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

[Mahesh J Salgaonkar]

On 2025-08-24 23:53:45 Sun, Haren Myneni wrote:
> On Mon, 2025-08-25 at 11:28 +0530, Mahesh J Salgaonkar wrote:
> > 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 ?
> Yes typo error. It should be 4048 bytes as mentioned in the code.
> 
> > 
> > > 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) ?
> 
> 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 at linux.ibm.com>

Thanks,
-Mahesh.