On Mon, 2025-08-25 at 14:10 +0530, Mahesh J Salgaonkar wrote:
> On 2025-08-12 15:57:13 Tue, Haren Myneni wrote:
> > The hypervisor assigns one pipe per partition for all sources and
> > assigns new pipe after migration. Also the partition ID that is
> > used by source as its target ID may be changed after the migration.
> > So disable hvpipe during SUSPEND event with ‘hvpipe enable’ system
> > parameter value = 0 and enable it after migration during RESUME
> > event with hvpipe enable’ system parameter value = 1.
> >
> > The user space calls such as ioctl()/ read() / write() / poll()
> > returns -ENXIO between SUSPEND and RESUME events. The user space
> > process can close FD and reestablish connection with new FD after
> > migration if needed (Example: source IDs are changed).
> >
> > Signed-off-by: Haren Myneni <ha...@linux.ibm.com>
> > ---
> > arch/powerpc/platforms/pseries/mobility.c | 3 +
> > arch/powerpc/platforms/pseries/papr-hvpipe.c | 64
> > ++++++++++++++++++++
> > arch/powerpc/platforms/pseries/papr-hvpipe.h | 6 ++
> > 3 files changed, 73 insertions(+)
> >
> > diff --git a/arch/powerpc/platforms/pseries/mobility.c
> > b/arch/powerpc/platforms/pseries/mobility.c
> > index 62bd8e2d5d4c..95fe802ccdfd 100644
> > --- a/arch/powerpc/platforms/pseries/mobility.c
> > +++ b/arch/powerpc/platforms/pseries/mobility.c
> > @@ -28,6 +28,7 @@
> > #include <asm/rtas.h>
> > #include "pseries.h"
> > #include "vas.h" /* vas_migration_handler() */
> > +#include "papr-hvpipe.h" /* hvpipe_migration_handler() */
> > #include "../../kernel/cacheinfo.h"
> >
> > static struct kobject *mobility_kobj;
> > @@ -744,6 +745,7 @@ static int pseries_migrate_partition(u64
> > handle)
> > * by closing VAS windows at the beginning of this
> > function.
> > */
> > vas_migration_handler(VAS_SUSPEND);
> > + hvpipe_migration_handler(HVPIPE_SUSPEND);
> >
> > ret = wait_for_vasi_session_suspending(handle);
> > if (ret)
> > @@ -770,6 +772,7 @@ static int pseries_migrate_partition(u64
> > handle)
> >
> > out:
> > vas_migration_handler(VAS_RESUME);
> > + hvpipe_migration_handler(HVPIPE_RESUME);
> >
> > return ret;
> > }
> > diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.c
> > b/arch/powerpc/platforms/pseries/papr-hvpipe.c
> > index bc3d1f0b4491..0edc1a29d64d 100644
> > --- a/arch/powerpc/platforms/pseries/papr-hvpipe.c
> > +++ b/arch/powerpc/platforms/pseries/papr-hvpipe.c
> > @@ -27,6 +27,7 @@ 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;
> > +static bool hvpipe_feature;
> >
> > /*
> > * New PowerPC FW provides support for partitions and various
> > @@ -233,6 +234,12 @@ static ssize_t papr_hvpipe_handle_write(struct
> > file *file,
> > unsigned long ret, len;
> > char *area_buf;
> >
> > + /*
> > + * Return -ENXIO during migration
> > + */
> > + if (!hvpipe_feature)
> > + return -ENXIO;
> > +
> > if (!src_info)
> > return -EIO;
> >
> > @@ -325,6 +332,12 @@ static ssize_t papr_hvpipe_handle_read(struct
> > file *file,
> > struct papr_hvpipe_hdr hdr;
> > long ret;
> >
> > + /*
> > + * Return -ENXIO during migration
> > + */
> > + if (!hvpipe_feature)
> > + return -ENXIO;
> > +
> > if (!src_info)
> > return -EIO;
> >
> > @@ -401,6 +414,12 @@ static unsigned int
> > papr_hvpipe_handle_poll(struct file *filp,
> > {
> > struct hvpipe_source_info *src_info = filp->private_data;
> >
> > + /*
> > + * Return -ENXIO during migration
> > + */
> > + if (!hvpipe_feature)
> > + return -ENXIO;
> > +
> > if (!src_info)
> > return -EIO;
> >
> > @@ -530,6 +549,12 @@ static long papr_hvpipe_dev_ioctl(struct file
> > *filp, unsigned int ioctl,
> > u32 srcID;
> > long ret;
> >
> > + /*
> > + * Return -ENXIO during migration
> > + */
> > + if (!hvpipe_feature)
> > + return -ENXIO;
> > +
> > if (get_user(srcID, argp))
> > return -EFAULT;
> >
> > @@ -688,6 +713,44 @@ static int __init enable_hvpipe_IRQ(void)
> > return 0;
> > }
> >
> > +void hvpipe_migration_handler(int action)
> > +{
> > + pr_info("hvpipe migration event %d\n", action);
> > +
> > + /*
> > + * HVPIPE is not used (Failed to create /dev/papr-hvpipe).
> > + * So nothing to do for migration.
> > + */
> > + if (!papr_hvpipe_work)
> > + return;
> > +
> > + switch (action) {
> > + case HVPIPE_SUSPEND:
> > + if (hvpipe_feature) {
> > + /*
> > + * Disable hvpipe_feature to the user
> > space.
> > + * It will be enabled with RESUME event.
> > + */
> > + hvpipe_feature = false;
> > + /*
> > + * set system parameter hvpipe 'disable'
> > + */
> > + set_hvpipe_sys_param(0);
> > + }
> > + break;
> > + case HVPIPE_RESUME:
> > + /*
> > + * set system parameter hvpipe 'enable'
> > + */
> > + if (!set_hvpipe_sys_param(1))
> > + hvpipe_feature = true;
> > + else
> > + pr_err("hvpipe is not enabled after
> > migration\n");
>
> So we will end up in else condtion if destination partition does not
> have hvpipe capability ?
Yes if the HVPIPE is not supported on the destination partition.
Generally we should not see this error message - HMC is adding some
checks whether FW supports this capability and limits the migration
before upgrade the FW. But added this printk (else condition) in case.
Thanks
Haren
>
> Thanks,
> -Mahesh.
>
> > +
> > + break;
> > + }
> > +}
> > +
> > static const struct file_operations papr_hvpipe_ops = {
> > .unlocked_ioctl = papr_hvpipe_dev_ioctl,
> > };
> > @@ -731,6 +794,7 @@ static int __init papr_hvpipe_init(void)
> >
> > if (!ret) {
> > pr_info("hvpipe feature is enabled\n");
> > + hvpipe_feature = true;
> > return 0;
> > } else
> > pr_err("hvpipe feature is not enabled %d\n", ret);
> > diff --git a/arch/powerpc/platforms/pseries/papr-hvpipe.h
> > b/arch/powerpc/platforms/pseries/papr-hvpipe.h
> > index aab7f77e087d..c343f4230865 100644
> > --- a/arch/powerpc/platforms/pseries/papr-hvpipe.h
> > +++ b/arch/powerpc/platforms/pseries/papr-hvpipe.h
> > @@ -11,6 +11,11 @@
> >
> > #define HVPIPE_HDR_LEN sizeof(struct papr_hvpipe_hdr)
> >
> > +enum hvpipe_migrate_action {
> > + HVPIPE_SUSPEND,
> > + HVPIPE_RESUME,
> > +};
> > +
> > struct hvpipe_source_info {
> > struct list_head list; /* list of sources */
> > u32 srcID;
> > @@ -33,4 +38,5 @@ struct hvpipe_event_buf {
> > /* with specified src ID */
> > };
> >
> > +void hvpipe_migration_handler(int action);
> > #endif /* _PAPR_HVPIPE_H */
> > --
> > 2.43.5
> >
> >
