powerpc/pseries: Send payload with ibm,send-hvpipe-msg RTAS

JIRA: https://issues.redhat.com/browse/RHEL-101849

Conflicts:
	- Use rtas_token() instead of rtas_function_token()
	- Use 0 for RTAS_SUCCESS (This definition needs upstream 9592aa5
	  "powerpc/rtas: Add function return status constants")

commit 56dbc66
Author: Haren Myneni <haren@linux.ibm.com>
Date:   Tue Sep 9 01:43:56 2025 -0700

    powerpc/pseries: Send payload with ibm,send-hvpipe-msg RTAS

    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
    4048 bytes. writev() can be used in future when supported more
    than one buffer.

    Signed-off-by: Haren Myneni <haren@linux.ibm.com>
    Tested-by: Shashank MS <shashank.gowda@in.ibm.com>
    Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>
    Reviewed-by: Tyrel Datwyler <tyreld@linux.ibm.com>
    Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
    Link: https://patch.msgid.link/20250909084402.1488456-5-haren@linux.ibm.com

Signed-off-by: Mamatha Inamdar <minamdar@redhat.com>

Author: Mamatha Inamdar

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_token("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 0:		/* Success */
+		ret = 0;
+		break;
+	case RTAS_HARDWARE_ERROR:
+		ret = -EIO;
+		break;
+	case RTAS_INVALID_PARAMETER:
+		ret = -EINVAL;
+		break;
+	case RTAS_HVPIPE_CLOSED:
+		ret = -EPIPE;
+		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 +124,81 @@ 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;
+	__be64 *area_be;
 
 	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_be = (__be64 *)rtas_work_area_raw_buf(work_area);
+	/* header */
+	area_be[0] = cpu_to_be64(len);
+
+	work_buf = rtas_work_area_alloc(SZ_4K);
+	if (!work_buf) {
+		ret = -ENOMEM;
+		goto out_work;
+	}
+	/* First buffer address */
+	area_be[1] = cpu_to_be64(rtas_work_area_phys(work_buf));
+	/* First buffer address length */
+	area_be[2] = 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;
 }
 
 /*

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 */