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From 1e8f268e649136a29814db86735b3c20193bd133 Mon Sep 17 00:00:00 2001
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From: Alex Williamson <alex.williamson@redhat.com>
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Date: Mon, 3 Dec 2018 22:02:33 +0000
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Subject: [PATCH 16/16] postcopy: Synchronize usage of the balloon inhibitor
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RH-Author: Alex Williamson <alex.williamson@redhat.com>
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Message-id: <154387455350.27651.11210229318068647811.stgit@gimli.home>
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Patchwork-id: 83241
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O-Subject: [RHEL-8.0 qemu-kvm PATCH 7/7] postcopy: Synchronize usage of the balloon inhibitor
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Bugzilla: 1650272
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RH-Acked-by: Peter Xu <peterx@redhat.com>
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RH-Acked-by: Auger Eric <eric.auger@redhat.com>
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RH-Acked-by: Cornelia Huck <cohuck@redhat.com>
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RH-Acked-by: David Hildenbrand <david@redhat.com>
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Bugzilla: 1650272
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While the qemu_balloon_inhibit() interface appears rather general purpose,
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postcopy uses it in a last-caller-wins approach with no guarantee of balanced
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inhibits and de-inhibits.  Wrap postcopy's usage of the inhibitor to give it
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one vote overall, using the same last-caller-wins approach as previously
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implemented at the balloon level.
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Fixes: 01ccbec7bdf6 ("balloon: Allow multiple inhibit users")
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Reported-by: Christian Borntraeger <borntraeger@de.ibm.com>
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Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
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Reviewed-by: Cornelia Huck <cohuck@redhat.com>
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Reviewed-by: Juan Quintela <quintela@redhat.com>
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Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
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(cherry picked from commit 154304cd6e99e4222ed762976f9d9aca33c094d3)
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Signed-off-by: Danilo C. L. de Paula <ddepaula@redhat.com>
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---
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 migration/postcopy-ram.c | 18 ++++++++++++++++--
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 1 file changed, 16 insertions(+), 2 deletions(-)
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diff --git a/migration/postcopy-ram.c b/migration/postcopy-ram.c
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index 4a0b33b..b04e903 100644
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--- a/migration/postcopy-ram.c
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+++ b/migration/postcopy-ram.c
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@@ -400,6 +400,20 @@ int postcopy_ram_incoming_init(MigrationIncomingState *mis, size_t ram_pages)
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 }
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 /*
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+ * Manage a single vote to the QEMU balloon inhibitor for all postcopy usage,
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+ * last caller wins.
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+ */
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+static void postcopy_balloon_inhibit(bool state)
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+{
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+    static bool cur_state = false;
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+
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+    if (state != cur_state) {
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+        qemu_balloon_inhibit(state);
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+        cur_state = state;
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+    }
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+}
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+
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+/*
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  * At the end of a migration where postcopy_ram_incoming_init was called.
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  */
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 int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
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@@ -429,7 +443,7 @@ int postcopy_ram_incoming_cleanup(MigrationIncomingState *mis)
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         mis->have_fault_thread = false;
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     }
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-    qemu_balloon_inhibit(false);
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+    postcopy_balloon_inhibit(false);
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     if (enable_mlock) {
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         if (os_mlock() < 0) {
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@@ -801,7 +815,7 @@ int postcopy_ram_enable_notify(MigrationIncomingState *mis)
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      * Ballooning can mark pages as absent while we're postcopying
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      * that would cause false userfaults.
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      */
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-    qemu_balloon_inhibit(true);
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+    postcopy_balloon_inhibit(true);
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     trace_postcopy_ram_enable_notify();
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-- 
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1.8.3.1
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