dmaengine: idxd: create kmem cache for event log fault items

Add a kmem cache per device for allocating event log fault context. The
context allows an event log entry to be copied and passed to a software
workqueue to be processed. Due to each device can have different sized
event log entry depending on device type, it's not possible to have a
global kmem cache.

Tested-by: Tony Zhu <tony.zhu@intel.com>
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Co-developed-by: Fenghua Yu <fenghua.yu@intel.com>
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: https://lore.kernel.org/r/20230407203143.2189681-8-fenghua.yu@intel.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>

drivers/dma/idxd/idxd.h

@@ -274,6 +274,15 @@ struct idxd_evl {
 	u16 head;
 };
 
+struct idxd_evl_fault {
+	struct work_struct work;
+	struct idxd_wq *wq;
+	u8 status;
+
+	/* make this last member always */
+	struct __evl_entry entry[];
+};
+
 struct idxd_device {
 	struct idxd_dev idxd_dev;
 	struct idxd_driver_data *data;
@@ -331,6 +340,7 @@ struct idxd_device {
 
 	unsigned long *opcap_bmap;
 	struct idxd_evl *evl;
+	struct kmem_cache *evl_cache;
 
 	struct dentry *dbgfs_dir;
 	struct dentry *dbgfs_evl_file;

drivers/dma/idxd/init.c

@@ -345,6 +345,15 @@ static int idxd_init_evl(struct idxd_device *idxd)
 
 	spin_lock_init(&evl->lock);
 	evl->size = IDXD_EVL_SIZE_MIN;
+
+	idxd->evl_cache = kmem_cache_create(dev_name(idxd_confdev(idxd)),
+					    sizeof(struct idxd_evl_fault) + evl_ent_size(idxd),
+					    0, 0, NULL);
+	if (!idxd->evl_cache) {
+		kfree(evl);
+		return -ENOMEM;
+	}
+
 	idxd->evl = evl;
 	return 0;
 }

drivers/dma/idxd/sysfs.c

@@ -1718,6 +1718,7 @@ static void idxd_conf_device_release(struct device *dev)
 	kfree(idxd->wqs);
 	kfree(idxd->engines);
 	kfree(idxd->evl);
+	kmem_cache_destroy(idxd->evl_cache);
 	ida_free(&idxd_ida, idxd->id);
 	bitmap_free(idxd->opcap_bmap);
 	kfree(idxd);