[PATCH v4 7/9] powerpc/pseries: Enable HVPIPE event message interrupt
Madhavan Srinivasan
maddy at linux.ibm.com
Sat Sep 6 20:16:22 AEST 2025
On 8/30/25 11:33 AM, Haren Myneni wrote:
> The hypervisor signals the OS via a Hypervisor Pipe Event external
> interrupt when data is available to be received from the pipe.
> Then the OS should call RTAS check-exception and provide the input
> Event Mask as defined for the ‘ibm,hvpipe-msg-events’. In response,
> check-exception will return an event log containing an Pipe Events
> message. This message contains the source ID for which this
> message is intended to and the pipe status such as whether the
> payload is pending in the hypervisor or pipe to source is closed.
>
> If there is any user space process waiting in the wait_queue for
> the payload from this source ID, wake up that process which can
> issue read() to obtain payload with ibm,receive-hvpipe-msg RTAS
> or close FD if the pipe to source is closed.
>
> The hypervisor has one pipe per partition for all sources and it
> will not deliver another hvpipe event message until the partition
> reads the payload for the previous hvpipe event. So if the source
> ID is not found in the source list, issue the dummy
> ibm,receive-hvpipe-msg RTAS so that pipe will not blocked.
>
> Register hvpipe event source interrupt based on entries from
> /proc/device-tree//event-sources/ibm,hvpipe-msg-events property.
>
> Signed-off-by: Haren Myneni <haren at linux.ibm.com>
> Reviewed-by: Mahesh Salgaonkar <mahesh at linux.ibm.com>
> Reviewed-by: Tyrel Datwyler <tyreld at linux.ibm.com>
> Tested-by: Shashank MS <shashank.gowda at in.ibm.com>
> ---
> arch/powerpc/platforms/pseries/papr-hvpipe.c | 146 ++++++++++++++++++-
> arch/powerpc/platforms/pseries/papr-hvpipe.h | 14 ++
> 2 files changed, 155 insertions(+), 5 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.c b/arch/powerpc/platforms/pseries/papr-hvpipe.c
> index 1e7636c0b275..0969efb39d95 100644
> --- a/arch/powerpc/platforms/pseries/papr-hvpipe.c
> +++ b/arch/powerpc/platforms/pseries/papr-hvpipe.c
> @@ -22,6 +22,11 @@
> static DEFINE_SPINLOCK(hvpipe_src_list_lock);
> static LIST_HEAD(hvpipe_src_list);
>
> +static unsigned char hvpipe_ras_buf[RTAS_ERROR_LOG_MAX];
> +static struct workqueue_struct *papr_hvpipe_wq;
> +static struct work_struct *papr_hvpipe_work = NULL;
> +static int hvpipe_check_exception_token;
> +
checkpatch.pl is not happy, reporting these errors
ERROR: do not initialise statics to NULL
#53: FILE: arch/powerpc/platforms/pseries/papr-hvpipe.c:27:
+static struct work_struct *papr_hvpipe_work = NULL;
WARNING: else is not generally useful after a break or return
#205: FILE: arch/powerpc/platforms/pseries/papr-hvpipe.c:716:
+ return 0;
+ } else
total: 1 errors, 1 warnings, 183 lines checked
> /*
> * New PowerPC FW provides support for partitions and various
> * sources (Ex: remote hardware management console (HMC)) to
> @@ -556,6 +561,117 @@ static long papr_hvpipe_dev_ioctl(struct file *filp, unsigned int ioctl,
> return ret;
> }
>
> +/*
> + * papr_hvpipe_work_fn - called to issue recv HVPIPE RTAS for
> + * sources that are not monitored by user space so that pipe
> + * will not be blocked.
> + */
> +static void papr_hvpipe_work_fn(struct work_struct *work)
> +{
> + hvpipe_rtas_recv_msg(NULL, 0);
> +}
> +
> +/*
> + * HVPIPE event message IRQ handler.
> + * The hypervisor sends event IRQ if the partition has payload
> + * and generates another event only after payload is read with
> + * recv HVPIPE RTAS.
> + */
> +static irqreturn_t hvpipe_event_interrupt(int irq, void *dev_id)
> +{
> + struct hvpipe_event_buf *hvpipe_event;
> + struct pseries_errorlog *pseries_log;
> + struct hvpipe_source_info *src_info;
> + struct rtas_error_log *elog;
> + int rc;
> +
> + rc = rtas_call(hvpipe_check_exception_token, 6, 1, NULL,
> + RTAS_VECTOR_EXTERNAL_INTERRUPT, virq_to_hw(irq),
> + RTAS_HVPIPE_MSG_EVENTS, 1, __pa(&hvpipe_ras_buf),
> + rtas_get_error_log_max());
> +
> + if (rc != 0) {
> + pr_err_ratelimited("unexpected hvpipe-event-notification failed %d\n", rc);
> + return IRQ_HANDLED;
> + }
> +
> + elog = (struct rtas_error_log *)hvpipe_ras_buf;
> + if (unlikely(rtas_error_type(elog) != RTAS_TYPE_HVPIPE)) {
> + pr_warn_ratelimited("Unexpected event type %d\n",
> + rtas_error_type(elog));
> + return IRQ_HANDLED;
> + }
> +
> + pseries_log = get_pseries_errorlog(elog,
> + PSERIES_ELOG_SECT_ID_HVPIPE_EVENT);
> + hvpipe_event = (struct hvpipe_event_buf *)pseries_log->data;
> +
> + /*
> + * The hypervisor notifies partition when the payload is
> + * available to read with recv HVPIPE RTAS and it will not
> + * notify another event for any source until the previous
> + * payload is read. Means the pipe is blocked in the
> + * hypervisor until the payload is read.
> + *
> + * If the source is ready to accept payload and wakeup the
> + * corresponding FD. Hold lock and update hvpipe_status
> + * and this lock is needed in case the user space process
> + * is in release FD instead of poll() so that release()
> + * reads the payload to unblock pipe before closing FD.
> + *
> + * otherwise (means no other user process waiting for the
> + * payload, issue recv HVPIPE RTAS (papr_hvpipe_work_fn())
> + * to unblock pipe.
> + */
> + spin_lock(&hvpipe_src_list_lock);
> + src_info = hvpipe_find_source(be32_to_cpu(hvpipe_event->srcID));
> + if (src_info) {
> + u32 flags = 0;
> +
> + if (hvpipe_event->event_type & HVPIPE_LOST_CONNECTION)
> + flags = HVPIPE_LOST_CONNECTION;
> + else if (hvpipe_event->event_type & HVPIPE_MSG_AVAILABLE)
> + flags = HVPIPE_MSG_AVAILABLE;
> +
> + src_info->hvpipe_status |= flags;
> + wake_up(&src_info->recv_wqh);
> + spin_unlock(&hvpipe_src_list_lock);
> + } else {
> + spin_unlock(&hvpipe_src_list_lock);
> + /*
> + * user space is not waiting on this source. So
> + * execute receive pipe RTAS so that pipe will not
> + * be blocked.
> + */
> + if (hvpipe_event->event_type & HVPIPE_MSG_AVAILABLE)
> + queue_work(papr_hvpipe_wq, papr_hvpipe_work);
> + }
> +
> + return IRQ_HANDLED;
> +}
> +
> +static int __init enable_hvpipe_IRQ(void)
> +{
> + struct device_node *np;
> +
> + hvpipe_check_exception_token = rtas_function_token(RTAS_FN_CHECK_EXCEPTION);
> + if (hvpipe_check_exception_token == RTAS_UNKNOWN_SERVICE)
> + return -ENODEV;
> +
> + /* hvpipe events */
> + np = of_find_node_by_path("/event-sources/ibm,hvpipe-msg-events");
> + if (np != NULL) {
> + request_event_sources_irqs(np, hvpipe_event_interrupt,
> + "HPIPE_EVENT");
> + of_node_put(np);
> + } else {
> + pr_err("Can not enable hvpipe event IRQ\n");
> + return -ENODEV;
> + }
> +
> + return 0;
> +}
> +
> static const struct file_operations papr_hvpipe_ops = {
> .unlocked_ioctl = papr_hvpipe_dev_ioctl,
> };
> @@ -578,12 +694,32 @@ static int __init papr_hvpipe_init(void)
> !rtas_function_implemented(RTAS_FN_IBM_RECEIVE_HVPIPE_MSG))
> return -ENODEV;
>
> - ret = misc_register(&papr_hvpipe_dev);
> - if (ret) {
> - pr_err("misc-dev registration failed %d\n", ret);
> - return ret;
> + papr_hvpipe_work = kzalloc(sizeof(struct work_struct), GFP_ATOMIC);
> + if (!papr_hvpipe_work)
> + return -ENOMEM;
> +
> + INIT_WORK(papr_hvpipe_work, papr_hvpipe_work_fn);
> +
> + papr_hvpipe_wq = alloc_ordered_workqueue("papr hvpipe workqueue", 0);
> + if (!papr_hvpipe_wq) {
> + ret = -ENOMEM;
> + goto out;
> }
>
> - return 0;
> + ret = enable_hvpipe_IRQ();
> + if (!ret)
> + ret = misc_register(&papr_hvpipe_dev);
> +
> + if (!ret) {
> + pr_info("hvpipe feature is enabled\n");
> + return 0;
> + } else
> + pr_err("hvpipe feature is not enabled %d\n", ret);
> +
> + destroy_workqueue(papr_hvpipe_wq);
> +out:
> + kfree(papr_hvpipe_work);
> + papr_hvpipe_work = NULL;
> + return ret;
> }
> machine_device_initcall(pseries, papr_hvpipe_init);
> diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.h b/arch/powerpc/platforms/pseries/papr-hvpipe.h
> index 125658e6b596..aab7f77e087d 100644
> --- a/arch/powerpc/platforms/pseries/papr-hvpipe.h
> +++ b/arch/powerpc/platforms/pseries/papr-hvpipe.h
> @@ -19,4 +19,18 @@ struct hvpipe_source_info {
> struct task_struct *tsk;
> };
>
> +/*
> + * Source ID Format 0xCCRRQQQQ
> + * CC = indicating value is source type (ex: 0x02 for HMC)
> + * RR = 0x00 (reserved)
> + * QQQQ = 0x0000 – 0xFFFF indicating the source index indetifier
> + */
> +struct hvpipe_event_buf {
> + __be32 srcID; /* Source ID */
> + u8 event_type; /* 0x01 for hvpipe message available */
> + /* from specified src ID */
> + /* 0x02 for loss of pipe connection */
> + /* with specified src ID */
> +};
> +
> #endif /* _PAPR_HVPIPE_H */
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