From 9ebed8090b88282f9b7432258df9182b9d3944ee Mon Sep 17 00:00:00 2001

From: Greg Kurz <gkurz@redhat.com>

Date: Tue, 19 Jan 2021 15:09:52 -0500

Subject: [PATCH 4/9] spapr: Fix handling of unplugged devices during CAS and

 migration

RH-Author: Greg Kurz <gkurz@redhat.com>

Message-id: <20210119150954.1017058-5-gkurz@redhat.com>

Patchwork-id: 100685

O-Subject: [RHEL-8.4.0 qemu-kvm PATCH v2 4/6] spapr: Fix handling of unplugged devices during CAS and migration

Bugzilla: 1901837

RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>

RH-Acked-by: Laurent Vivier <lvivier@redhat.com>

RH-Acked-by: David Gibson <dgibson@redhat.com>

From: Greg Kurz <groug@kaod.org>

We already detect if a device is being hot plugged before CAS to trigger

a CAS reboot and during migration to migrate the state of the associated

DRC. But hot unplugging a device is also an asynchronous operation that

requires the guest to take action. This means that if the guest is migrated

after the hot unplug event was sent but before it could release the device

with RTAS, the destination QEMU doesn't know about the pending unplug

operation and doesn't actually remove the device when the guest finally

releases it.

Similarly, if the unplug request is fired before CAS, the guest isn't

notified of the change, just like with hotplug. It ends up booting with

the device still present in the DT and configures it, just like it was

never removed. Even weirder, since the event is still queued, it will

be eventually processed when some other unrelated event is posted to

the guest.

Enhance spapr_drc_transient() to also return true if an unplug request is

pending. This fixes the issue at CAS with a CAS reboot request and

causes the DRC state to be migrated. Some extra care is still needed to

inform the destination that an unplug request is pending : migrate the

unplug_requested field of the DRC in an optional subsection. This might

break backwards migration, but this is still better than ending with

an inconsistent guest.

Signed-off-by: Greg Kurz <groug@kaod.org>

Message-Id: <158169248798.3465937.1108351365840514270.stgit@bahia.lan>

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

(cherry picked from commit ab8584349c476f9818dc6403359c85f9ab0ad5eb)

Signed-off-by: Greg Kurz <gkurz@redhat.com>

Signed-off-by: Jon Maloy <jmaloy.redhat.com>

---

 hw/ppc/spapr_drc.c | 25 +++++++++++++++++++++++--

 1 file changed, 23 insertions(+), 2 deletions(-)

diff --git a/hw/ppc/spapr_drc.c b/hw/ppc/spapr_drc.c

index 9b498d429e..897bb7aae0 100644

--- a/hw/ppc/spapr_drc.c

+++ b/hw/ppc/spapr_drc.c

@@ -455,6 +455,22 @@ void spapr_drc_reset(SpaprDrc *drc)

     }

 }

+static bool spapr_drc_unplug_requested_needed(void *opaque)

+{

+    return spapr_drc_unplug_requested(opaque);

+}

+

+static const VMStateDescription vmstate_spapr_drc_unplug_requested = {

+    .name = "spapr_drc/unplug_requested",

+    .version_id = 1,

+    .minimum_version_id = 1,

+    .needed = spapr_drc_unplug_requested_needed,

+    .fields  = (VMStateField []) {

+        VMSTATE_BOOL(unplug_requested, SpaprDrc),

+        VMSTATE_END_OF_LIST()

+    }

+};

+

 bool spapr_drc_transient(SpaprDrc *drc)

 {

     SpaprDrcClass *drck = SPAPR_DR_CONNECTOR_GET_CLASS(drc);

@@ -470,9 +486,10 @@ bool spapr_drc_transient(SpaprDrc *drc)

     /*

      * We need to reset the DRC at CAS or to migrate the DRC state if it's

      * not equal to the expected long-term state, which is the same as the

-     * coldplugged initial state.

+     * coldplugged initial state, or if an unplug request is pending.

      */

-    return (drc->state != drck->ready_state);

+    return drc->state != drck->ready_state ||

+        spapr_drc_unplug_requested(drc);

 }

 static bool spapr_drc_needed(void *opaque)

@@ -488,6 +505,10 @@ static const VMStateDescription vmstate_spapr_drc = {

     .fields  = (VMStateField []) {

         VMSTATE_UINT32(state, SpaprDrc),

         VMSTATE_END_OF_LIST()

+    },

+    .subsections = (const VMStateDescription * []) {

+        &vmstate_spapr_drc_unplug_requested,

+        NULL

     }

 };

-- 

2.18.2