[PATCH v11 09/22] vfio iommu type1: Add task structure to vfio_dma

[Kirti Wankhede]

Add task structure to vfio_dma.
Add address space structure. Each vfio_dma structure points to the address
space of the task who mapped it.
List of address spaces is maintained in vfio_iommu structure.
>From DMA_MAP call if address space already exist in address space list,
vfio_dma points to it. If address space doesn't exist, allocate address
space, save pointer of mm to it and vfio_dma points to it.
Two tasks can share same address space and so we need keep address space
structure different from task in vfio_dma structure. vfio_dma keeps
pointer to its corresponding address space.
During DMA_UNMAP, same task who mapped it or other task who shares same
address space is allowed to unmap, otherwise unmap fails.
QEMU maps few iova ranges initially, then fork threads and from the child
thread calls DMA_UNMAP on previously mapped iova. Since child shares same
address space, DMA_UNMAP is successful.
This address space structure is used to track pages pinned by external
user in later changes.

Signed-off-by: Kirti Wankhede <kwankhede@xxxxxxxxxx>
Signed-off-by: Neo Jia <cjia@xxxxxxxxxx>
Change-Id: I7600f1bea6b384fd589fa72421ccf031bcfd9ac5
---
 drivers/vfio/vfio_iommu_type1.c | 182 +++++++++++++++++++++++++++++-----------
 1 file changed, 134 insertions(+), 48 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 422c8d198abb..8d64528dcc22 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -55,12 +55,20 @@ MODULE_PARM_DESC(disable_hugepages,
 
 struct vfio_iommu {
 	struct list_head	domain_list;
+	struct list_head	addr_space_list;
 	struct mutex		lock;
 	struct rb_root		dma_list;
 	bool			v2;
 	bool			nesting;
 };
 
+/* address space */
+struct vfio_addr_space {
+	struct mm_struct	*mm;
+	struct list_head	next;
+	atomic_t		ref_count;
+};
+
 struct vfio_domain {
 	struct iommu_domain	*domain;
 	struct list_head	next;
@@ -75,6 +83,9 @@ struct vfio_dma {
 	unsigned long		vaddr;		/* Process virtual addr */
 	size_t			size;		/* Map size (bytes) */
 	int			prot;		/* IOMMU_READ/WRITE */
+	struct vfio_addr_space	*addr_space;
+	struct task_struct	*task;
+	bool			mlock_cap;
 };
 
 struct vfio_group {
@@ -130,6 +141,18 @@ static void vfio_unlink_dma(struct vfio_iommu *iommu, struct vfio_dma *old)
 	rb_erase(&old->node, &iommu->dma_list);
 }
 
+static struct vfio_addr_space *vfio_find_addr_space(struct vfio_iommu *iommu,
+						    struct mm_struct *mm)
+{
+	struct vfio_addr_space *as;
+
+	list_for_each_entry(as, &iommu->addr_space_list, next) {
+		if (as->mm == mm)
+			return as;
+	}
+	return NULL;
+}
+
 struct vwork {
 	struct mm_struct	*mm;
 	long			npage;
@@ -273,24 +296,24 @@ static int vaddr_get_pfn(struct mm_struct *mm, unsigned long vaddr,
  * 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_remote(unsigned long vaddr, long npage,
-				    int prot, unsigned long *pfn_base)
+static long __vfio_pin_pages_remote(struct vfio_dma *dma, 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);
+	struct task_struct *task = dma->task;
+	unsigned long limit = task_rlimit(task, RLIMIT_MEMLOCK) >> PAGE_SHIFT;
+	bool lock_cap = dma->mlock_cap;
+	struct mm_struct *mm = dma->addr_space->mm;
 	long ret, i;
 	bool rsvd;
 
-	if (!current->mm)
-		return -ENODEV;
-
-	ret = vaddr_get_pfn(current->mm, vaddr, prot, pfn_base);
+	ret = vaddr_get_pfn(mm, vaddr, prot, pfn_base);
 	if (ret)
 		return ret;
 
 	rsvd = is_invalid_reserved_pfn(*pfn_base);
 
-	if (!rsvd && !lock_cap && current->mm->locked_vm + 1 > limit) {
+	if (!rsvd && !lock_cap && mm->locked_vm + 1 > limit) {
 		put_pfn(*pfn_base, prot);
 		pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n", __func__,
 			limit << PAGE_SHIFT);
@@ -299,7 +322,7 @@ static long __vfio_pin_pages_remote(unsigned long vaddr, long npage,
 
 	if (unlikely(disable_hugepages)) {
 		if (!rsvd)
-			vfio_lock_acct(current->mm, 1);
+			vfio_lock_acct(mm, 1);
 		return 1;
 	}
 
@@ -307,7 +330,7 @@ static long __vfio_pin_pages_remote(unsigned long vaddr, long npage,
 	for (i = 1, vaddr += PAGE_SIZE; i < npage; i++, vaddr += PAGE_SIZE) {
 		unsigned long pfn = 0;
 
-		ret = vaddr_get_pfn(current->mm, vaddr, prot, &pfn);
+		ret = vaddr_get_pfn(mm, vaddr, prot, &pfn);
 		if (ret)
 			break;
 
@@ -318,7 +341,7 @@ static long __vfio_pin_pages_remote(unsigned long vaddr, long npage,
 		}
 
 		if (!rsvd && !lock_cap &&
-		    current->mm->locked_vm + i + 1 > limit) {
+		    mm->locked_vm + i + 1 > limit) {
 			put_pfn(pfn, prot);
 			pr_warn("%s: RLIMIT_MEMLOCK (%ld) exceeded\n",
 				__func__, limit << PAGE_SHIFT);
@@ -327,13 +350,13 @@ static long __vfio_pin_pages_remote(unsigned long vaddr, long npage,
 	}
 
 	if (!rsvd)
-		vfio_lock_acct(current->mm, i);
+		vfio_lock_acct(mm, i);
 
 	return i;
 }
 
-static long __vfio_unpin_pages_remote(unsigned long pfn, long npage,
-				      int prot, bool do_accounting)
+static long __vfio_unpin_pages_remote(struct vfio_dma *dma, unsigned long pfn,
+				      long npage, int prot, bool do_accounting)
 {
 	unsigned long unlocked = 0;
 	long i;
@@ -342,7 +365,7 @@ static long __vfio_unpin_pages_remote(unsigned long pfn, long npage,
 		unlocked += put_pfn(pfn++, prot);
 
 	if (do_accounting)
-		vfio_lock_acct(current->mm, -unlocked);
+		vfio_lock_acct(dma->addr_space->mm, -unlocked);
 
 	return unlocked;
 }
@@ -396,7 +419,7 @@ static void vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma)
 		if (WARN_ON(!unmapped))
 			break;
 
-		unlocked += __vfio_unpin_pages_remote(phys >> PAGE_SHIFT,
+		unlocked += __vfio_unpin_pages_remote(dma, phys >> PAGE_SHIFT,
 						      unmapped >> PAGE_SHIFT,
 						      dma->prot, false);
 		iova += unmapped;
@@ -404,13 +427,20 @@ static void vfio_unmap_unpin(struct vfio_iommu *iommu, struct vfio_dma *dma)
 		cond_resched();
 	}
 
-	vfio_lock_acct(current->mm, -unlocked);
+	vfio_lock_acct(dma->addr_space->mm, -unlocked);
 }
 
 static void vfio_remove_dma(struct vfio_iommu *iommu, struct vfio_dma *dma)
 {
 	vfio_unmap_unpin(iommu, dma);
 	vfio_unlink_dma(iommu, dma);
+
+	if (atomic_dec_and_test(&dma->addr_space->ref_count)) {
+		mmput(dma->addr_space->mm);
+		put_task_struct(dma->task);
+		list_del(&dma->addr_space->next);
+		kfree(dma->addr_space);
+	}
 	kfree(dma);
 }
 
@@ -506,6 +536,12 @@ static int vfio_dma_do_unmap(struct vfio_iommu *iommu,
 	while ((dma = vfio_find_dma(iommu, unmap->iova, unmap->size))) {
 		if (!iommu->v2 && unmap->iova > dma->iova)
 			break;
+		/*
+		 * Task with same address space who mapped this iova range is
+		 * allowed to unmap the iova range.
+		 */
+		if (dma->task->mm != current->mm)
+			break;
 		unmapped += dma->size;
 		vfio_remove_dma(iommu, dma);
 	}
@@ -572,17 +608,58 @@ unwind:
 	return ret;
 }
 
+static int vfio_pin_map_dma(struct vfio_iommu *iommu, struct vfio_dma *dma,
+			    size_t map_size)
+{
+	dma_addr_t iova = dma->iova;
+	unsigned long vaddr = dma->vaddr;
+	size_t size = map_size;
+	long npage;
+	unsigned long pfn;
+	int ret = 0;
+
+	while (size) {
+		/* Pin a contiguous chunk of memory */
+		npage = __vfio_pin_pages_remote(dma, vaddr + dma->size,
+						size >> PAGE_SHIFT, dma->prot,
+						&pfn);
+		if (npage <= 0) {
+			WARN_ON(!npage);
+			ret = (int)npage;
+			break;
+		}
+
+		/* Map it! */
+		ret = vfio_iommu_map(iommu, iova + dma->size, pfn, npage,
+				     dma->prot);
+		if (ret) {
+			__vfio_unpin_pages_remote(dma, pfn, npage, dma->prot,
+						  true);
+			break;
+		}
+
+		size -= npage << PAGE_SHIFT;
+		dma->size += npage << PAGE_SHIFT;
+	}
+
+	if (ret)
+		vfio_remove_dma(iommu, dma);
+
+	return ret;
+}
+
 static int vfio_dma_do_map(struct vfio_iommu *iommu,
 			   struct vfio_iommu_type1_dma_map *map)
 {
 	dma_addr_t iova = map->iova;
 	unsigned long vaddr = map->vaddr;
 	size_t size = map->size;
-	long npage;
 	int ret = 0, prot = 0;
 	uint64_t mask;
 	struct vfio_dma *dma;
-	unsigned long pfn;
+	struct vfio_addr_space *addr_space;
+	struct mm_struct *mm;
+	bool free_addr_space_on_err = false;
 
 	/* Verify that none of our __u64 fields overflow */
 	if (map->size != size || map->vaddr != vaddr || map->iova != iova)
@@ -608,47 +685,56 @@ static int vfio_dma_do_map(struct vfio_iommu *iommu,
 	mutex_lock(&iommu->lock);
 
 	if (vfio_find_dma(iommu, iova, size)) {
-		mutex_unlock(&iommu->lock);
-		return -EEXIST;
+		ret = -EEXIST;
+		goto do_map_err;
+	}
+
+	mm = get_task_mm(current);
+	if (!mm) {
+		ret = -ENODEV;
+		goto do_map_err;
+	}
+
+	addr_space = vfio_find_addr_space(iommu, mm);
+	if (addr_space) {
+		atomic_inc(&addr_space->ref_count);
+		mmput(mm);
+	} else {
+		addr_space = kzalloc(sizeof(*addr_space), GFP_KERNEL);
+		if (!addr_space) {
+			ret = -ENOMEM;
+			goto do_map_err;
+		}
+		addr_space->mm = mm;
+		atomic_set(&addr_space->ref_count, 1);
+		list_add(&addr_space->next, &iommu->addr_space_list);
+		free_addr_space_on_err = true;
 	}
 
 	dma = kzalloc(sizeof(*dma), GFP_KERNEL);
 	if (!dma) {
-		mutex_unlock(&iommu->lock);
-		return -ENOMEM;
+		if (free_addr_space_on_err) {
+			mmput(mm);
+			list_del(&addr_space->next);
+			kfree(addr_space);
+		}
+		ret = -ENOMEM;
+		goto do_map_err;
 	}
 
 	dma->iova = iova;
 	dma->vaddr = vaddr;
 	dma->prot = prot;
+	dma->addr_space = addr_space;
+	get_task_struct(current);
+	dma->task = current;
+	dma->mlock_cap = capable(CAP_IPC_LOCK);
 
 	/* Insert zero-sized and grow as we map chunks of it */
 	vfio_link_dma(iommu, dma);
 
-	while (size) {
-		/* Pin a contiguous chunk of memory */
-		npage = __vfio_pin_pages_remote(vaddr + dma->size,
-						size >> PAGE_SHIFT, prot, &pfn);
-		if (npage <= 0) {
-			WARN_ON(!npage);
-			ret = (int)npage;
-			break;
-		}
-
-		/* Map it! */
-		ret = vfio_iommu_map(iommu, iova + dma->size, pfn, npage, prot);
-		if (ret) {
-			__vfio_unpin_pages_remote(pfn, npage, prot, true);
-			break;
-		}
-
-		size -= npage << PAGE_SHIFT;
-		dma->size += npage << PAGE_SHIFT;
-	}
-
-	if (ret)
-		vfio_remove_dma(iommu, dma);
-
+	ret = vfio_pin_map_dma(iommu, dma, size);
+do_map_err:
 	mutex_unlock(&iommu->lock);
 	return ret;
 }
-- 
2.7.0