vfio: Provide module option to disable vfio_iommu_type1 hugepage support

[deliverable/linux.git] / drivers / vfio / vfio_iommu_type1.c

/*
 * VFIO: IOMMU DMA mapping support for Type1 IOMMU
 *
 * Copyright (C) 2012 Red Hat, Inc.  All rights reserved.
 *     Author: Alex Williamson <alex.williamson@redhat.com>
 *
 * 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.
 *
 * Derived from original vfio:
 * Copyright 2010 Cisco Systems, Inc.  All rights reserved.
 * Author: Tom Lyon, pugs@cisco.com
 *
 * We arbitrarily define a Type1 IOMMU as one matching the below code.
 * It could be called the x86 IOMMU as it's designed for AMD-Vi & Intel
 * VT-d, but that makes it harder to re-use as theoretically anyone
 * implementing a similar IOMMU could make use of this.  We expect the
 * IOMMU to support the IOMMU API and have few to no restrictions around
 * the IOVA range that can be mapped.  The Type1 IOMMU is currently
 * optimized for relatively static mappings of a userspace process with
 * userpsace pages pinned into memory.  We also assume devices and IOMMU
 * domains are PCI based as the IOMMU API is still centered around a
 * device/bus interface rather than a group interface.
 */

#include <linux/compat.h>
#include <linux/device.h>
#include <linux/fs.h>
#include <linux/iommu.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/pci.h>          /* pci_bus_type */
#include <linux/rbtree.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/uaccess.h>
#include <linux/vfio.h>
#include <linux/workqueue.h>

#define DRIVER_VERSION  "0.2"
#define DRIVER_AUTHOR   "Alex Williamson <alex.williamson@redhat.com>"
#define DRIVER_DESC     "Type1 IOMMU driver for VFIO"

static bool allow_unsafe_interrupts;
module_param_named(allow_unsafe_interrupts,
                   allow_unsafe_interrupts, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(allow_unsafe_interrupts,
                 "Enable VFIO IOMMU support for on platforms without interrupt remapping support.");

static bool disable_hugepages;
module_param_named(disable_hugepages,
                   disable_hugepages, bool, S_IRUGO | S_IWUSR);
MODULE_PARM_DESC(disable_hugepages,
                 "Disable VFIO IOMMU support for IOMMU hugepages.");

struct vfio_iommu {
        struct iommu_domain     *domain;
        struct mutex            lock;
        struct rb_root          dma_list;
        struct list_head        group_list;
        bool                    cache;
};

struct vfio_dma {
        struct rb_node          node;
        dma_addr_t              iova;           /* Device address */
        unsigned long           vaddr;          /* Process virtual addr */
        size_t                  size;           /* Map size (bytes) */
        int                     prot;           /* IOMMU_READ/WRITE */
};

struct vfio_group {
        struct iommu_group      *iommu_group;
        struct list_head        next;
};

/*
 * This code handles mapping and unmapping of user data buffers
 * into DMA'ble space using the IOMMU
 */

static struct vfio_dma *vfio_find_dma(struct vfio_iommu *iommu,
                                      dma_addr_t start, size_t size)
{
        struct rb_node *node = iommu->dma_list.rb_node;

        while (node) {
                struct vfio_dma *dma = rb_entry(node, struct vfio_dma, node);

                if (start + size <= dma->iova)
                        node = node->rb_left;
                else if (start >= dma->iova + dma->size)
                        node = node->rb_right;
                else
                        return dma;
        }

        return NULL;
}

static void vfio_insert_dma(struct vfio_iommu *iommu, struct vfio_dma *new)
{
        struct rb_node **link = &iommu->dma_list.rb_node, *parent = NULL;
        struct vfio_dma *dma;

        while (*link) {
                parent = *link;
                dma = rb_entry(parent, struct vfio_dma, node);

                if (new->iova + new->size <= dma->iova)
                        link = &(*link)->rb_left;
                else
                        link = &(*link)->rb_right;
        }

        rb_link_node(&new->node, parent, link);
        rb_insert_color(&new->node, &iommu->dma_list);
}

static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *old)
{
        rb_erase(&old->node, &iommu->dma_list);
}

struct vwork {
        struct mm_struct        *mm;
        long                    npage;
        struct work_struct      work;
};

/* delayed decrement/increment for locked_vm */
static void vfio_lock_acct_bg(struct work_struct *work)
{
        struct vwork *vwork = container_of(work, struct vwork, work);
        struct mm_struct *mm;

        mm = vwork->mm;
        down_write(&mm->mmap_sem);
        mm->locked_vm += vwork->npage;
        up_write(&mm->mmap_sem);
        mmput(mm);
        kfree(vwork);
}

static void vfio_lock_acct(long npage)
{
        struct vwork *vwork;
        struct mm_struct *mm;

        if (!current->mm || !npage)
                return; /* process exited or nothing to do */

        if (down_write_trylock(&current->mm->mmap_sem)) {
                current->mm->locked_vm += npage;
                up_write(&current->mm->mmap_sem);
                return;
        }

        /*
         * Couldn't get mmap_sem lock, so must setup to update
         * mm->locked_vm later. If locked_vm were atomic, we
         * wouldn't need this silliness
         */
        vwork = kmalloc(sizeof(struct vwork), GFP_KERNEL);
        if (!vwork)
                return;
        mm = get_task_mm(current);
        if (!mm) {
                kfree(vwork);
                return;
        }
        INIT_WORK(&vwork->work, vfio_lock_acct_bg);
        vwork->mm = mm;
        vwork->npage = npage;
        schedule_work(&vwork->work);
}

/*
 * Some mappings aren't backed by a struct page, for example an mmap'd
 * MMIO range for our own or another device.  These use a different
 * pfn conversion and shouldn't be tracked as locked pages.
 */
static bool is_invalid_reserved_pfn(unsigned long pfn)
{
        if (pfn_valid(pfn)) {
                bool reserved;
                struct page *tail = pfn_to_page(pfn);
                struct page *head = compound_trans_head(tail);
                reserved = !!(PageReserved(head));
                if (head != tail) {
                        /*
                         * "head" is not a dangling pointer
                         * (compound_trans_head takes care of that)
                         * but the hugepage may have been split
                         * from under us (and we may not hold a
                         * reference count on the head page so it can
                         * be reused before we run PageReferenced), so
                         * we've to check PageTail before returning
                         * what we just read.
                         */
                        smp_rmb();
                        if (PageTail(tail))
                                return reserved;
                }
                return PageReserved(tail);
        }

        return true;
}

static int put_pfn(unsigned long pfn, int prot)
{
        if (!is_invalid_reserved_pfn(pfn)) {
                struct page *page = pfn_to_page(pfn);
                if (prot & IOMMU_WRITE)
                        SetPageDirty(page);
                put_page(page);
                return 1;
        }
        return 0;
}

static int vaddr_get_pfn(unsigned long vaddr, int prot, unsigned long *pfn)
{
        struct page *page[1];
        struct vm_area_struct *vma;
        int ret = -EFAULT;

        if (get_user_pages_fast(vaddr, 1, !!(prot & IOMMU_WRITE), page) == 1) {
                *pfn = page_to_pfn(page[0]);
                return 0;
        }

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

        vma = find_vma_intersection(current->mm, vaddr, vaddr + 1);

        if (vma && vma->vm_flags & VM_PFNMAP) {
                *pfn = ((vaddr - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff;
                if (is_invalid_reserved_pfn(*pfn))
                        ret = 0;
        }

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

        return ret;
}

/*
 * Attempt to pin pages.  We really don't want to track all the pfns and
 * the iommu can only map chunks of consecutive pfns anyway, so get the
 * first page and all consecutive pages with the same locking.
 */
static long vfio_pin_pages(unsigned long vaddr, long npage,
                           int prot, unsigned long *pfn_base)
{
        unsigned long limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
        bool lock_cap = capable(CAP_IPC_LOCK);
        long ret, i;

        if (!current->mm)
                return -ENODEV;

        ret = vaddr_get_pfn(vaddr, prot, pfn_base);
        if (ret)
                return ret;

        if (is_invalid_reserved_pfn(*pfn_base))
                return 1;

        if (!lock_cap && current->mm->locked_vm + 1 > limit) {
                put_pfn(*pfn_base, prot);
                pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n", __func__,
                        limit << PAGE_SHIFT);
                return -ENOMEM;
        }

        if (unlikely(disable_hugepages)) {
                vfio_lock_acct(1);
                return 1;
        }

        /* Lock all the consecutive pages from pfn_base */
        for (i = 1, vaddr += PAGE_SIZE; i < npage; i++, vaddr += PAGE_SIZE) {
                unsigned long pfn = 0;

                ret = vaddr_get_pfn(vaddr, prot, &pfn);
                if (ret)
                        break;

                if (pfn != *pfn_base + i || is_invalid_reserved_pfn(pfn)) {
                        put_pfn(pfn, prot);
                        break;
                }

                if (!lock_cap && current->mm->locked_vm + i + 1 > limit) {
                        put_pfn(pfn, prot);
                        pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n",
                                __func__, limit << PAGE_SHIFT);
                        break;
                }
        }

        vfio_lock_acct(i);

        return i;
}

static long vfio_unpin_pages(unsigned long pfn, long npage,
                             int prot, bool do_accounting)
{
        unsigned long unlocked = 0;
        long i;

        for (i = 0; i < npage; i++)
                unlocked += put_pfn(pfn++, prot);

        if (do_accounting)
                vfio_lock_acct(-unlocked);

        return unlocked;
}

static int vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma,
                            dma_addr_t iova, size_t *size)
{
        dma_addr_t start = iova, end = iova + *size;
        long unlocked = 0;

        while (iova < end) {
                size_t unmapped;
                phys_addr_t phys;

                /*
                 * We use the IOMMU to track the physical address.  This
                 * saves us from having a lot more entries in our mapping
                 * tree.  The downside is that we don't track the size
                 * used to do the mapping.  We request unmap of a single
                 * page, but expect IOMMUs that support large pages to
                 * unmap a larger chunk.
                 */
                phys = iommu_iova_to_phys(iommu->domain, iova);
                if (WARN_ON(!phys)) {
                        iova += PAGE_SIZE;
                        continue;
                }

                unmapped = iommu_unmap(iommu->domain, iova, PAGE_SIZE);
                if (!unmapped)
                        break;

                unlocked += vfio_unpin_pages(phys >> PAGE_SHIFT,
                                             unmapped >> PAGE_SHIFT,
                                             dma->prot, false);
                iova += unmapped;
        }

        vfio_lock_acct(-unlocked);

        *size = iova - start;

        return 0;
}

static int vfio_remove_dma_overlap(struct vfio_iommu *iommu, dma_addr_t start,
                                   size_t *size, struct vfio_dma *dma)
{
        size_t offset, overlap, tmp;
        struct vfio_dma *split;
        int ret;

        /*
         * Existing dma region is completely covered, unmap all.  This is
         * the likely case since userspace tends to map and unmap buffers
         * in one shot rather than multiple mappings within a buffer.
         */
        if (likely(start <= dma->iova &&
                   start + *size >= dma->iova + dma->size)) {
                *size = dma->size;
                ret = vfio_unmap_unpin(iommu, dma, dma->iova, size);
                if (ret)
                        return ret;

                /*
                 * Did we remove more than we have?  Should never happen
                 * since a vfio_dma is contiguous in iova and vaddr.
                 */
                WARN_ON(*size != dma->size);

                vfio_remove_dma(iommu, dma);
                kfree(dma);
                return 0;
        }

        /* Overlap low address of existing range */
        if (start <= dma->iova) {
                overlap = start + *size - dma->iova;
                ret = vfio_unmap_unpin(iommu, dma, dma->iova, &overlap);
                if (ret)
                        return ret;

                vfio_remove_dma(iommu, dma);

                /*
                 * Check, we may have removed to whole vfio_dma.  If not
                 * fixup and re-insert.
                 */
                if (overlap < dma->size) {
                        dma->iova += overlap;
                        dma->vaddr += overlap;
                        dma->size -= overlap;
                        vfio_insert_dma(iommu, dma);
                }
                *size = overlap;
                return 0;
        }

        /* Overlap high address of existing range */
        if (start + *size >= dma->iova + dma->size) {
                offset = start - dma->iova;
                overlap = dma->size - offset;

                ret = vfio_unmap_unpin(iommu, dma, start, &overlap);
                if (ret)
                        return ret;

                /*
                 * We may have unmapped the entire vfio_dma if the user is
                 * trying to unmap a sub-region of what was originally
                 * mapped.  If anything left, we can resize in place since
                 * iova is unchanged.
                 */
                if (overlap < dma->size)
                        dma->size -= overlap;
                else
                        vfio_remove_dma(iommu, dma);

                *size = overlap;
                return 0;
        }

        /* Split existing */
        offset = start - dma->iova;

        ret = vfio_unmap_unpin(iommu, dma, start, size);
        if (ret)
                return ret;

        WARN_ON(!*size);
        tmp = dma->size;

        /*
         * Resize the lower vfio_dma in place, insert new for remaining
         * upper segment.
         */
        dma->size = offset;

        if (offset + *size < tmp) {
                split = kzalloc(sizeof(*split), GFP_KERNEL);
                if (!split)
                        return -ENOMEM;

                split->size = tmp - offset - *size;
                split->iova = dma->iova + offset + *size;
                split->vaddr = dma->vaddr + offset + *size;
                split->prot = dma->prot;
                vfio_insert_dma(iommu, split);
        }

        return 0;
}

static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
                             struct vfio_iommu_type1_dma_unmap *unmap)
{
        uint64_t mask;
        struct vfio_dma *dma;
        size_t unmapped = 0, size;
        int ret = 0;

        mask = ((uint64_t)1 << __ffs(iommu->domain->ops->pgsize_bitmap)) - 1;

        if (unmap->iova & mask)
                return -EINVAL;
        if (unmap->size & mask)
                return -EINVAL;

        WARN_ON(mask & PAGE_MASK);

        mutex_lock(&iommu->lock);

        while ((dma = vfio_find_dma(iommu, unmap->iova, unmap->size))) {
                size = unmap->size;
                ret = vfio_remove_dma_overlap(iommu, unmap->iova, &size, dma);
                if (ret)
                        break;
                unmapped += size;
        }

        mutex_unlock(&iommu->lock);

        /*
         * We may unmap more than requested, update the unmap struct so
         * userspace can know.
         */
        unmap->size = unmapped;

        return ret;
}

/*
 * Turns out AMD IOMMU has a page table bug where it won't map large pages
 * to a region that previously mapped smaller pages.  This should be fixed
 * soon, so this is just a temporary workaround to break mappings down into
 * PAGE_SIZE.  Better to map smaller pages than nothing.
 */
static int map_try_harder(struct vfio_iommu *iommu, dma_addr_t iova,
                          unsigned long pfn, long npage, int prot)
{
        long i;
        int ret;

        for (i = 0; i < npage; i++, pfn++, iova += PAGE_SIZE) {
                ret = iommu_map(iommu->domain, iova,
                                (phys_addr_t)pfn << PAGE_SHIFT,
                                PAGE_SIZE, prot);
                if (ret)
                        break;
        }

        for (; i < npage && i > 0; i--, iova -= PAGE_SIZE)
                iommu_unmap(iommu->domain, iova, PAGE_SIZE);

        return ret;
}

static int vfio_dma_do_map(struct vfio_iommu *iommu,
                           struct vfio_iommu_type1_dma_map *map)
{
        dma_addr_t end, iova;
        unsigned long vaddr = map->vaddr;
        size_t size = map->size;
        long npage;
        int ret = 0, prot = 0;
        uint64_t mask;

        end = map->iova + map->size;

        mask = ((uint64_t)1 << __ffs(iommu->domain->ops->pgsize_bitmap)) - 1;

        /* READ/WRITE from device perspective */
        if (map->flags & VFIO_DMA_MAP_FLAG_WRITE)
                prot |= IOMMU_WRITE;
        if (map->flags & VFIO_DMA_MAP_FLAG_READ)
                prot |= IOMMU_READ;

        if (!prot)
                return -EINVAL; /* No READ/WRITE? */

        if (iommu->cache)
                prot |= IOMMU_CACHE;

        if (vaddr & mask)
                return -EINVAL;
        if (map->iova & mask)
                return -EINVAL;
        if (!map->size || map->size & mask)
                return -EINVAL;

        WARN_ON(mask & PAGE_MASK);

        /* Don't allow IOVA wrap */
        if (end && end < map->iova)
                return -EINVAL;

        /* Don't allow virtual address wrap */
        if (vaddr + map->size && vaddr + map->size < vaddr)
                return -EINVAL;

        mutex_lock(&iommu->lock);

        if (vfio_find_dma(iommu, map->iova, map->size)) {
                mutex_unlock(&iommu->lock);
                return -EEXIST;
        }

        for (iova = map->iova; iova < end; iova += size, vaddr += size) {
                struct vfio_dma *dma = NULL;
                unsigned long pfn;
                long i;

                /* Pin a contiguous chunk of memory */
                npage = vfio_pin_pages(vaddr, (end - iova) >> PAGE_SHIFT,
                                       prot, &pfn);
                if (npage <= 0) {
                        WARN_ON(!npage);
                        ret = (int)npage;
                        break;
                }

                /* Verify pages are not already mapped */
                for (i = 0; i < npage; i++) {
                        if (iommu_iova_to_phys(iommu->domain,
                                               iova + (i << PAGE_SHIFT))) {
                                vfio_unpin_pages(pfn, npage, prot, true);
                                ret = -EBUSY;
                                break;
                        }
                }

                ret = iommu_map(iommu->domain, iova,
                                (phys_addr_t)pfn << PAGE_SHIFT,
                                npage << PAGE_SHIFT, prot);
                if (ret) {
                        if (ret != -EBUSY ||
                            map_try_harder(iommu, iova, pfn, npage, prot)) {
                                vfio_unpin_pages(pfn, npage, prot, true);
                                break;
                        }
                }

                size = npage << PAGE_SHIFT;

                /*
                 * Check if we abut a region below - nothing below 0.
                 * This is the most likely case when mapping chunks of
                 * physically contiguous regions within a virtual address
                 * range.  Update the abutting entry in place since iova
                 * doesn't change.
                 */
                if (likely(iova)) {
                        struct vfio_dma *tmp;
                        tmp = vfio_find_dma(iommu, iova - 1, 1);
                        if (tmp && tmp->prot == prot &&
                            tmp->vaddr + tmp->size == vaddr) {
                                tmp->size += size;

                                iova = tmp->iova;
                                size = tmp->size;
                                vaddr = tmp->vaddr;
                                dma = tmp;
                        }
                }

                /* Check if we abut a region above - nothing above ~0 + 1 */
                if (likely(iova + size)) {
                        struct vfio_dma *tmp;

                        tmp = vfio_find_dma(iommu, iova + size, 1);
                        if (tmp && tmp->prot == prot &&
                            tmp->vaddr == vaddr + size) {
                                vfio_remove_dma(iommu, tmp);
                                if (dma)
                                        dma->size += tmp->size;
                                else
                                        size += tmp->size;
                                kfree(tmp);
                        }
                }

                if (!dma) {
                        dma = kzalloc(sizeof(*dma), GFP_KERNEL);
                        if (!dma) {
                                iommu_unmap(iommu->domain, iova, size);
                                vfio_unpin_pages(pfn, npage, prot, true);
                                ret = -ENOMEM;
                                break;
                        }

                        dma->size = size;
                        dma->iova = iova;
                        dma->vaddr = vaddr;
                        dma->prot = prot;
                        vfio_insert_dma(iommu, dma);
                }
        }

        if (ret) {
                struct vfio_dma *tmp;
                iova = map->iova;
                size = map->size;
                while ((tmp = vfio_find_dma(iommu, iova, size))) {
                        if (vfio_remove_dma_overlap(iommu, iova, &size, tmp)) {
                                pr_warn("%s: Error rolling back failed map\n",
                                        __func__);
                                break;
                        }
                }
        }

        mutex_unlock(&iommu->lock);
        return ret;
}

static int vfio_iommu_type1_attach_group(void *iommu_data,
                                         struct iommu_group *iommu_group)
{
        struct vfio_iommu *iommu = iommu_data;
        struct vfio_group *group, *tmp;
        int ret;

        group = kzalloc(sizeof(*group), GFP_KERNEL);
        if (!group)
                return -ENOMEM;

        mutex_lock(&iommu->lock);

        list_for_each_entry(tmp, &iommu->group_list, next) {
                if (tmp->iommu_group == iommu_group) {
                        mutex_unlock(&iommu->lock);
                        kfree(group);
                        return -EINVAL;
                }
        }

        /*
         * TODO: Domain have capabilities that might change as we add
         * groups (see iommu->cache, currently never set).  Check for
         * them and potentially disallow groups to be attached when it
         * would change capabilities (ugh).
         */
        ret = iommu_attach_group(iommu->domain, iommu_group);
        if (ret) {
                mutex_unlock(&iommu->lock);
                kfree(group);
                return ret;
        }

        group->iommu_group = iommu_group;
        list_add(&group->next, &iommu->group_list);

        mutex_unlock(&iommu->lock);

        return 0;
}

static void vfio_iommu_type1_detach_group(void *iommu_data,
                                          struct iommu_group *iommu_group)
{
        struct vfio_iommu *iommu = iommu_data;
        struct vfio_group *group;

        mutex_lock(&iommu->lock);

        list_for_each_entry(group, &iommu->group_list, next) {
                if (group->iommu_group == iommu_group) {
                        iommu_detach_group(iommu->domain, iommu_group);
                        list_del(&group->next);
                        kfree(group);
                        break;
                }
        }

        mutex_unlock(&iommu->lock);
}

static void *vfio_iommu_type1_open(unsigned long arg)
{
        struct vfio_iommu *iommu;

        if (arg != VFIO_TYPE1_IOMMU)
                return ERR_PTR(-EINVAL);

        iommu = kzalloc(sizeof(*iommu), GFP_KERNEL);
        if (!iommu)
                return ERR_PTR(-ENOMEM);

        INIT_LIST_HEAD(&iommu->group_list);
        iommu->dma_list = RB_ROOT;
        mutex_init(&iommu->lock);

        /*
         * Wish we didn't have to know about bus_type here.
         */
        iommu->domain = iommu_domain_alloc(&pci_bus_type);
        if (!iommu->domain) {
                kfree(iommu);
                return ERR_PTR(-EIO);
        }

        /*
         * Wish we could specify required capabilities rather than create
         * a domain, see what comes out and hope it doesn't change along
         * the way.  Fortunately we know interrupt remapping is global for
         * our iommus.
         */
        if (!allow_unsafe_interrupts &&
            !iommu_domain_has_cap(iommu->domain, IOMMU_CAP_INTR_REMAP)) {
                pr_warn("%s: No interrupt remapping support.  Use the module param \"allow_unsafe_interrupts\" to enable VFIO IOMMU support on this platform\n",
                       __func__);
                iommu_domain_free(iommu->domain);
                kfree(iommu);
                return ERR_PTR(-EPERM);
        }

        return iommu;
}

static void vfio_iommu_type1_release(void *iommu_data)
{
        struct vfio_iommu *iommu = iommu_data;
        struct vfio_group *group, *group_tmp;
        struct rb_node *node;

        list_for_each_entry_safe(group, group_tmp, &iommu->group_list, next) {
                iommu_detach_group(iommu->domain, group->iommu_group);
                list_del(&group->next);
                kfree(group);
        }

        while ((node = rb_first(&iommu->dma_list))) {
                struct vfio_dma *dma = rb_entry(node, struct vfio_dma, node);
                size_t size = dma->size;
                vfio_remove_dma_overlap(iommu, dma->iova, &size, dma);
        }

        iommu_domain_free(iommu->domain);
        iommu->domain = NULL;
        kfree(iommu);
}

static long vfio_iommu_type1_ioctl(void *iommu_data,
                                   unsigned int cmd, unsigned long arg)
{
        struct vfio_iommu *iommu = iommu_data;
        unsigned long minsz;

        if (cmd == VFIO_CHECK_EXTENSION) {
                switch (arg) {
                case VFIO_TYPE1_IOMMU:
                        return 1;
                default:
                        return 0;
                }
        } else if (cmd == VFIO_IOMMU_GET_INFO) {
                struct vfio_iommu_type1_info info;

                minsz = offsetofend(struct vfio_iommu_type1_info, iova_pgsizes);

                if (copy_from_user(&info, (void __user *)arg, minsz))
                        return -EFAULT;

                if (info.argsz < minsz)
                        return -EINVAL;

                info.flags = 0;

                info.iova_pgsizes = iommu->domain->ops->pgsize_bitmap;

                return copy_to_user((void __user *)arg, &info, minsz);

        } else if (cmd == VFIO_IOMMU_MAP_DMA) {
                struct vfio_iommu_type1_dma_map map;
                uint32_t mask = VFIO_DMA_MAP_FLAG_READ |
                                VFIO_DMA_MAP_FLAG_WRITE;

                minsz = offsetofend(struct vfio_iommu_type1_dma_map, size);

                if (copy_from_user(&map, (void __user *)arg, minsz))
                        return -EFAULT;

                if (map.argsz < minsz || map.flags & ~mask)
                        return -EINVAL;

                return vfio_dma_do_map(iommu, &map);

        } else if (cmd == VFIO_IOMMU_UNMAP_DMA) {
                struct vfio_iommu_type1_dma_unmap unmap;
                long ret;

                minsz = offsetofend(struct vfio_iommu_type1_dma_unmap, size);

                if (copy_from_user(&unmap, (void __user *)arg, minsz))
                        return -EFAULT;

                if (unmap.argsz < minsz || unmap.flags)
                        return -EINVAL;

                ret = vfio_dma_do_unmap(iommu, &unmap);
                if (ret)
                        return ret;

                return copy_to_user((void __user *)arg, &unmap, minsz);
        }

        return -ENOTTY;
}

static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
        .name           = "vfio-iommu-type1",
        .owner          = THIS_MODULE,
        .open           = vfio_iommu_type1_open,
        .release        = vfio_iommu_type1_release,
        .ioctl          = vfio_iommu_type1_ioctl,
        .attach_group   = vfio_iommu_type1_attach_group,
        .detach_group   = vfio_iommu_type1_detach_group,
};

static int __init vfio_iommu_type1_init(void)
{
        if (!iommu_present(&pci_bus_type))
                return -ENODEV;

        return vfio_register_iommu_driver(&vfio_iommu_driver_ops_type1);
}

static void __exit vfio_iommu_type1_cleanup(void)
{
        vfio_unregister_iommu_driver(&vfio_iommu_driver_ops_type1);
}

module_init(vfio_iommu_type1_init);
module_exit(vfio_iommu_type1_cleanup);

MODULE_VERSION(DRIVER_VERSION);
MODULE_LICENSE("GPL v2");
MODULE_AUTHOR(DRIVER_AUTHOR);
MODULE_DESCRIPTION(DRIVER_DESC);