[PATCH v7 16/18] iommufd: Add APIs to preserve/unpreserve a vfio cdev

[Samiullah Khawaja]

Add APIs that can be used to preserve and unpreserve a vfio cdev. Use
the APIs exported by the IOMMU core to preserve/unpreserve device.

The LUO token of the preserved iommufd is fetched and returned back to
the caller as that can be used during restore to get the restored
iommufd.

Signed-off-by: Samiullah Khawaja <skhawaja@xxxxxxxxxx>
Reviewed-by: Pranjal Shrivastava <praan@xxxxxxxxxx>
---
 drivers/iommu/iommufd/device.c          | 153 ++++++++++++++++++++++++
 drivers/iommu/iommufd/iommufd_private.h |   3 +
 include/linux/iommufd.h                 |  33 +++++
 3 files changed, 189 insertions(+)

diff --git a/drivers/iommu/iommufd/device.c b/drivers/iommu/iommufd/device.c
index 1b0bdf57ac8a..1e42e85af819 100644
--- a/drivers/iommu/iommufd/device.c
+++ b/drivers/iommu/iommufd/device.c
@@ -2,6 +2,7 @@
 /* Copyright (c) 2021-2022, NVIDIA CORPORATION & AFFILIATES
  */
 #include <linux/iommu.h>
+#include <linux/iommu-liveupdate.h>
 #include <linux/iommufd.h>
 #include <linux/pci-ats.h>
 #include <linux/slab.h>
@@ -686,6 +687,10 @@ int iommufd_hw_pagetable_attach(struct iommufd_hw_pagetable *hwpt,
 	int rc;
 
 	mutex_lock(&igroup->lock);
+	if (iommufd_device_is_preserved(idev)) {
+		rc = -EBUSY;
+		goto err_unlock;
+	}
 
 	attach = xa_cmpxchg(&igroup->pasid_attach, pasid, NULL,
 			    XA_ZERO_ENTRY, GFP_KERNEL);
@@ -869,6 +874,10 @@ iommufd_device_do_replace(struct iommufd_device *idev, ioasid_t pasid,
 	int rc;
 
 	mutex_lock(&igroup->lock);
+	if (iommufd_device_is_preserved(idev)) {
+		rc = -EBUSY;
+		goto err_unlock;
+	}
 
 	attach = xa_load(&igroup->pasid_attach, pasid);
 	if (!attach) {
@@ -1749,3 +1758,147 @@ int iommufd_get_hw_info(struct iommufd_ucmd *ucmd)
 	iommufd_put_object(ucmd->ictx, &idev->obj);
 	return rc;
 }
+
+#ifdef CONFIG_IOMMU_LIVEUPDATE
+static bool _iommufd_device_has_pasid_attachments(struct iommufd_device *idev)
+{
+	struct iommufd_group *igroup = idev->igroup;
+	unsigned long start = IOMMU_NO_PASID;
+
+	if (xa_find_after(&igroup->pasid_attach, &start, UINT_MAX, XA_PRESENT))
+		return true;
+
+	return false;
+}
+
+/**
+ * iommufd_device_preserve() - Preserve an iommufd device across live update
+ * @s: Live update session
+ * @idev: Target iommufd device
+ * @iommufd_tokenp: Pointer to store outgoing iommufd token
+ *
+ * Return: 0 on success, or negative error code.
+ */
+int iommufd_device_preserve(struct liveupdate_session *s,
+			    struct iommufd_device *idev,
+			    u64 *iommufd_tokenp)
+{
+	struct iommufd_hwpt_paging *hwpt_paging;
+	struct iommufd_hw_pagetable *hwpt;
+	struct iommufd_attach *attach;
+	struct iommufd_group *igroup;
+	int ret;
+
+	if (!idev)
+		return -EINVAL;
+
+	if (iommufd_device_is_noiommu(idev))
+		return -EOPNOTSUPP;
+
+	igroup = idev->igroup;
+	mutex_lock(&igroup->lock);
+	if (idev->liveupdate_preserved) {
+		ret = -EBUSY;
+		goto out;
+	}
+
+	if (_iommufd_device_has_pasid_attachments(idev)) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	attach = xa_load(&igroup->pasid_attach, IOMMU_NO_PASID);
+	if (!attach) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	if (!xa_load(&attach->device_array, idev->obj.id)) {
+		ret = -ENOENT;
+		goto out;
+	}
+
+	hwpt = attach->hwpt;
+	if (!hwpt_is_paging(hwpt)) {
+		ret = -EOPNOTSUPP;
+		goto out;
+	}
+
+	hwpt_paging = to_hwpt_paging(hwpt);
+	ret = liveupdate_get_token_outgoing(s, idev->ictx->file, iommufd_tokenp);
+	if (ret)
+		goto out;
+
+	if (!hwpt_paging->liveupdate_preserved) {
+		ret = -EINVAL;
+		goto out;
+	}
+
+	ret = iommu_preserve_device(hwpt_paging->common.domain,
+				    idev->dev,
+				    *iommufd_tokenp);
+
+	if (!ret)
+		idev->liveupdate_preserved = true;
+out:
+	mutex_unlock(&igroup->lock);
+	return ret;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_device_preserve, "IOMMUFD");
+
+/**
+ * iommufd_device_unpreserve() - Unpreserve an iommufd device
+ * @s: Live update session
+ * @idev: Target iommufd device
+ */
+void iommufd_device_unpreserve(struct liveupdate_session *s,
+			       struct iommufd_device *idev)
+{
+	struct iommufd_hwpt_paging *hwpt_paging;
+	struct iommufd_hw_pagetable *hwpt;
+	struct iommufd_attach *attach;
+	struct iommufd_group *igroup;
+
+	if (!idev)
+		return;
+
+	igroup = idev->igroup;
+	mutex_lock(&igroup->lock);
+	if (!idev->liveupdate_preserved)
+		goto out;
+
+	attach = xa_load(&igroup->pasid_attach, IOMMU_NO_PASID);
+	if (!attach) {
+		WARN(1, "IOMMU_NO_PASID attachment not found");
+		goto out;
+	}
+
+	hwpt = attach->hwpt;
+	if (WARN(!hwpt_is_paging(hwpt), "Attached HWPT is not a paging HWPT"))
+		goto out;
+
+	hwpt_paging = to_hwpt_paging(hwpt);
+	if (!hwpt_paging->liveupdate_preserved) {
+		WARN(1, "Attached domain is not preserved");
+		goto out;
+	}
+
+	iommu_unpreserve_device(idev->dev);
+	idev->liveupdate_preserved = false;
+out:
+	mutex_unlock(&igroup->lock);
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_device_unpreserve, "IOMMUFD");
+
+/**
+ * iommufd_device_is_preserved() - Check if an iommufd device is preserved
+ * @idev: Target iommufd device
+ *
+ * Return: true if preserved, false otherwise.
+ */
+bool iommufd_device_is_preserved(struct iommufd_device *idev)
+{
+	return idev && idev->liveupdate_preserved;
+}
+EXPORT_SYMBOL_NS_GPL(iommufd_device_is_preserved, "IOMMUFD");
+#endif
diff --git a/drivers/iommu/iommufd/iommufd_private.h b/drivers/iommu/iommufd/iommufd_private.h
index 69d902b69b82..df231d1e7d09 100644
--- a/drivers/iommu/iommufd/iommufd_private.h
+++ b/drivers/iommu/iommufd/iommufd_private.h
@@ -524,6 +524,9 @@ struct iommufd_device {
 	bool enforce_cache_coherency;
 	struct iommufd_vdevice *vdev;
 	bool destroying;
+#ifdef CONFIG_IOMMU_LIVEUPDATE
+	bool liveupdate_preserved;
+#endif
 };
 
 static inline struct iommufd_device *
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 3087f5b2def8..f673a07cbc32 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -9,6 +9,7 @@
 #include <linux/err.h>
 #include <linux/errno.h>
 #include <linux/iommu.h>
+#include <linux/liveupdate.h>
 #include <linux/refcount.h>
 #include <linux/types.h>
 #include <linux/xarray.h>
@@ -215,6 +216,15 @@ int iommufd_access_rw(struct iommufd_access *access, unsigned long iova,
 int iommufd_vfio_compat_ioas_get_id(struct iommufd_ctx *ictx, u32 *out_ioas_id);
 int iommufd_vfio_compat_ioas_create(struct iommufd_ctx *ictx);
 int iommufd_vfio_compat_set_no_iommu(struct iommufd_ctx *ictx);
+
+#ifdef CONFIG_IOMMU_LIVEUPDATE
+int iommufd_device_preserve(struct liveupdate_session *s,
+			    struct iommufd_device *idev,
+			    u64 *iommufd_tokenp);
+void iommufd_device_unpreserve(struct liveupdate_session *s,
+			       struct iommufd_device *idev);
+bool iommufd_device_is_preserved(struct iommufd_device *idev);
+#endif
 #else /* !CONFIG_IOMMUFD */
 static inline struct iommufd_ctx *iommufd_ctx_from_file(struct file *file)
 {
@@ -399,4 +409,27 @@ static inline void iommufd_viommu_destroy_mmap(struct iommufd_viommu *viommu,
 {
 	_iommufd_destroy_mmap(viommu->ictx, &viommu->obj, offset);
 }
+
+#if !IS_ENABLED(CONFIG_IOMMU_LIVEUPDATE) || !IS_ENABLED(CONFIG_IOMMUFD)
+/*
+ * vfio-pci live update works without IOMMU state preservation, so the device
+ * is still preserved, just without its IOMMU state.
+ */
+static inline int iommufd_device_preserve(struct liveupdate_session *s,
+					  struct iommufd_device *idev,
+					  u64 *iommufd_tokenp)
+{
+	return 0;
+}
+
+static inline void iommufd_device_unpreserve(struct liveupdate_session *s,
+					     struct iommufd_device *idev)
+{
+}
+
+static inline bool iommufd_device_is_preserved(struct iommufd_device *idev)
+{
+	return false;
+}
+#endif
 #endif
-- 
2.56.0.506.g506a7eabc5-goog