table);

	return 0;
}

static const struct file_operations kvm_spapr_tce_fops = {
	.mmap           = kvm_spapr_tce_mmap,
	.release	= kvm_spapr_tce_release,
};

long kvm_vm_ioctl_create_spapr_tce(struct kvm *kvm,
				   struct kvm_create_spapr_tce_64 *args)
{
	struct kvmppc_spapr_tce_table *stt = NULL;
	struct kvmppc_spapr_tce_table *siter;
	unsigned long npages, size = args->size;
	int ret = -ENOMEM;

	if (!args->size || args->page_shift < 12 || args->page_shift > 34 ||
		(args->offset + args->size > (ULLONG_MAX >> args->page_shift)))
		return -EINVAL;

	npages = kvmppc_tce_pages(size);
	ret = kvmppc_account_memlimit(kvmppc_stt_pages(npages), true);
	if (ret)
		return ret;

	ret = -ENOMEM;
	stt = kzalloc(sizeof(*stt) + npages * sizeof(struct page *),
		      GFP_KERNEL);
	if (!stt)
		goto fail_acct;

	stt->liobn = args->liobn;
	stt->page_shift = args->page_shift;
	stt->offset = args->offset;
	stt->size = size;
	stt->kvm = kvm;
	mutex_init(&stt->alloc_lock);
	INIT_LIST_HEAD_RCU(&stt->iommu_tables);

	mutex_lock(&kvm->lock);

	/* Check this LIOBN hasn't been previously allocated */
	ret = 0;
	list_for_each_entry(siter, &kvm->arch.spapr_tce_tables, list) {
		if (siter->liobn == args->liobn) {
			ret = -EBUSY;
			break;
		}
	}

	kvm_get_kvm(kvm);
	if (!ret)
		ret = anon_inode_getfd("kvm-spapr-tce", &kvm_spapr_tce_fops,
				       stt, O_RDWR | O_CLOEXEC);

	if (ret >= 0)
		list_add_rcu(&stt->list, &kvm->arch.spapr_tce_tables);
	else
		kvm_put_kvm(kvm);

	mutex_unlock(&kvm->lock);

	if (ret >= 0)
		return ret;

	kfree(stt);
 fail_acct:
	kvmppc_account_memlimit(kvmppc_stt_pages(npages), false);
	return ret;
}

static long kvmppc_tce_to_ua(struct kvm *kvm, unsigned long tce,
		unsigned long *ua)
{
	unsigned long gfn = tce >> PAGE_SHIFT;
	struct kvm_memory_slot *memslot;

	memslot = search_memslots(kvm_memslots(kvm), gfn);
	if (!memslot)
		return -EINVAL;

	*ua = __gfn_to_hva_memslot(memslot, gfn) |
		(tce & ~(PAGE_MASK | TCE_PCI_READ | TCE_PCI_WRITE));

	return 0;
}

static long kvmppc_tce_validate(struct kvmppc_spapr_tce_table *stt,
		unsigned long tce)
{
	unsigned long gpa = tce & ~(TCE_PCI_READ | TCE_PCI_WRITE);
	enum dma_data_direction dir = iommu_tce_direction(tce);
	struct kvmppc_spapr_tce_iommu_table *stit;
	unsigned long ua = 0;

	/* Allow userspace to poison TCE table */
	if (dir == DMA_NONE)
		return H_SUCCESS;

	if (iommu_tce_check_gpa(stt->page_shift, gpa))
		return H_TOO_HARD;

	if (kvmppc_tce_to_ua(stt->kvm, tce, &ua))
		return H_TOO_HARD;

	list_for_each_entry_rcu(stit, &stt->iommu_tables, next) {
		unsigned long hpa = 0;
		struct mm_iommu_table_group_mem_t *mem;
		long shift = stit->tbl->it_page_shift;

		mem = mm_iommu_lookup(stt->kvm->mm, ua, 1ULL << shift);
		if (!mem)
			return H_TOO_HARD;

		if (mm_iommu_ua_to_hpa(mem, ua, shift, &hpa))
			return H_TOO_HARD;
	}

	return H_SUCCESS;
}

/*
 * Handles TCE requests for emulated devices.
 * Puts guest TCE values to the table and expects user space to convert them.
 * Cannot fail so kvmppc_tce_validate must be called before it.
 */
static void kvmppc_tce_put(struct kvmppc_spapr_tce_table *stt,
		unsigned long idx, unsigned long tce)
{
	struct page *page;
	u64 *tbl;
	unsigned long sttpage;

	idx -= stt->offset;
	sttpage = idx / TCES_PER_PAGE;
	page = stt->pages[sttpage];

	if (!page) {
		/* We allow any TCE, not just with read|write permissions */
		if (!tce)
			return;

		page = kvm_spapr_get_tce_page(stt, sttpage);
		if (!page)
			return;
	}
	tbl = page_to_virt(page);

	tbl[idx % TCES_PER_PAGE] = tce;
}

static void kvmppc_clear_tce(struct mm_struct *mm, struct iommu_table *tbl,
		unsigned long entry)
{
	unsigned long hpa = 0;
	enum dma_data_direction dir = DMA_NONE;

	iommu_tce_xchg(mm, tbl, entry, &hpa, &dir);
}

static long kvmppc_tce_iommu_mapped_dec(struct kvm *kvm,
		struct iommu_table *tbl, unsigned long entry)
{
	struct mm_iommu_table_group_mem_t *mem = NULL;
	const unsigned long pgsize = 1ULL << tbl->it_page_shift;
	__be64 *pua = IOMMU_TABLE_USERSPACE_ENTRY_RO(tbl, entry);

	if (!pua)
		return H_SUCCESS;

	mem = mm_iommu_lookup(kvm->mm, be64_to_cpu(*pua), pgsize);
	if (!mem)
		return H_TOO_HARD;

	mm_iommu_mapped_dec(mem);

	*pua = cpu_to_be64(0);

	return H_SUCCESS;
}

static long kvmppc_tce_iommu_do_unmap(struct kvm *kvm,
		struct iommu_table *tbl, unsigned long entry)
{
	enum dma_data_direction dir = DMA_NONE;
	unsigned long hpa = 0;
	long ret;

	if (WARN_ON_ONCE(iommu_tce_xchg(kvm->mm, tbl, entry, &hpa, &dir)))
		return H_TOO_HARD;

	if (dir == DMA_NONE)
		return H_SUCCESS;

	ret = kvmppc_tce_iommu_mapped_dec(kvm, tbl, entry);
	if (ret != H_SUCCESS)
		iommu_tce_xchg(kvm->mm, tbl, entry, &hpa, &dir);

	return ret;
}

static long kvmppc_tce_iommu_unmap(struct kvm *kvm,
		struct kvmppc_spapr_tce_table *stt, struct iommu_table *tbl,
		unsigned long entry)
{
	unsigned long i, ret = H_SUCCESS;
	unsigned long subpages = 1ULL << (stt->page_shift - tbl->it_page_shift);
	unsigned long io_entry = entry * subpages;

	for (i = 0; i < subpages; ++i) {
		ret = kvmppc_tce_iommu_do_unmap(kvm, tbl, io_entry + i);
		if (ret != H_SUCCESS)
			break;
	}

	return ret;
}

long kvmppc_tce_iommu_do_map(struct kvm *kvm, struct iommu_table *tbl,
		unsigned long entry, unsigned long ua,
		enum dma_data_direction dir)
{
	long ret;
	unsigned long hpa;
	__be64 *pua = IOMMU_TABLE_USERSPACE_ENTRY(tbl, entry);
	struct mm_iommu_table_group_mem_t *mem;

	if (!pua)
		/* it_userspace allocation might be delayed */
		return H_TOO_HARD;

	mem = mm_iommu_lookup(kvm->mm, ua, 1ULL << tbl->it_page_shift);
	if (!mem)
		/* This only handles v2 IOMMU type, v1 is handled via ioctl() */
		return H_TOO_HARD;

	if (WARN_ON_ONCE(mm_iommu_ua_to_hpa(mem, ua, tbl->it_page_shift, &hpa)))
		return H_TOO_HARD;

	if (mm_iommu_mapped_inc(mem))
		return H_TOO_HARD;

	ret = iommu_tce_xchg(kvm->mm, tbl, entry, &hpa, &dir);
	if (WARN_ON_ONCE(ret)) {
		mm_iommu_mapped_dec(mem);
		return H_TOO_HARD;
	}

	if (dir != DMA_NONE)
		kvmppc_tce_iommu_mapped_dec(kvm, tbl, entry);

	*pua = cpu_to_be64(ua);

	return 0;
}

static long kvmppc_tce_iommu_map(struct kvm *kvm,
		struct kvmppc_spapr_tce_table *stt, struct iommu_table *tbl,
		unsigned long entry, unsigned long ua,
		enum dma_data_direction dir)
{
	unsigned long i, pgoff, ret = H_SUCCESS;
	unsigned long subpages = 1ULL << (stt->page_shift - tbl->it_page_shift);
	unsigned long io_entry = entry * subpages;

	for (i = 0, pgoff = 0; i < subpages;
			++i, pgoff += IOMMU_PAGE_SIZE(tbl)) {

		ret = kvmppc_tce_iommu_do_map(kvm, tbl,
				io_entry + i, ua + pgoff, dir);
		if (ret != H_SUCCESS)
			break;
	}

	return ret;
}

long kvmppc_h_put_tce(struct kvm_vcpu *vcpu, unsigned long liobn,
		      unsigned long ioba, unsigned long tce)
{
	struct kvmppc_spapr_tce_table *stt;
	long ret, idx;
	struct kvmppc_spapr_tce_iommu_table *stit;
	unsigned long entry, ua = 0;
	enum dma_data_direction dir;

	/* udbg_printf("H_PUT_TCE(): liobn=0x%lx ioba=0x%lx, tce=0x%lx\n", */
	/* 	    liobn, ioba, tce); */

	stt = kvmppc_find_table(vcpu->kvm, liobn);
	if (!stt)
		return H_TOO_HARD;

	ret = kvmppc_ioba_validate(stt, ioba, 1);
	if (ret != H_SUCCESS)
		return ret;

	idx = srcu_read_lock(&vcpu->kvm->srcu);

	ret = kvmppc_tce_validate(stt, tce);
	if (ret != H_SUCCESS)
		goto unlock_exit;

	dir = iommu_tce_direction(tce);

	if ((dir != DMA_NONE) && kvmppc_tce_to_ua(vcpu->kvm, tce, &ua)) {
		ret = H_PARAMETER;
		goto unlock_exit;
	}

	entry = ioba >> stt->page_shift;

	list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
		if (dir == DMA_NONE)
			ret = kvmppc_tce_iommu_unmap(vcpu->kvm, stt,
					stit->tbl, entry);
		else
			ret = kvmppc_tce_iommu_map(vcpu->kvm, stt, stit->tbl,
					entry, ua, dir);

		if (ret != H_SUCCESS) {
			kvmppc_clear_tce(vcpu->kvm->mm, stit->tbl, entry);
			goto unlock_exit;
		}
	}

	kvmppc_tce_put(stt, entry, tce);

unlock_exit:
	srcu_read_unlock(&vcpu->kvm->srcu, idx);

	return ret;
}
EXPORT_SYMBOL_GPL(kvmppc_h_put_tce);

long kvmppc_h_put_tce_indirect(struct kvm_vcpu *vcpu,
		unsigned long liobn, unsigned long ioba,
		unsigned long tce_list, unsigned long npages)
{
	struct kvmppc_spapr_tce_table *stt;
	long i, ret = H_SUCCESS, idx;
	unsigned long entry, ua = 0;
	u64 __user *tces;
	u64 tce;
	struct kvmppc_spapr_tce_iommu_table *stit;

	stt = kvmppc_find_table(vcpu->kvm, liobn);
	if (!stt)
		return H_TOO_HARD;

	entry = ioba >> stt->page_shift;
	/*
	 * SPAPR spec says that the maximum size of the list is 512 TCEs
	 * so the whole table fits in 4K page
	 */
	if (npages > 512)
		return H_PARAMETER;

	if (tce_list & (SZ_4K - 1))
		return H_PARAMETER;

	ret = kvmppc_ioba_validate(stt, ioba, npages);
	if (ret != H_SUCCESS)
		return ret;

	idx = srcu_read_lock(&vcpu->kvm->srcu);
	if (kvmppc_tce_to_ua(vcpu->kvm, tce_list, &ua)) {
		ret = H_TOO_HARD;
		goto unlock_exit;
	}
	tces = (u64 __user *) ua;

	for (i = 0; i < npages; ++i) {
		if (get_user(tce, tces + i)) {
			ret = H_TOO_HARD;
			goto unlock_exit;
		}
		tce = be64_to_cpu(tce);

		ret = kvmppc_tce_validate(stt, tce);
		if (ret != H_SUCCESS)
			goto unlock_exit;
	}

	for (i = 0; i < npages; ++i) {
		/*
		 * This looks unsafe, because we validate, then regrab
		 * the TCE from userspace which could have been changed by
		 * another thread.
		 *
		 * But it actually is safe, because the relevant checks will be
		 * re-executed in the following code.  If userspace tries to
		 * change this dodgily it will result in a messier failure mode
		 * but won't threaten the host.
		 */
		if (get_user(tce, tces + i)) {
			ret = H_TOO_HARD;
			goto unlock_exit;
		}
		tce = be64_to_cpu(tce);

		if (kvmppc_tce_to_ua(vcpu->kvm, tce, &ua))
			return H_PARAMETER;

		list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
			ret = kvmppc_tce_iommu_map(vcpu->kvm, stt,
					stit->tbl, entry + i, ua,
					iommu_tce_direction(tce));

			if (ret != H_SUCCESS) {
				kvmppc_clear_tce(vcpu->kvm->mm, stit->tbl,
						entry);
				goto unlock_exit;
			}
		}

		kvmppc_tce_put(stt, entry + i, tce);
	}

unlock_exit:
	srcu_read_unlock(&vcpu->kvm->srcu, idx);

	return ret;
}
EXPORT_SYMBOL_GPL(kvmppc_h_put_tce_indirect);

long kvmppc_h_stuff_tce(struct kvm_vcpu *vcpu,
		unsigned long liobn, unsigned long ioba,
		unsigned long tce_value, unsigned long npages)
{
	struct kvmppc_spapr_tce_table *stt;
	long i, ret;
	struct kvmppc_spapr_tce_iommu_table *stit;

	stt = kvmppc_find_table(vcpu->kvm, liobn);
	if (!stt)
		return H_TOO_HARD;

	ret = kvmppc_ioba_validate(stt, ioba, npages);
	if (ret != H_SUCCESS)
		return ret;

	/* Check permission bits only to allow userspace poison TCE for debug */
	if (tce_value & (TCE_PCI_WRITE | TCE_PCI_READ))
		return H_PARAMETER;

	list_for_each_entry_lockless(stit, &stt->iommu_tables, next) {
		unsigned long entry = ioba >> stt->page_shift;

		for (i = 0; i < npages; ++i) {
			ret = kvmppc_tce_iommu_unmap(vcpu->kvm, stt,
					stit->tbl, entry + i);

			if (ret == H_SUCCESS)
				continue;

			if (ret == H_TOO_HARD)
				return ret;

			WARN_ON_ONCE(1);
			kvmppc_clear_tce(vcpu->kvm->mm, stit->tbl, entry);
		}
	}

	for (i = 0; i < npages; ++i, ioba += (1ULL << stt->page_shift))
		kvmppc_tce_put(stt, ioba >> stt->page_shift, tce_value);

	return H_SUCCESS;
}
EXPORT_SYMBOL_GPL(kvmppc_h_stuff_tce);