[PATCH RFC 4/9] powerpc/pseries: Send payload with ibm,send-hvpipe-msg RTAS

[Haren Myneni <haren@linux.ibm.com>]

ibm,send-hvpipe-msg RTAS call is used to send data to the source
(Ex: Hardware Management Console) over the hypervisor pipe. The
maximum data length of 4048 bytes is supported with this RTAS call
right now. The user space uses write() to send this payload which
invokes this RTAS. Then the write returns the buffer length
(including papr_hvpipe_hdr length) to the user space for success
or RTAS failure error.

ibm,send-hvpipe-msg call takes source ID as target and the buffer
in the form of buffer list. The buffer list format consists of
work area of size 4K to hold buffer list and number of 4K work
areas depends on buffers is as follows:

Length of Buffer List in bytes
Address of 4K buffer 1
Length of 4K buffer 1 used
...
Address of 4K buffer n
Length of 4K buffer n used

Only one buffer is used right now because of max payload size is
4088 bytes. writev() can be used in future when supported more
than one buffer.

Signed-off-by: Haren Myneni <haren@linux.ibm.com>
---
 arch/powerpc/platforms/pseries/papr-hvpipe.c | 120 ++++++++++++++++++-
 arch/powerpc/platforms/pseries/papr-hvpipe.h |   7 ++
 2 files changed, 126 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.c b/arch/powerpc/platforms/pseries/papr-hvpipe.c
index 5768d072859d..c30f4d75e645 100644
--- a/arch/powerpc/platforms/pseries/papr-hvpipe.c
+++ b/arch/powerpc/platforms/pseries/papr-hvpipe.c
@@ -14,6 +14,7 @@
 #include <linux/of.h>
 #include <asm/machdep.h>
 #include <asm/rtas.h>
+#include <asm/rtas-work-area.h>
 #include <uapi/asm/papr-hvpipe.h>
 #include "pseries.h"
 #include "papr-hvpipe.h"
@@ -59,6 +60,51 @@ static LIST_HEAD(hvpipe_src_list);
  *   return code for failure.
  */
 
+/*
+ * ibm,send-hvpipe-msg RTAS call
+ * @area: Caller-provided work area buffer to send.
+ * @srcID: Target source for the send pipe message.
+ */
+static int rtas_ibm_send_hvpipe_msg(struct rtas_work_area *area, u32 srcID)
+{
+	const s32 token = rtas_function_token(RTAS_FN_IBM_SEND_HVPIPE_MSG);
+	s32 fwrc;
+	int ret;
+
+	if (token == RTAS_UNKNOWN_SERVICE)
+		return -ENOENT;
+
+	do {
+		fwrc = rtas_call(token, 2, 1, NULL, srcID,
+				rtas_work_area_phys(area));
+
+	} while (rtas_busy_delay(fwrc));
+
+	switch (fwrc) {
+	case RTAS_SUCCESS:
+		ret = 0;
+		break;
+	case RTAS_HARDWARE_ERROR:
+		ret = -EIO;
+		break;
+	case RTAS_INVALID_PARAMETER:
+		ret = -EINVAL;
+		break;
+	case RTAS_HVPIPE_CLOSED:
+		ret = -EACCES;
+		break;
+	case RTAS_FUNC_NOT_SUPPORTED:
+		ret = -EOPNOTSUPP;
+		break;
+	default:
+		ret = -EIO;
+		pr_err_ratelimited("unexpected ibm,receive-hvpipe-msg status %d\n", fwrc);
+		break;
+	}
+
+	return ret;
+}
+
 static struct hvpipe_source_info *hvpipe_find_source(u32 srcID)
 {
 	struct hvpipe_source_info *src_info;
@@ -78,11 +124,83 @@ static ssize_t papr_hvpipe_handle_write(struct file *file,
 	const char __user *buf, size_t size, loff_t *off)
 {
 	struct hvpipe_source_info *src_info = file->private_data;
+	struct rtas_work_area *work_area, *work_buf;
+	unsigned long ret, len;
+	char *area_buf;
 
 	if (!src_info)
 		return -EIO;
 
-	return 0;
+	/*
+	 * Send HVPIPE RTAS is used to send payload to the specific
+	 * source with the input parameters source ID and the payload
+	 * as buffer list. Each entry in the buffer list contains
+	 * address/length pair of the buffer.
+	 *
+	 * The buffer list format is as follows:
+	 *
+	 * Header (length of address/length pairs and the header length)
+	 * Address of 4K buffer 1
+	 * Length of 4K buffer 1 used
+	 * ...
+	 * Address of 4K buffer n
+	 * Length of 4K buffer n used
+	 *
+	 * See PAPR 7.3.32.2 ibm,send-hvpipe-msg
+	 *
+	 * Even though can support max 1MB payload, the hypervisor
+	 * supports only 4048 bytes payload at present and also
+	 * just one address/length entry.
+	 *
+	 * writev() interface can be added in future when the
+	 * hypervisor supports multiple buffer list entries.
+	 */
+	/* HVPIPE_MAX_WRITE_BUFFER_SIZE = 4048 bytes */
+	if ((size > (HVPIPE_HDR_LEN + HVPIPE_MAX_WRITE_BUFFER_SIZE)) ||
+		(size <= HVPIPE_HDR_LEN))
+		return -EINVAL;
+
+	/*
+	 * The length of (address + length) pair + the length of header
+	 */
+	len = (2 * sizeof(u64)) + sizeof(u64);
+	size -= HVPIPE_HDR_LEN;
+	buf += HVPIPE_HDR_LEN;
+	mutex_lock(&rtas_ibm_send_hvpipe_msg_lock);
+	work_area = rtas_work_area_alloc(SZ_4K);
+	if (!work_area) {
+		ret = -ENOMEM;
+		goto out;
+	}
+	area_buf = rtas_work_area_raw_buf(work_area);
+	/* header */
+	*(u64 *)area_buf = cpu_to_be64(len);
+	area_buf += sizeof(u64);
+
+	work_buf = rtas_work_area_alloc(SZ_4K);
+	if (!area_buf) {
+		ret = -ENOMEM;
+		goto out_work;
+	}
+	/* First buffer address */
+	*(u64 *)area_buf = cpu_to_be64(rtas_work_area_phys(work_buf));
+	area_buf += sizeof(u64);
+	/* First buffer address length */
+	*(u64 *)area_buf = cpu_to_be64(size);
+
+	if (!copy_from_user(rtas_work_area_raw_buf(work_buf), buf, size)) {
+		ret = rtas_ibm_send_hvpipe_msg(work_area, src_info->srcID);
+		if (!ret)
+			ret = size + HVPIPE_HDR_LEN;
+	} else
+		ret = -EPERM;
+
+	rtas_work_area_free(work_buf);
+out_work:
+	rtas_work_area_free(work_area);
+out:
+	mutex_unlock(&rtas_ibm_send_hvpipe_msg_lock);
+	return ret;
 }
 
 /*
diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.h b/arch/powerpc/platforms/pseries/papr-hvpipe.h
index 3b6f9e737913..6f98da4ec45f 100644
--- a/arch/powerpc/platforms/pseries/papr-hvpipe.h
+++ b/arch/powerpc/platforms/pseries/papr-hvpipe.h
@@ -3,6 +3,13 @@
 #define _PAPR_HVPIPE_H
 
 #define	HVPIPE_HMC_ID_MASK	0x02000000 /*02-HMC,00-reserved and HMC ID */
+#define	HVPIPE_MAX_WRITE_BUFFER_SIZE	4048
+/*
+ * hvpipe specific RTAS return values
+ */
+#define	RTAS_HVPIPE_CLOSED		-4
+
+#define	HVPIPE_HDR_LEN	sizeof(struct papr_hvpipe_hdr)
 
 struct hvpipe_source_info {
 	struct list_head list;	/* list of sources */
-- 
2.43.5