4 files changed, 135 insertions, 31 deletions

diff --git a/drivers/misc/cxl/api.c b/drivers/misc/cxl/api.c
index e2efc6489c6e..1b35e33d2434 100644
--- a/drivers/misc/cxl/api.c
+++ b/drivers/misc/cxl/api.c
@@ -9,18 +9,119 @@
 
 #include <linux/pci.h>
 #include <linux/slab.h>
-#include <linux/anon_inodes.h>
 #include <linux/file.h>
 #include <misc/cxl.h>
-#include <linux/fs.h>
 #include <asm/pnv-pci.h>
 #include <linux/msi.h>
+#include <linux/module.h>
+#include <linux/mount.h>
 
 #include "cxl.h"
 
+/*
+ * Since we want to track memory mappings to be able to force-unmap
+ * when the AFU is no longer reachable, we need an inode. For devices
+ * opened through the cxl user API, this is not a problem, but a
+ * userland process can also get a cxl fd through the cxl_get_fd()
+ * API, which is used by the cxlflash driver.
+ *
+ * Therefore we implement our own simple pseudo-filesystem and inode
+ * allocator. We don't use the anonymous inode, as we need the
+ * meta-data associated with it (address_space) and it is shared by
+ * other drivers/processes, so it could lead to cxl unmapping VMAs
+ * from random processes.
+ */
+
+#define CXL_PSEUDO_FS_MAGIC	0x1697697f
+
+static int cxl_fs_cnt;
+static struct vfsmount *cxl_vfs_mount;
+
+static const struct dentry_operations cxl_fs_dops = {
+	.d_dname	= simple_dname,
+};
+
+static struct dentry *cxl_fs_mount(struct file_system_type *fs_type, int flags,
+				const char *dev_name, void *data)
+{
+	return mount_pseudo(fs_type, "cxl:", NULL, &cxl_fs_dops,
+			CXL_PSEUDO_FS_MAGIC);
+}
+
+static struct file_system_type cxl_fs_type = {
+	.name		= "cxl",
+	.owner		= THIS_MODULE,
+	.mount		= cxl_fs_mount,
+	.kill_sb	= kill_anon_super,
+};
+
+
+void cxl_release_mapping(struct cxl_context *ctx)
+{
+	if (ctx->kernelapi && ctx->mapping)
+		simple_release_fs(&cxl_vfs_mount, &cxl_fs_cnt);
+}
+
+static struct file *cxl_getfile(const char *name,
+				const struct file_operations *fops,
+				void *priv, int flags)
+{
+	struct qstr this;
+	struct path path;
+	struct file *file;
+	struct inode *inode = NULL;
+	int rc;
+
+	/* strongly inspired by anon_inode_getfile() */
+
+	if (fops->owner && !try_module_get(fops->owner))
+		return ERR_PTR(-ENOENT);
+
+	rc = simple_pin_fs(&cxl_fs_type, &cxl_vfs_mount, &cxl_fs_cnt);
+	if (rc < 0) {
+		pr_err("Cannot mount cxl pseudo filesystem: %d\n", rc);
+		file = ERR_PTR(rc);
+		goto err_module;
+	}
+
+	inode = alloc_anon_inode(cxl_vfs_mount->mnt_sb);
+	if (IS_ERR(inode)) {
+		file = ERR_CAST(inode);
+		goto err_fs;
+	}
+
+	file = ERR_PTR(-ENOMEM);
+	this.name = name;
+	this.len = strlen(name);
+	this.hash = 0;
+	path.dentry = d_alloc_pseudo(cxl_vfs_mount->mnt_sb, &this);
+	if (!path.dentry)
+		goto err_inode;
+
+	path.mnt = mntget(cxl_vfs_mount);
+	d_instantiate(path.dentry, inode);
+
+	file = alloc_file(&path, OPEN_FMODE(flags), fops);
+	if (IS_ERR(file))
+		goto err_dput;
+	file->f_flags = flags & (O_ACCMODE | O_NONBLOCK);
+	file->private_data = priv;
+
+	return file;
+
+err_dput:
+	path_put(&path);
+err_inode:
+	iput(inode);
+err_fs:
+	simple_release_fs(&cxl_vfs_mount, &cxl_fs_cnt);
+err_module:
+	module_put(fops->owner);
+	return file;
+}
+
 struct cxl_context *cxl_dev_context_init(struct pci_dev *dev)
 {
-	struct address_space *mapping;
 	struct cxl_afu *afu;
 	struct cxl_context  *ctx;
 	int rc;
@@ -35,28 +136,13 @@ struct cxl_context *cxl_dev_context_init(struct pci_dev *dev)
 
 	ctx->kernelapi = true;
 
-	/*
-	 * Make our own address space since we won't have one from the
-	 * filesystem like the user api has, and even if we do associate a file
-	 * with this context we don't want to use the global anonymous inode's
-	 * address space as that can invalidate unrelated users:
-	 */
-	mapping = kmalloc(sizeof(struct address_space), GFP_KERNEL);
-	if (!mapping) {
-		rc = -ENOMEM;
-		goto err_ctx;
-	}
-	address_space_init_once(mapping);
-
 	/* Make it a slave context.  We can promote it later? */
-	rc = cxl_context_init(ctx, afu, false, mapping);
+	rc = cxl_context_init(ctx, afu, false);
 	if (rc)
-		goto err_mapping;
+		goto err_ctx;
 
 	return ctx;
 
-err_mapping:
-	kfree(mapping);
 err_ctx:
 	kfree(ctx);
 	return ERR_PTR(rc);
@@ -337,6 +423,11 @@ struct file *cxl_get_fd(struct cxl_context *ctx, struct file_operations *fops,
 {
 	struct file *file;
 	int rc, flags, fdtmp;
+	char *name = NULL;
+
+	/* only allow one per context */
+	if (ctx->mapping)
+		return ERR_PTR(-EEXIST);
 
 	flags = O_RDWR | O_CLOEXEC;
 
@@ -360,12 +451,13 @@ struct file *cxl_get_fd(struct cxl_context *ctx, struct file_operations *fops,
 	} else /* use default ops */
 		fops = (struct file_operations *)&afu_fops;
 
-	file = anon_inode_getfile("cxl", fops, ctx, flags);
+	name = kasprintf(GFP_KERNEL, "cxl:%d", ctx->pe);
+	file = cxl_getfile(name, fops, ctx, flags);
+	kfree(name);
 	if (IS_ERR(file))
 		goto err_fd;
 
-	file->f_mapping = ctx->mapping;
-
+	cxl_context_set_mapping(ctx, file->f_mapping);
 	*fd = fdtmp;
 	return file;
 
diff --git a/drivers/misc/cxl/context.c b/drivers/misc/cxl/context.c
index 5e506c19108a..ff5e7e8cb1d1 100644
--- a/drivers/misc/cxl/context.c
+++ b/drivers/misc/cxl/context.c
@@ -34,8 +34,7 @@ struct cxl_context *cxl_context_alloc(void)
 /*
  * Initialises a CXL context.
  */
-int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master,
-		     struct address_space *mapping)
+int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master)
 {
 	int i;
 
@@ -44,7 +43,7 @@ int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master,
 	ctx->master = master;
 	ctx->pid = ctx->glpid = NULL; /* Set in start work ioctl */
 	mutex_init(&ctx->mapping_lock);
-	ctx->mapping = mapping;
+	ctx->mapping = NULL;
 
 	/*
 	 * Allocate the segment table before we put it in the IDR so that we
@@ -114,6 +113,14 @@ int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master,
 	return 0;
 }
 
+void cxl_context_set_mapping(struct cxl_context *ctx,
+			struct address_space *mapping)
+{
+	mutex_lock(&ctx->mapping_lock);
+	ctx->mapping = mapping;
+	mutex_unlock(&ctx->mapping_lock);
+}
+
 static int cxl_mmap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 {
 	struct cxl_context *ctx = vma->vm_file->private_data;
@@ -300,8 +307,6 @@ static void reclaim_ctx(struct rcu_head *rcu)
 	if (ctx->ff_page)
 		__free_page(ctx->ff_page);
 	ctx->sstp = NULL;
-	if (ctx->kernelapi)
-		kfree(ctx->mapping);
 
 	kfree(ctx->irq_bitmap);
 
@@ -313,6 +318,8 @@ static void reclaim_ctx(struct rcu_head *rcu)
 
 void cxl_context_free(struct cxl_context *ctx)
 {
+	if (ctx->kernelapi && ctx->mapping)
+		cxl_release_mapping(ctx);
 	mutex_lock(&ctx->afu->contexts_lock);
 	idr_remove(&ctx->afu->contexts_idr, ctx->pe);
 	mutex_unlock(&ctx->afu->contexts_lock);
diff --git a/drivers/misc/cxl/cxl.h b/drivers/misc/cxl/cxl.h
index a144073593fa..b24d76723fb0 100644
--- a/drivers/misc/cxl/cxl.h
+++ b/drivers/misc/cxl/cxl.h
@@ -817,8 +817,9 @@ void cxl_dump_debug_buffer(void *addr, size_t size);
 void init_cxl_native(void);
 
 struct cxl_context *cxl_context_alloc(void);
-int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master,
-		     struct address_space *mapping);
+int cxl_context_init(struct cxl_context *ctx, struct cxl_afu *afu, bool master);
+void cxl_context_set_mapping(struct cxl_context *ctx,
+			struct address_space *mapping);
 void cxl_context_free(struct cxl_context *ctx);
 int cxl_context_iomap(struct cxl_context *ctx, struct vm_area_struct *vma);
 unsigned int cxl_map_irq(struct cxl *adapter, irq_hw_number_t hwirq,
@@ -877,6 +878,7 @@ void cxl_native_err_irq_dump_regs(struct cxl *adapter);
 void cxl_stop_trace(struct cxl *cxl);
 int cxl_pci_vphb_add(struct cxl_afu *afu);
 void cxl_pci_vphb_remove(struct cxl_afu *afu);
+void cxl_release_mapping(struct cxl_context *ctx);
 
 extern struct pci_driver cxl_pci_driver;
 extern struct platform_driver cxl_of_driver;
diff --git a/drivers/misc/cxl/file.c b/drivers/misc/cxl/file.c
index 77080cc5fa0a..859959f19f10 100644
--- a/drivers/misc/cxl/file.c
+++ b/drivers/misc/cxl/file.c
@@ -86,9 +86,12 @@ static int __afu_open(struct inode *inode, struct file *file, bool master)
 		goto err_put_afu;
 	}
 
-	if ((rc = cxl_context_init(ctx, afu, master, inode->i_mapping)))
+	rc = cxl_context_init(ctx, afu, master);
+	if (rc)
 		goto err_put_afu;
 
+	cxl_context_set_mapping(ctx, inode->i_mapping);
+
 	pr_devel("afu_open pe: %i\n", ctx->pe);
 	file->private_data = ctx;
 	cxl_ctx_get();