[Qemu-devel] [PATCH v2 4/5] vfio: VFIO core IOMMU mapping support

[Alex Williamson]

Backing for operations on the IOMMU object, including DMA
mapping and unmapping.

Signed-off-by: Alex Williamson <address@hidden>
---

 drivers/vfio/vfio_iommu.c |  611 +++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 611 insertions(+), 0 deletions(-)
 create mode 100644 drivers/vfio/vfio_iommu.c

diff --git a/drivers/vfio/vfio_iommu.c b/drivers/vfio/vfio_iommu.c
new file mode 100644
index 0000000..49e6b2d
--- /dev/null
+++ b/drivers/vfio/vfio_iommu.c
@@ -0,0 +1,611 @@
+/*
+ * VFIO: IOMMU DMA mapping support
+ *
+ * Copyright (C) 2012 Red Hat, Inc.  All rights reserved.
+ *     Author: Alex Williamson <address@hidden>
+ *
+ * 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, address@hidden
+ */
+
+#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/sched.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+#include <linux/vfio.h>
+#include <linux/workqueue.h>
+
+#include "vfio_private.h"
+
+struct vfio_dma_map_entry {
+       struct list_head        list;
+       dma_addr_t              iova;           /* Device address */
+       unsigned long           vaddr;          /* Process virtual addr */
+       long                    npage;          /* Number of pages */
+       int                     prot;           /* IOMMU_READ/WRITE */
+};
+
+/*
+ * This code handles mapping and unmapping of user data buffers
+ * into DMA'ble space using the IOMMU
+ */
+
+#define NPAGE_TO_SIZE(npage)   ((size_t)(npage) << PAGE_SHIFT)
+
+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)
+               return; /* process exited */
+
+       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;
+}
+
+/* Unmap DMA region */
+static long __vfio_dma_do_unmap(struct vfio_iommu *iommu, dma_addr_t iova,
+                            long npage, int prot)
+{
+       long i, unlocked = 0;
+
+       for (i = 0; i < npage; i++, iova += PAGE_SIZE) {
+               unsigned long pfn;
+
+               pfn = iommu_iova_to_phys(iommu->domain, iova) >> PAGE_SHIFT;
+               if (pfn) {
+                       iommu_unmap(iommu->domain, iova, PAGE_SIZE);
+                       unlocked += put_pfn(pfn, prot);
+               }
+       }
+       return unlocked;
+}
+
+static void vfio_dma_unmap(struct vfio_iommu *iommu, dma_addr_t iova,
+                          long npage, int prot)
+{
+       long unlocked;
+
+       unlocked = __vfio_dma_do_unmap(iommu, iova, npage, prot);
+       vfio_lock_acct(-unlocked);
+}
+
+/* Unmap ALL DMA regions */
+void vfio_iommu_unmapall(struct vfio_iommu *iommu)
+{
+       struct list_head *pos, *tmp;
+
+       mutex_lock(&iommu->lock);
+       list_for_each_safe(pos, tmp, &iommu->dma_list) {
+               struct vfio_dma_map_entry *dma;
+
+               dma = list_entry(pos, struct vfio_dma_map_entry, list);
+               vfio_dma_unmap(iommu, dma->iova, dma->npage, dma->prot);
+               list_del(&dma->list);
+               kfree(dma);
+       }
+       mutex_unlock(&iommu->lock);
+}
+
+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;
+}
+
+/* Map DMA region */
+static int __vfio_dma_map(struct vfio_iommu *iommu, dma_addr_t iova,
+                         unsigned long vaddr, long npage, int prot)
+{
+       dma_addr_t start = iova;
+       long i, locked = 0;
+       int ret;
+
+       /* Verify that pages are not already mapped */
+       for (i = 0; i < npage; i++, iova += PAGE_SIZE)
+               if (iommu_iova_to_phys(iommu->domain, iova))
+                       return -EBUSY;
+
+       iova = start;
+
+       if (iommu->cache)
+               prot |= IOMMU_CACHE;
+
+       /*
+        * XXX We break mappings into pages and use get_user_pages_fast to
+        * pin the pages in memory.  It's been suggested that mlock might
+        * provide a more efficient mechanism, but nothing prevents the
+        * user from munlocking the pages, which could then allow the user
+        * access to random host memory.  We also have no guarantee from the
+        * IOMMU API that the iommu driver can unmap sub-pages of previous
+        * mappings.  This means we might lose an entire range if a single
+        * page within it is unmapped.  Single page mappings are inefficient,
+        * but provide the most flexibility for now.
+        */
+       for (i = 0; i < npage; i++, iova += PAGE_SIZE, vaddr += PAGE_SIZE) {
+               unsigned long pfn = 0;
+
+               ret = vaddr_get_pfn(vaddr, prot, &pfn);
+               if (ret) {
+                       __vfio_dma_do_unmap(iommu, start, i, prot);
+                       return ret;
+               }
+
+               /*
+                * Only add actual locked pages to accounting
+                * XXX We're effectively marking a page locked for every
+                * IOVA page even though it's possible the user could be
+                * backing multiple IOVAs with the same vaddr.  This over-
+                * penalizes the user process, but we currently have no
+                * easy way to do this properly.
+                */
+               if (!is_invalid_reserved_pfn(pfn))
+                       locked++;
+
+               ret = iommu_map(iommu->domain, iova,
+                               (phys_addr_t)pfn << PAGE_SHIFT,
+                               PAGE_SIZE, prot);
+               if (ret) {
+                       /* Back out mappings on error */
+                       put_pfn(pfn, prot);
+                       __vfio_dma_do_unmap(iommu, start, i, prot);
+                       return ret;
+               }
+       }
+       vfio_lock_acct(locked);
+       return 0;
+}
+
+static inline bool ranges_overlap(dma_addr_t start1, size_t size1,
+                                 dma_addr_t start2, size_t size2)
+{
+       if (start1 < start2)
+               return (start2 - start1 < size1);
+       else if (start2 < start1)
+               return (start1 - start2 < size2);
+       return (size1 > 0 && size2 > 0);
+}
+
+static struct vfio_dma_map_entry *vfio_find_dma(struct vfio_iommu *iommu,
+                                               dma_addr_t start, size_t size)
+{
+       struct list_head *pos;
+
+       list_for_each(pos, &iommu->dma_list) {
+               struct vfio_dma_map_entry *dma;
+
+               dma = list_entry(pos, struct vfio_dma_map_entry, list);
+               if (ranges_overlap(dma->iova, NPAGE_TO_SIZE(dma->npage),
+                                  start, size))
+                       return dma;
+       }
+       return NULL;
+}
+
+static long vfio_remove_dma_overlap(struct vfio_iommu *iommu, dma_addr_t start,
+                                   size_t size, struct vfio_dma_map_entry *dma)
+{
+       struct vfio_dma_map_entry *split;
+       long npage_lo, npage_hi;
+
+       /* Existing dma region is completely covered, unmap all */
+       if (start <= dma->iova &&
+           start + size >= dma->iova + NPAGE_TO_SIZE(dma->npage)) {
+               vfio_dma_unmap(iommu, dma->iova, dma->npage, dma->prot);
+               list_del(&dma->list);
+               npage_lo = dma->npage;
+               kfree(dma);
+               return npage_lo;
+       }
+
+       /* Overlap low address of existing range */
+       if (start <= dma->iova) {
+               size_t overlap;
+
+               overlap = start + size - dma->iova;
+               npage_lo = overlap >> PAGE_SHIFT;
+
+               vfio_dma_unmap(iommu, dma->iova, npage_lo, dma->prot);
+               dma->iova += overlap;
+               dma->vaddr += overlap;
+               dma->npage -= npage_lo;
+               return npage_lo;
+       }
+
+       /* Overlap high address of existing range */
+       if (start + size >= dma->iova + NPAGE_TO_SIZE(dma->npage)) {
+               size_t overlap;
+
+               overlap = dma->iova + NPAGE_TO_SIZE(dma->npage) - start;
+               npage_hi = overlap >> PAGE_SHIFT;
+
+               vfio_dma_unmap(iommu, start, npage_hi, dma->prot);
+               dma->npage -= npage_hi;
+               return npage_hi;
+       }
+
+       /* Split existing */
+       npage_lo = (start - dma->iova) >> PAGE_SHIFT;
+       npage_hi = dma->npage - (size >> PAGE_SHIFT) - npage_lo;
+
+       split = kzalloc(sizeof *split, GFP_KERNEL);
+       if (!split)
+               return -ENOMEM;
+
+       vfio_dma_unmap(iommu, start, size >> PAGE_SHIFT, dma->prot);
+
+       dma->npage = npage_lo;
+
+       split->npage = npage_hi;
+       split->iova = start + size;
+       split->vaddr = dma->vaddr + NPAGE_TO_SIZE(npage_lo) + size;
+       split->prot = dma->prot;
+       list_add(&split->list, &iommu->dma_list);
+       return size >> PAGE_SHIFT;
+}
+
+static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
+                            struct vfio_dma_unmap *unmap)
+{
+       long ret = 0, npage = unmap->size >> PAGE_SHIFT;
+       struct list_head *pos, *tmp;
+       uint64_t mask;
+
+       mask = ((uint64_t)1 << __ffs(iommu->domain->ops->pgsize_bitmap)) - 1;
+
+       if (unmap->iova & mask)
+               return -EINVAL;
+       if (unmap->size & mask)
+               return -EINVAL;
+
+       /* XXX We still break these down into PAGE_SIZE */
+       WARN_ON(mask & PAGE_MASK);
+
+       mutex_lock(&iommu->lock);
+
+       list_for_each_safe(pos, tmp, &iommu->dma_list) {
+               struct vfio_dma_map_entry *dma;
+
+               dma = list_entry(pos, struct vfio_dma_map_entry, list);
+               if (ranges_overlap(dma->iova, NPAGE_TO_SIZE(dma->npage),
+                                  unmap->iova, unmap->size)) {
+                       ret = vfio_remove_dma_overlap(iommu, unmap->iova,
+                                                     unmap->size, dma);
+                       if (ret > 0)
+                               npage -= ret;
+                       if (ret < 0 || npage == 0)
+                               break;
+               }
+       }
+       mutex_unlock(&iommu->lock);
+       return ret > 0 ? 0 : (int)ret;
+}
+
+static int vfio_dma_do_map(struct vfio_iommu *iommu, struct vfio_dma_map *map)
+{
+       struct vfio_dma_map_entry *dma, *pdma = NULL;
+       dma_addr_t iova = map->iova;
+       unsigned long locked, lock_limit, vaddr = map->vaddr;
+       size_t size = map->size;
+       int ret = 0, prot = 0;
+       uint64_t mask;
+       long npage;
+
+       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 (vaddr & mask)
+               return -EINVAL;
+       if (iova & mask)
+               return -EINVAL;
+       if (size & mask)
+               return -EINVAL;
+
+       /* XXX We still break these down into PAGE_SIZE */
+       WARN_ON(mask & PAGE_MASK);
+
+       /* Don't allow IOVA wrap */
+       if (iova + size && iova + size < iova)
+               return -EINVAL;
+
+       /* Don't allow virtual address wrap */
+       if (vaddr + size && vaddr + size < vaddr)
+               return -EINVAL;
+
+       npage = size >> PAGE_SHIFT;
+       if (!npage)
+               return -EINVAL;
+
+       mutex_lock(&iommu->lock);
+
+       if (vfio_find_dma(iommu, iova, size)) {
+               ret = -EBUSY;
+               goto out_lock;
+       }
+
+       /* account for locked pages */
+       locked = current->mm->locked_vm + npage;
+       lock_limit = rlimit(RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+       if (locked > lock_limit && !capable(CAP_IPC_LOCK)) {
+               printk(KERN_WARNING "%s: RLIMIT_MEMLOCK (%ld) exceeded\n",
+                       __func__, rlimit(RLIMIT_MEMLOCK));
+               ret = -ENOMEM;
+               goto out_lock;
+       }
+
+       ret = __vfio_dma_map(iommu, iova, vaddr, npage, prot);
+       if (ret)
+               goto out_lock;
+
+       /* Check if we abut a region below - nothing below 0 */
+       if (iova) {
+               dma = vfio_find_dma(iommu, iova - 1, 1);
+               if (dma && dma->prot == prot &&
+                   dma->vaddr + NPAGE_TO_SIZE(dma->npage) == vaddr) {
+
+                       dma->npage += npage;
+                       iova = dma->iova;
+                       vaddr = dma->vaddr;
+                       npage = dma->npage;
+                       size = NPAGE_TO_SIZE(npage);
+
+                       pdma = dma;
+               }
+       }
+
+       /* Check if we abut a region above - nothing above ~0 + 1 */
+       if (iova + size) {
+               dma = vfio_find_dma(iommu, iova + size, 1);
+               if (dma && dma->prot == prot &&
+                   dma->vaddr == vaddr + size) {
+
+                       dma->npage += npage;
+                       dma->iova = iova;
+                       dma->vaddr = vaddr;
+
+                       /*
+                        * If merged above and below, remove previously
+                        * merged entry.  New entry covers it.
+                        */
+                       if (pdma) {
+                               list_del(&pdma->list);
+                               kfree(pdma);
+                       }
+                       pdma = dma;
+               }
+       }
+
+       /* Isolated, new region */
+       if (!pdma) {
+               dma = kzalloc(sizeof *dma, GFP_KERNEL);
+               if (!dma) {
+                       ret = -ENOMEM;
+                       vfio_dma_unmap(iommu, iova, npage, prot);
+                       goto out_lock;
+               }
+
+               dma->npage = npage;
+               dma->iova = iova;
+               dma->vaddr = vaddr;
+               dma->prot = prot;
+               list_add(&dma->list, &iommu->dma_list);
+       }
+
+out_lock:
+       mutex_unlock(&iommu->lock);
+       return ret;
+}
+
+static int vfio_iommu_release(struct inode *inode, struct file *filep)
+{
+       struct vfio_iommu *iommu = filep->private_data;
+
+       vfio_release_iommu(iommu);
+       return 0;
+}
+
+static long vfio_iommu_unl_ioctl(struct file *filep,
+                                unsigned int cmd, unsigned long arg)
+{
+       struct vfio_iommu *iommu = filep->private_data;
+       unsigned long minsz;
+
+       if (cmd == VFIO_IOMMU_GET_INFO) {
+               struct vfio_iommu_info info;
+
+               minsz = offsetofend(struct vfio_iommu_info, iova_pgsizes);
+
+               if (copy_from_user(&info, (void __user *)arg, minsz))
+                       return -EFAULT;
+
+               if (info.argsz < minsz)
+                       return -EINVAL;
+
+               info.flags = 0;
+
+               /*
+                * XXX Need to define an interface in IOMMU API for this.
+                * Currently only compatible with x86 VT-d/AMD-Vi which
+                * do page table based mapping and have no constraints here.
+                */
+               info.iova_start = 0;
+               info.iova_size = ~info.iova_start;
+               info.iova_entries = ~info.iova_start;
+               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_dma_map map;
+               uint32_t mask = VFIO_DMA_MAP_FLAG_READ |
+                               VFIO_DMA_MAP_FLAG_WRITE;
+
+               minsz = offsetofend(struct vfio_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_dma_unmap unmap;
+
+               minsz = offsetofend(struct vfio_dma_unmap, size);
+
+               if (copy_from_user(&unmap, (void __user *)arg, minsz))
+                       return -EFAULT;
+
+               if (unmap.argsz < minsz || unmap.flags)
+                       return -EINVAL;
+
+               return vfio_dma_do_unmap(iommu, &unmap);
+       }
+
+       return -ENOTTY;
+}
+
+#ifdef CONFIG_COMPAT
+static long vfio_iommu_compat_ioctl(struct file *filep,
+                                   unsigned int cmd, unsigned long arg)
+{
+       arg = (unsigned long)compat_ptr(arg);
+       return vfio_iommu_unl_ioctl(filep, cmd, arg);
+}
+#endif /* CONFIG_COMPAT */
+
+const struct file_operations vfio_iommu_fops = {
+       .owner          = THIS_MODULE,
+       .release        = vfio_iommu_release,
+       .unlocked_ioctl = vfio_iommu_unl_ioctl,
+#ifdef CONFIG_COMPAT
+       .compat_ioctl   = vfio_iommu_compat_ioctl,
+#endif
+};