Blame SOURCES/kvm-spapr-Improve-handling-of-memory-unplug-with-old-gue.patch

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From f94b3a4eb9d709f1f6a14ad9ad6ebcc1b67b6923 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 15:09:54 -0500
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Subject: [PATCH 6/9] spapr: Improve handling of memory unplug with old guests
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RH-Author: Greg Kurz <gkurz@redhat.com>
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Message-id: <20210119150954.1017058-7-gkurz@redhat.com>
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Patchwork-id: 100684
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O-Subject: [RHEL-8.4.0 qemu-kvm PATCH v2 6/6] spapr: Improve handling of memory unplug with old guests
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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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Since commit 1e8b5b1aa16b ("spapr: Allow memory unplug to always succeed")
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trying to unplug memory from a guest that doesn't support it (eg. rhel6)
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no longer generates an error like it used to. Instead, it leaves the
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memory around : only a subsequent reboot or manual use of drmgr within
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the guest can complete the hot-unplug sequence. A flag was added to
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SpaprMachineClass so that this new behavior only applies to the default
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machine type.
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We can do better. CAS processes all pending hot-unplug requests. This
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means that we don't really care about what the guest supports if
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the hot-unplug request happens before CAS.
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All guests that we care for, even old ones, set enough bits in OV5
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that lead to a non-empty bitmap in spapr->ov5_cas. Use that as a
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heuristic to decide if CAS has already occured or not.
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Always accept unplug requests that happen before CAS since CAS will
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process them. Restore the previous behavior of rejecting them after
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CAS when we know that the guest doesn't support memory hot-unplug.
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This behavior is suitable for all machine types : this allows to
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drop the pre_6_0_memory_unplug flag.
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Fixes: 1e8b5b1aa16b ("spapr: Allow memory unplug to always succeed")
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Signed-off-by: Greg Kurz <groug@kaod.org>
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Message-Id: <161012708715.801107.11418801796987916516.stgit@bahia.lan>
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Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
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Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
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(cherry picked from commit 73598c75df0585e039825e642adede21912dabc7)
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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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Contextual conflicts around the removal of pre_6_0_memory_unplug,
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which was only partially backported from upstream 1e8b5b1aa16b, and
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the addition of spapr_memory_hot_unplug_supported().
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Signed-off-by: Jon Maloy <jmaloy.redhat.com>
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---
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 hw/ppc/spapr.c              | 21 +++++++++++++--------
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 hw/ppc/spapr_events.c       |  3 +--
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 hw/ppc/spapr_ovec.c         |  7 +++++++
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 include/hw/ppc/spapr.h      |  2 +-
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 include/hw/ppc/spapr_ovec.h |  1 +
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 5 files changed, 23 insertions(+), 11 deletions(-)
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diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
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index f8de33e3e5..00b1ef075e 100644
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--- a/hw/ppc/spapr.c
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+++ b/hw/ppc/spapr.c
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@@ -3993,6 +3993,18 @@ static void spapr_machine_device_unplug(HotplugHandler *hotplug_dev,
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     }
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 }
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+bool spapr_memory_hot_unplug_supported(SpaprMachineState *spapr)
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+{
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+    return spapr_ovec_test(spapr->ov5_cas, OV5_HP_EVT) ||
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+        /*
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+         * CAS will process all pending unplug requests.
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+         *
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+         * HACK: a guest could theoretically have cleared all bits in OV5,
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+         * but none of the guests we care for do.
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+         */
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+        spapr_ovec_empty(spapr->ov5_cas);
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+}
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+
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 static void spapr_machine_device_unplug_request(HotplugHandler *hotplug_dev,
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                                                 DeviceState *dev, Error **errp)
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 {
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@@ -4001,16 +4013,9 @@ 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 (!smc->pre_6_0_memory_unplug ||
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-            spapr_ovec_test(sms->ov5_cas, OV5_HP_EVT)) {
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+        if (spapr_memory_hot_unplug_supported(sms)) {
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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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-             * CAS negotiation, where unplug requests will fail due to the
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-             * capability not being detected yet. This is a bit different than
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-             * the case with PCI unplug, where the events will be queued and
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-             * eventually handled by the guest after boot
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-             */
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             error_setg(errp, "Memory hot unplug not supported for this guest");
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         }
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     } else if (object_dynamic_cast(OBJECT(dev), TYPE_SPAPR_CPU_CORE)) {
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diff --git a/hw/ppc/spapr_events.c b/hw/ppc/spapr_events.c
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index 6e284aa4bc..08168acd65 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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@@ -547,8 +547,7 @@ 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_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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+        g_assert(spapr_memory_hot_unplug_supported(spapr));
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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/hw/ppc/spapr_ovec.c b/hw/ppc/spapr_ovec.c
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index 811fadf143..f858afc7d5 100644
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--- a/hw/ppc/spapr_ovec.c
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+++ b/hw/ppc/spapr_ovec.c
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@@ -135,6 +135,13 @@ bool spapr_ovec_test(SpaprOptionVector *ov, long bitnr)
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     return test_bit(bitnr, ov->bitmap) ? true : false;
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 }
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+bool spapr_ovec_empty(SpaprOptionVector *ov)
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+{
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+    g_assert(ov);
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+
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+    return bitmap_empty(ov->bitmap, OV_MAXBITS);
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+}
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+
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 static void guest_byte_to_bitmap(uint8_t entry, unsigned long *bitmap,
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                                  long bitmap_offset)
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 {
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diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
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index ac6961ed16..7aaf5d9996 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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@@ -124,7 +124,6 @@ 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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@@ -894,4 +893,5 @@ void spapr_check_pagesize(SpaprMachineState *spapr, hwaddr pagesize,
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 #define SPAPR_OV5_XIVE_BOTH     0x80 /* Only to advertise on the platform */
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 void spapr_set_all_lpcrs(target_ulong value, target_ulong mask);
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+bool spapr_memory_hot_unplug_supported(SpaprMachineState *spapr);
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 #endif /* HW_SPAPR_H */
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diff --git a/include/hw/ppc/spapr_ovec.h b/include/hw/ppc/spapr_ovec.h
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index 7891e9caac..98c73bf601 100644
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--- a/include/hw/ppc/spapr_ovec.h
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+++ b/include/hw/ppc/spapr_ovec.h
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@@ -73,6 +73,7 @@ void spapr_ovec_cleanup(SpaprOptionVector *ov);
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 void spapr_ovec_set(SpaprOptionVector *ov, long bitnr);
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 void spapr_ovec_clear(SpaprOptionVector *ov, long bitnr);
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 bool spapr_ovec_test(SpaprOptionVector *ov, long bitnr);
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+bool spapr_ovec_empty(SpaprOptionVector *ov);
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 SpaprOptionVector *spapr_ovec_parse_vector(target_ulong table_addr, int vector);
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 int spapr_ovec_populate_dt(void *fdt, int fdt_offset,
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                            SpaprOptionVector *ov, const char *name);
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-- 
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2.18.2
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