Excerpts from Haren Myneni's message of February 20, 2022 6:06 am:
>
> Since the VAS windows belong to the VAS hardware resource, the
> hypervisor expects the partition to close them on source partition
> and reopen them after the partition migrated on the destination
> machine.
>
> This handler is called before pseries_suspend() to close these
> windows and again invoked after migration. All active windows
> for both default and QoS types will be closed and mark them
> in-active and reopened after migration with this handler.
> During the migration, the user space receives paste instruction
> failure if it issues copy/paste on these in-active windows.
>
> Signed-off-by: Haren Myneni <ha...@linux.ibm.com>
> ---
> arch/powerpc/platforms/pseries/mobility.c | 5 ++
> arch/powerpc/platforms/pseries/vas.c | 86 +++++++++++++++++++++++
> arch/powerpc/platforms/pseries/vas.h | 6 ++
> 3 files changed, 97 insertions(+)
>
> diff --git a/arch/powerpc/platforms/pseries/mobility.c
> b/arch/powerpc/platforms/pseries/mobility.c
> index 85033f392c78..70004243e25e 100644
> --- a/arch/powerpc/platforms/pseries/mobility.c
> +++ b/arch/powerpc/platforms/pseries/mobility.c
> @@ -26,6 +26,7 @@
> #include <asm/machdep.h>
> #include <asm/rtas.h>
> #include "pseries.h"
> +#include "vas.h" /* vas_migration_handler() */
> #include "../../kernel/cacheinfo.h"
>
> static struct kobject *mobility_kobj;
> @@ -669,12 +670,16 @@ static int pseries_migrate_partition(u64 handle)
> if (ret)
> return ret;
>
> + vas_migration_handler(VAS_SUSPEND);
Not sure if there is much point having a "handler" like this that only
takes two operations. vas_migration_begin()/vas_migration_end() is
better isn't it?
Other question is why can't the suspend handler return error and handle
it here?
> +
> ret = pseries_suspend(handle);
> if (ret == 0)
> post_mobility_fixup();
> else
> pseries_cancel_migration(handle, ret);
>
> + vas_migration_handler(VAS_RESUME);
> +
> return ret;
> }
>
> diff --git a/arch/powerpc/platforms/pseries/vas.c
> b/arch/powerpc/platforms/pseries/vas.c
> index fbcf311da0ec..df22827969db 100644
> --- a/arch/powerpc/platforms/pseries/vas.c
> +++ b/arch/powerpc/platforms/pseries/vas.c
> @@ -869,6 +869,92 @@ static struct notifier_block pseries_vas_nb = {
> .notifier_call = pseries_vas_notifier,
> };
>
> +/*
> + * For LPM, all windows have to be closed on the source partition
> + * before migration and reopen them on the destination partition
> + * after migration. So closing windows during suspend and
> + * reopen them during resume.
> + */
> +int vas_migration_handler(int action)
> +{
> + struct vas_cop_feat_caps *caps;
> + int old_nr_creds, new_nr_creds = 0;
> + struct vas_caps *vcaps;
> + int i, rc = 0;
> +
> + /*
> + * NX-GZIP is not enabled. Nothing to do for migration.
> + */
> + if (!copypaste_feat)
> + return rc;
> +
> + mutex_lock(&vas_pseries_mutex);
> +
> + for (i = 0; i < VAS_MAX_FEAT_TYPE; i++) {
> + vcaps = &vascaps[i];
> + caps = &vcaps->caps;
> + old_nr_creds = atomic_read(&caps->nr_total_credits);
> +
> + rc = h_query_vas_capabilities(H_QUERY_VAS_CAPABILITIES,
> + vcaps->feat,
> + (u64)virt_to_phys(&hv_cop_caps));
> + if (!rc) {
> + new_nr_creds =
> be16_to_cpu(hv_cop_caps.target_lpar_creds);
> + /*
> + * Should not happen. But incase print messages, close
> + * all windows in the list during suspend and reopen
> + * windows based on new lpar_creds on the destination
> + * system.
> + */
> + if (old_nr_creds != new_nr_creds) {
> + pr_err("state(%d): lpar creds: %d HV lpar
> creds: %d\n",
> + action, old_nr_creds, new_nr_creds);
> + pr_err("Used creds: %d, Active creds: %d\n",
> + atomic_read(&caps->nr_used_credits),
> + vcaps->nr_open_windows -
> vcaps->nr_close_wins);
Error messages should have some vague use to the administrator even if
you don't expect it or they aren't expected to know much.
"VAS NX error during LPM: credit mismatch blah"
Otherwise if it's a Linux or hypervisor bug then make it a WARN_ON, at
least then by convention the administrator knows that should be reported
and it's (possibly) non-fatal.
Thanks,
Nick
> + }
> + } else {
> + pr_err("state(%d): Get VAS capabilities failed with
> %d\n",
> + action, rc);
> + /*
> + * We can not stop migration with the current lpm
> + * implementation. So continue closing all windows in
> + * the list (during suspend) and return without
> + * opening windows (during resume) if VAS capabilities
> + * HCALL failed.
> + */
> + if (action == VAS_RESUME)
> + goto out;
> + }
> +
> + switch (action) {
> + case VAS_SUSPEND:
> + rc = reconfig_close_windows(vcaps,
> vcaps->nr_open_windows,
> + true);
> + break;
> + case VAS_RESUME:
> + atomic_set(&caps->nr_total_credits, new_nr_creds);
> + rc = reconfig_open_windows(vcaps, new_nr_creds, true);
> + break;
> + default:
> + /* should not happen */
> + pr_err("Invalid migration action %d\n", action);
> + rc = -EINVAL;
> + goto out;
> + }
> +
> + /*
> + * Ignore errors during suspend and return for resume.
> + */
> + if (rc && (action == VAS_RESUME))
> + goto out;
> + }
> +
> +out:
> + mutex_unlock(&vas_pseries_mutex);
> + return rc;
> +}
> +
> static int __init pseries_vas_init(void)
> {
> struct hv_vas_all_caps *hv_caps;
> diff --git a/arch/powerpc/platforms/pseries/vas.h
> b/arch/powerpc/platforms/pseries/vas.h
> index 4ddb1001a0aa..f7568d8c6ab0 100644
> --- a/arch/powerpc/platforms/pseries/vas.h
> +++ b/arch/powerpc/platforms/pseries/vas.h
> @@ -33,6 +33,11 @@
> #define VAS_GZIP_QOS_CAPABILITIES 0x56516F73477A6970
> #define VAS_GZIP_DEFAULT_CAPABILITIES 0x56446566477A6970
>
> +enum vas_migrate_action {
> + VAS_SUSPEND,
> + VAS_RESUME,
> +};
> +
> /*
> * Co-processor feature - GZIP QoS windows or GZIP default windows
> */
> @@ -132,4 +137,5 @@ struct pseries_vas_window {
> int sysfs_add_vas_caps(struct vas_cop_feat_caps *caps);
> int vas_reconfig_capabilties(u8 type);
> int __init sysfs_pseries_vas_init(struct vas_all_caps *vas_caps);
> +int vas_migration_handler(int action);
> #endif /* _VAS_H */
> --
> 2.27.0
>
>
>
