ppc patch queue for 2021-04-21

Here's what I hope is the last ppc related pull request for qemu-6.0.
 
 The 2 patches here revert a behavioural change that after further
 discussion we concluded was a bad idea (adding a timeout for
 possibly-failed hot unplug requests).  Instead it implements a
 different approach to the original problem: we again let unplug
 requests the guest doesn't respond to remain pending indefinitely, but
 no longer allow those to block attempts to retry the same unplug
 again.
 
 The change is a bit more complex than I'd like for this late in the
 freeze.  Nonetheless, I think it's important to merge this for 6.0, so
 we don't allow a release which has the probably-a-bad-idea timeout
 behaviour.
 -----BEGIN PGP SIGNATURE-----
 
 iQIzBAABCAAdFiEEdfRlhq5hpmzETofcbDjKyiDZs5IFAmBz2eYACgkQbDjKyiDZ
 s5L1bw//XYKENrHBOgP7TCU+q2895PpCn5jxarPMrpX1fee1mlu+ncskZtlMQr8b
 C8zaWiUO9V6ezknVvqTe/4Wx+DmahGyrHwJQ/Fqj6o7C+057jEumPqBTuQFrNwz+
 4noougivOn1bVR5+vwDqAvNvO2xe49RPVd3kchHUe6tYHEa/k2kwqHeSFLZtm52R
 MusDWOD8FTxfY5uIy2LH4i2/Qe4PMn7by9ZJuldDAegHP4qn+Ffv5fO3a+HlDpOC
 KLwIub/PkLl5dtP4lru+PDgIpYwzdzZBDT/wb+OCspb4/ujqufJixt9DglnWQjEW
 3MwNK8ZnaiyrC8v9mFHzmcIJaRFQE55cr8bviB1SupJYJKB5YKuWMKKA+5E3LUuV
 VEbGzdcjP8xv0F7GzARsj8tt5iH54UJYbWLVxNy33tIfLbBrdbOH28DRhnKNZ3Y8
 f8Tz4VOKrqFL2ybQXOmSpitf5/h0nUMFRt2jZdhZLhcQ09b49k9loxPGAQoqB3aW
 HuIF3JSWnyAfFRxQjTsjzBDlgGQlghUEKj0fAqIx6SBhWJq5fg+nJ5hM1BEZIKfa
 gsy/Whs458YcSS/ArPPJ3vWC/RU8JvAAQcgSQF4AAAu/3h4FVnPCJGE8d7Jdsqdr
 KK8Y4y1PsXg7Ar7L1qTGJNzM4PKaAh4m8Mm8LLp6sVr4bAOl654=
 =fIJT
 -----END PGP SIGNATURE-----

Merge remote-tracking branch 'remotes/dg-gitlab/tags/ppc-for-6.0-20210412' into staging

ppc patch queue for 2021-04-21

Here's what I hope is the last ppc related pull request for qemu-6.0.

The 2 patches here revert a behavioural change that after further
discussion we concluded was a bad idea (adding a timeout for
possibly-failed hot unplug requests).  Instead it implements a
different approach to the original problem: we again let unplug
requests the guest doesn't respond to remain pending indefinitely, but
no longer allow those to block attempts to retry the same unplug
again.

The change is a bit more complex than I'd like for this late in the
freeze.  Nonetheless, I think it's important to merge this for 6.0, so
we don't allow a release which has the probably-a-bad-idea timeout
behaviour.

# gpg: Signature made Mon 12 Apr 2021 06:25:58 BST
# gpg:                using RSA key 75F46586AE61A66CC44E87DC6C38CACA20D9B392
# gpg: Good signature from "David Gibson <david@gibson.dropbear.id.au>" [full]
# gpg:                 aka "David Gibson (Red Hat) <dgibson@redhat.com>" [full]
# gpg:                 aka "David Gibson (ozlabs.org) <dgibson@ozlabs.org>" [full]
# gpg:                 aka "David Gibson (kernel.org) <dwg@kernel.org>" [unknown]
# Primary key fingerprint: 75F4 6586 AE61 A66C C44E  87DC 6C38 CACA 20D9 B392

* remotes/dg-gitlab/tags/ppc-for-6.0-20210412:
  spapr.c: always pulse guest IRQ in spapr_core_unplug_request()
  spapr: rollback 'unplug timeout' for CPU hotunplugs

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

hw/ppc/spapr.c

@@ -3777,12 +3777,17 @@ void spapr_core_unplug_request(HotplugHandler *hotplug_dev, DeviceState *dev,
 
     if (!spapr_drc_unplug_requested(drc)) {
         spapr_drc_unplug_request(drc);
-        spapr_hotplug_req_remove_by_index(drc);
-    } else {
-        error_setg(errp, "core-id %d unplug is still pending, %d seconds "
-                   "timeout remaining",
-                   cc->core_id, spapr_drc_unplug_timeout_remaining_sec(drc));
     }
+
+    /*
+     * spapr_hotplug_req_remove_by_index is left unguarded, out of the
+     * "!spapr_drc_unplug_requested" check, to allow for multiple IRQ
+     * pulses removing the same CPU. Otherwise, in an failed hotunplug
+     * attempt (e.g. the kernel will refuse to remove the last online
+     * CPU), we will never attempt it again because unplug_requested
+     * will still be 'true' in that case.
+     */
+    spapr_hotplug_req_remove_by_index(drc);
 }
 
 int spapr_core_dt_populate(SpaprDrc *drc, SpaprMachineState *spapr,

hw/ppc/spapr_drc.c

@@ -57,8 +57,6 @@ static void spapr_drc_release(SpaprDrc *drc)
     drck->release(drc->dev);
 
     drc->unplug_requested = false;
-    timer_del(drc->unplug_timeout_timer);
-
     g_free(drc->fdt);
     drc->fdt = NULL;
     drc->fdt_start_offset = 0;
@@ -372,17 +370,6 @@ static void prop_get_fdt(Object *obj, Visitor *v, const char *name,
     } while (fdt_depth != 0);
 }
 
-static void spapr_drc_start_unplug_timeout_timer(SpaprDrc *drc)
-{
-    SpaprDrcClass *drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
-
-    if (drck->unplug_timeout_seconds != 0) {
-        timer_mod(drc->unplug_timeout_timer,
-                  qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) +
-                  drck->unplug_timeout_seconds * 1000);
-    }
-}
-
 void spapr_drc_attach(SpaprDrc *drc, DeviceState *d)
 {
     trace_spapr_drc_attach(spapr_drc_index(drc));
@@ -409,8 +396,6 @@ void spapr_drc_unplug_request(SpaprDrc *drc)
 
     drc->unplug_requested = true;
 
-    spapr_drc_start_unplug_timeout_timer(drc);
-
     if (drc->state != drck->empty_state) {
         trace_spapr_drc_awaiting_quiesce(spapr_drc_index(drc));
         return;
@@ -419,15 +404,6 @@ void spapr_drc_unplug_request(SpaprDrc *drc)
     spapr_drc_release(drc);
 }
 
-int spapr_drc_unplug_timeout_remaining_sec(SpaprDrc *drc)
-{
-    if (drc->unplug_requested) {
-        return timer_deadline_ms(drc->unplug_timeout_timer) / 1000;
-    }
-
-    return 0;
-}
-
 bool spapr_drc_reset(SpaprDrc *drc)
 {
     SpaprDrcClass *drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);
@@ -499,23 +475,11 @@ static bool spapr_drc_needed(void *opaque)
         spapr_drc_unplug_requested(drc);
 }
 
-static int spapr_drc_post_load(void *opaque, int version_id)
-{
-    SpaprDrc *drc = opaque;
-
-    if (drc->unplug_requested) {
-        spapr_drc_start_unplug_timeout_timer(drc);
-    }
-
-    return 0;
-}
-
 static const VMStateDescription vmstate_spapr_drc = {
     .name = "spapr_drc",
     .version_id = 1,
     .minimum_version_id = 1,
     .needed = spapr_drc_needed,
-    .post_load = spapr_drc_post_load,
     .fields  = (VMStateField []) {
         VMSTATE_UINT32(state, SpaprDrc),
         VMSTATE_END_OF_LIST()
@@ -526,15 +490,6 @@ static const VMStateDescription vmstate_spapr_drc = {
     }
 };
 
-static void drc_unplug_timeout_cb(void *opaque)
-{
-    SpaprDrc *drc = opaque;
-
-    if (drc->unplug_requested) {
-        drc->unplug_requested = false;
-    }
-}
-
 static void drc_realize(DeviceState *d, Error **errp)
 {
     SpaprDrc *drc = SPAPR_DR_CONNECTOR(d);
@@ -557,11 +512,6 @@ static void drc_realize(DeviceState *d, Error **errp)
     object_property_add_alias(root_container, link_name,
                               drc->owner, child_name);
     g_free(link_name);
-
-    drc->unplug_timeout_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
-                                             drc_unplug_timeout_cb,
-                                             drc);
-
     vmstate_register(VMSTATE_IF(drc), spapr_drc_index(drc), &vmstate_spapr_drc,
                      drc);
     trace_spapr_drc_realize_complete(spapr_drc_index(drc));
@@ -579,7 +529,6 @@ static void drc_unrealize(DeviceState *d)
     name = g_strdup_printf("%x", spapr_drc_index(drc));
     object_property_del(root_container, name);
     g_free(name);
-    timer_free(drc->unplug_timeout_timer);
 }
 
 SpaprDrc *spapr_dr_connector_new(Object *owner, const char *type,
@@ -721,7 +670,6 @@ static void spapr_drc_cpu_class_init(ObjectClass *k, void *data)
     drck->drc_name_prefix = "CPU ";
     drck->release = spapr_core_release;
     drck->dt_populate = spapr_core_dt_populate;
-    drck->unplug_timeout_seconds = 15;
 }
 
 static void spapr_drc_pci_class_init(ObjectClass *k, void *data)

include/hw/ppc/spapr_drc.h

@@ -187,8 +187,6 @@ typedef struct SpaprDrc {
     bool unplug_requested;
     void *fdt;
     int fdt_start_offset;
-
-    QEMUTimer *unplug_timeout_timer;
 } SpaprDrc;
 
 struct SpaprMachineState;
@@ -211,8 +209,6 @@ typedef struct SpaprDrcClass {
 
     int (*dt_populate)(SpaprDrc *drc, struct SpaprMachineState *spapr,
                        void *fdt, int *fdt_start_offset, Error **errp);
-
-    int unplug_timeout_seconds;
 } SpaprDrcClass;
 
 typedef struct SpaprDrcPhysical {
@@ -248,7 +244,6 @@ int spapr_dt_drc(void *fdt, int offset, Object *owner, uint32_t drc_type_mask);
  */
 void spapr_drc_attach(SpaprDrc *drc, DeviceState *d);
 void spapr_drc_unplug_request(SpaprDrc *drc);
-int spapr_drc_unplug_timeout_remaining_sec(SpaprDrc *drc);
 
 /*
  * Reset all DRCs, causing pending hot-plug/unplug requests to complete.

include/qemu/timer.h

@@ -797,14 +797,6 @@ static inline int64_t get_max_clock_jump(void)
     return 60 * NANOSECONDS_PER_SECOND;
 }
 
-/**
- * timer_deadline_ms:
- *
- * Returns the remaining miliseconds for @timer to expire, or zero
- * if the timer is no longer pending.
- */
-int64_t timer_deadline_ms(QEMUTimer *timer);
-
 /*
  * Low level clock functions
  */

util/qemu-timer.c

@@ -242,19 +242,6 @@ int64_t timerlist_deadline_ns(QEMUTimerList *timer_list)
     return delta;
 }
 
-/*
- * Returns the time remaining for the deadline, in ms.
- */
-int64_t timer_deadline_ms(QEMUTimer *timer)
-{
-    if (timer_pending(timer)) {
-        return qemu_timeout_ns_to_ms(timer->expire_time) -
-               qemu_clock_get_ms(timer->timer_list->clock->type);
-    }
-
-    return 0;
-}
-
 /* Calculate the soonest deadline across all timerlists attached
  * to the clock. This is used for the icount timeout so we
  * ignore whether or not the clock should be used in deadline