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From 1fc9b693c54c93736c6f902f3df8b94440e8cc5d Mon Sep 17 00:00:00 2001
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From: Greg Kurz <gkurz@redhat.com>
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Date: Tue, 19 Jan 2021 15:09:53 -0500
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Subject: [PATCH 5/9] spapr: Allow memory unplug to always succeed
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RH-Author: Greg Kurz <gkurz@redhat.com>
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Message-id: <20210119150954.1017058-6-gkurz@redhat.com>
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Patchwork-id: 100686
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O-Subject: [RHEL-8.4.0 qemu-kvm PATCH v2 5/6] spapr: Allow memory unplug to always succeed
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Bugzilla: 1901837
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: Laurent Vivier <lvivier@redhat.com>
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RH-Acked-by: David Gibson <dgibson@redhat.com>
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From: Greg Kurz <groug@kaod.org>
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It is currently impossible to hot-unplug a memory device between
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machine reset and CAS.
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(qemu) device_del dimm1
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Error: Memory hot unplug not supported for this guest
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This limitation was introduced in order to provide an explicit
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error path for older guests that didn't support hot-plug event
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sources (and thus memory hot-unplug).
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The linux kernel has been supporting these since 4.11. All recent
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enough guests are thus capable of handling the removal of a memory
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device at all time, including during early boot.
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Lift the limitation for the latest machine type. This means that
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trying to unplug memory from a guest that doesn't support it will
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likely just do nothing and the memory will only get removed at
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next reboot. Such older guests can still get the existing behavior
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by using an older machine type.
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Signed-off-by: Greg Kurz <groug@kaod.org>
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Message-Id: <160794035064.23292.17560963281911312439.stgit@bahia.lan>
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Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
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(cherry picked from commit 1e8b5b1aa16b7d73ba8ba52c95d0b52329d5c9d0)
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Signed-off-by: Greg Kurz <gkurz@redhat.com>
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Conflicts:
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	hw/ppc/spapr.c
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	include/hw/ppc/spapr.h
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Conflicts around the addition of pre_6_0_memory_unplug. Ignore the
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change that sets pre_6_0_memory_unplug for older machine types.
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This is ok because pre_6_0_memory_unplug is removed in a subsequent
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patch anyway.
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Signed-off-by: Jon Maloy <jmaloy.redhat.com>
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---
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 hw/ppc/spapr.c         | 3 ++-
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 hw/ppc/spapr_events.c  | 3 ++-
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 include/hw/ppc/spapr.h | 1 +
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 3 files changed, 5 insertions(+), 2 deletions(-)
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diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
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index 992bd08aaa..f8de33e3e5 100644
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--- a/hw/ppc/spapr.c
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+++ b/hw/ppc/spapr.c
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@@ -4001,7 +4001,8 @@ static void spapr_machine_device_unplug_request(HotplugHandler *hotplug_dev,
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     SpaprMachineClass *smc = SPAPR_MACHINE_CLASS(mc);
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     if (object_dynamic_cast(OBJECT(dev), TYPE_PC_DIMM)) {
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-        if (spapr_ovec_test(sms->ov5_cas, OV5_HP_EVT)) {
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+        if (!smc->pre_6_0_memory_unplug ||
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+            spapr_ovec_test(sms->ov5_cas, OV5_HP_EVT)) {
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             spapr_memory_unplug_request(hotplug_dev, dev, errp);
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         } else {
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             /* NOTE: this means there is a window after guest reset, prior to
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diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
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index 15b92b63ad..6e284aa4bc 100644
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--- a/hw/ppc/spapr_events.c
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+++ b/hw/ppc/spapr_events.c
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@@ -547,7 +547,8 @@ static void spapr_hotplug_req_event(uint8_t hp_id, uint8_t hp_action,
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         /* we should not be using count_indexed value unless the guest
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          * supports dedicated hotplug event source
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          */
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-        g_assert(spapr_ovec_test(spapr->ov5_cas, OV5_HP_EVT));
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+        g_assert(!SPAPR_MACHINE_GET_CLASS(spapr)->pre_6_0_memory_unplug ||
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+                 spapr_ovec_test(spapr->ov5_cas, OV5_HP_EVT));
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         hp->drc_id.count_indexed.count =
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             cpu_to_be32(drc_id->count_indexed.count);
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         hp->drc_id.count_indexed.index =
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diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
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index e5e2a99046..ac6961ed16 100644
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--- a/include/hw/ppc/spapr.h
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+++ b/include/hw/ppc/spapr.h
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@@ -124,6 +124,7 @@ struct SpaprMachineClass {
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     bool pre_4_1_migration; /* don't migrate hpt-max-page-size */
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     bool linux_pci_probe;
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     bool smp_threads_vsmt; /* set VSMT to smp_threads by default */
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+    bool pre_6_0_memory_unplug;
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     bool has_power9_support;
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     void (*phb_placement)(SpaprMachineState *spapr, uint32_t index,
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-- 
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2.18.2
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