[PATCH v7 10/12] nvdimm: virtio_pmem: isolate DMA request buffers

[Li Chen]

The virtio-pmem request object stores wait queues, flags, and list
pointers next to buffers mapped for virtqueue DMA. The response buffer is
mapped DMA_FROM_DEVICE, so non-coherent DMA invalidation must not share a
cache line with CPU-owned fields.

Keep the request buffer outside the DMA-from-device group and wrap only
the response buffer with __dma_from_device_group_begin/end.

Signed-off-by: Li Chen <me@linux.beauty>
---
Changes in v6:
- New patch.

 drivers/nvdimm/virtio_pmem.h | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/nvdimm/virtio_pmem.h b/drivers/nvdimm/virtio_pmem.h
index 3af92588bd9d1..8843a8b965874 100644
--- a/drivers/nvdimm/virtio_pmem.h
+++ b/drivers/nvdimm/virtio_pmem.h
@@ -10,6 +10,7 @@
 #ifndef _LINUX_VIRTIO_PMEM_H
 #define _LINUX_VIRTIO_PMEM_H
 
+#include <linux/dma-mapping.h>
 #include <linux/module.h>
 #include <uapi/linux/virtio_pmem.h>
 #include <linux/kref.h>
@@ -20,8 +21,6 @@
 
 struct virtio_pmem_request {
 	struct kref kref;
-	struct virtio_pmem_req req;
-	struct virtio_pmem_resp resp;
 
 	/* Wait queue to process deferred work after ack from host */
 	wait_queue_head_t host_acked;
@@ -31,6 +30,11 @@ struct virtio_pmem_request {
 	wait_queue_head_t wq_buf;
 	bool wq_buf_avail;
 	struct list_head list;
+
+	struct virtio_pmem_req req;
+	__dma_from_device_group_begin(resp);
+	struct virtio_pmem_resp resp;
+	__dma_from_device_group_end(resp);
 };
 
 struct virtio_pmem {
-- 
2.52.0