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Subject[PATCH v3 01/21] vfio: introduce vfio_iova_rw to read/write a range of IOVAs
Date
From: Yan Zhao <yan.y.zhao@intel.com>

vfio_iova_rw will read/write a range of userspace memory (starting form
device iova to iova + len -1) into a kenrel buffer without pinning the
userspace memory.

TODO: vfio needs to mark the iova dirty if vfio_iova_rw(write) is
called.

Cc: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
---
drivers/vfio/vfio.c | 45 ++++++++++++++++++
drivers/vfio/vfio_iommu_type1.c | 81 +++++++++++++++++++++++++++++++++
include/linux/vfio.h | 5 ++
3 files changed, 131 insertions(+)

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index c8482624ca34..36e91e647ed5 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1961,6 +1961,51 @@ int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn, int npage)
}
EXPORT_SYMBOL(vfio_unpin_pages);

+/*
+ * Read/Write a range of userspace IOVAs for a device into/from a kernel
+ * buffer without pinning the userspace memory
+ * @dev [in] : device
+ * @iova [in] : base IOVA of a userspace buffer
+ * @data [in] : pointer to kernel buffer
+ * @len [in] : kernel buffer length
+ * @write : indicate read or write
+ * Return error on failure or 0 on success.
+ */
+int vfio_iova_rw(struct device *dev, unsigned long iova, void *data,
+ unsigned long len, bool write)
+{
+ struct vfio_container *container;
+ struct vfio_group *group;
+ struct vfio_iommu_driver *driver;
+ int ret = 0;
+
+ if (!dev || !data || len <= 0)
+ return -EINVAL;
+
+ group = vfio_group_get_from_dev(dev);
+ if (!group)
+ return -ENODEV;
+
+ ret = vfio_group_add_container_user(group);
+ if (ret)
+ goto out;
+
+ container = group->container;
+ driver = container->iommu_driver;
+
+ if (likely(driver && driver->ops->iova_rw))
+ ret = driver->ops->iova_rw(container->iommu_data,
+ iova, data, len, write);
+ else
+ ret = -ENOTTY;
+
+ vfio_group_try_dissolve_container(group);
+out:
+ vfio_group_put(group);
+ return ret;
+}
+EXPORT_SYMBOL(vfio_iova_rw);
+
static int vfio_register_iommu_notifier(struct vfio_group *group,
unsigned long *events,
struct notifier_block *nb)
diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 2ada8e6cdb88..aee191077235 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -27,6 +27,7 @@
#include <linux/iommu.h>
#include <linux/module.h>
#include <linux/mm.h>
+#include <linux/mmu_context.h>
#include <linux/rbtree.h>
#include <linux/sched/signal.h>
#include <linux/sched/mm.h>
@@ -2326,6 +2327,85 @@ static int vfio_iommu_type1_unregister_notifier(void *iommu_data,
return blocking_notifier_chain_unregister(&iommu->notifier, nb);
}

+static int next_segment(unsigned long len, int offset)
+{
+ if (len > PAGE_SIZE - offset)
+ return PAGE_SIZE - offset;
+ else
+ return len;
+}
+
+static int vfio_iommu_type1_rw_iova_seg(struct vfio_iommu *iommu,
+ unsigned long iova, void *data,
+ unsigned long seg_len,
+ unsigned long offset,
+ bool write)
+{
+ struct mm_struct *mm;
+ unsigned long vaddr;
+ struct vfio_dma *dma;
+ bool kthread = current->mm == NULL;
+ int ret = 0;
+
+ dma = vfio_find_dma(iommu, iova, PAGE_SIZE);
+ if (!dma)
+ return -EINVAL;
+
+ mm = get_task_mm(dma->task);
+
+ if (!mm)
+ return -ENODEV;
+
+ if (kthread)
+ use_mm(mm);
+ else if (current->mm != mm) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ vaddr = dma->vaddr + iova - dma->iova + offset;
+
+ ret = write ? __copy_to_user((void __user *)vaddr,
+ data, seg_len) :
+ __copy_from_user(data, (void __user *)vaddr,
+ seg_len);
+ if (ret)
+ ret = -EFAULT;
+
+ if (kthread)
+ unuse_mm(mm);
+out:
+ mmput(mm);
+ return ret;
+}
+
+static int vfio_iommu_type1_iova_rw(void *iommu_data, unsigned long iova,
+ void *data, unsigned long len, bool write)
+{
+ struct vfio_iommu *iommu = iommu_data;
+ int offset = iova & ~PAGE_MASK;
+ int seg_len;
+ int ret = 0;
+
+ iova = iova & PAGE_MASK;
+
+ mutex_lock(&iommu->lock);
+ while ((seg_len = next_segment(len, offset)) > 0) {
+ ret = vfio_iommu_type1_rw_iova_seg(iommu, iova, data,
+ seg_len, offset, write);
+ if (ret)
+ break;
+
+ offset = 0;
+ len -= seg_len;
+ data += seg_len;
+ iova += PAGE_SIZE;
+ }
+
+ mutex_unlock(&iommu->lock);
+ return ret;
+}
+
static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
.name = "vfio-iommu-type1",
.owner = THIS_MODULE,
@@ -2338,6 +2418,7 @@ static const struct vfio_iommu_driver_ops vfio_iommu_driver_ops_type1 = {
.unpin_pages = vfio_iommu_type1_unpin_pages,
.register_notifier = vfio_iommu_type1_register_notifier,
.unregister_notifier = vfio_iommu_type1_unregister_notifier,
+ .iova_rw = vfio_iommu_type1_iova_rw,
};

static int __init vfio_iommu_type1_init(void)
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index e42a711a2800..7bf18a31bbcf 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -82,6 +82,8 @@ struct vfio_iommu_driver_ops {
struct notifier_block *nb);
int (*unregister_notifier)(void *iommu_data,
struct notifier_block *nb);
+ int (*iova_rw)(void *iommu_data, unsigned long iova,
+ void *data, unsigned long len, bool write);
};

extern int vfio_register_iommu_driver(const struct vfio_iommu_driver_ops *ops);
@@ -107,6 +109,9 @@ extern int vfio_pin_pages(struct device *dev, unsigned long *user_pfn,
extern int vfio_unpin_pages(struct device *dev, unsigned long *user_pfn,
int npage);

+extern int vfio_iova_rw(struct device *dev, unsigned long iova, void *data,
+ unsigned long len, bool write);
+
/* each type has independent events */
enum vfio_notify_type {
VFIO_IOMMU_NOTIFY = 0,
--
2.24.1
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