virtio-pmem: Add virtio pmem driver

This patch adds virtio-pmem driver for KVM guest.

Guest reads the persistent memory range information from
Qemu over VIRTIO and registers it on nvdimm_bus. It also
creates a nd_region object with the persistent memory
range information so that existing 'nvdimm/pmem' driver
can reserve this into system memory map. This way
'virtio-pmem' driver uses existing functionality of pmem
driver to register persistent memory compatible for DAX
capable filesystems.

This also provides function to perform guest flush over
VIRTIO from 'pmem' driver when userspace performs flush
on DAX memory range.

Signed-off-by: Pankaj Gupta <pagupta@redhat.com>
Reviewed-by: Yuval Shaia <yuval.shaia@oracle.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Jakub Staron <jstaron@google.com>
Tested-by: Jakub Staron <jstaron@google.com>
Reviewed-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

1 files changed, 34 insertions, 0 deletions

diff --git a/include/uapi/linux/virtio_pmem.h b/include/uapi/linux/virtio_pmem.h
new file mode 100644
index 000000000000..efcd72f2d20d
--- /dev/null
+++ b/include/uapi/linux/virtio_pmem.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0 OR BSD-3-Clause */
+/*
+ * Definitions for virtio-pmem devices.
+ *
+ * Copyright (C) 2019 Red Hat, Inc.
+ *
+ * Author(s): Pankaj Gupta <pagupta@redhat.com>
+ */
+
+#ifndef _UAPI_LINUX_VIRTIO_PMEM_H
+#define _UAPI_LINUX_VIRTIO_PMEM_H
+
+#include <linux/types.h>
+#include <linux/virtio_ids.h>
+#include <linux/virtio_config.h>
+
+struct virtio_pmem_config {
+	__u64 start;
+	__u64 size;
+};
+
+#define VIRTIO_PMEM_REQ_TYPE_FLUSH      0
+
+struct virtio_pmem_resp {
+	/* Host return status corresponding to flush request */
+	__u32 ret;
+};
+
+struct virtio_pmem_req {
+	/* command type */
+	__u32 type;
+};
+
+#endif