[PATCH v2 4/9] powerpc/pseries: Send payload with ibm,send-hvpipe-msg RTAS

[Mahesh J Salgaonkar]

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

> than one buffer.
> 
> Signed-off-by: Haren Myneni <haren at 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) ?

> +		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;
> +}
> +
[...]

Thanks,
-Mahesh.