On 2025-08-24 23:53:45 Sun, Haren Myneni wrote:

On Mon, 2025-08-25 at 11:28 +0530, Mahesh J Salgaonkar wrote:

quoted

On 2025-08-12 15:57:08 Tue, Haren Myneni wrote:

quoted

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

Do you mean 4048 ?

Yes typo error. It should be 4048 bytes as mentioned in the code.

quoted

quoted

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;

The status -4 is Pipe connection is closed/unavailabe. Instead of
permission denied does it make sense to return -EPIPE (Broken pipe) ?

Agree, The user space should close all FDs when sees this error. Will
change it to -EPIPE.

Thanks for your suggestions.

Feel free to add my Reviewed-by:

Reviewed-by: Mahesh Salgaonkar <mahesh@linux.ibm.com>

Thanks,
-Mahesh.