From 30ac483e3c3ffa63b9e92596fa25118e25116438 Mon Sep 17 00:00:00 2001
From: Dario Faggioli <dfaggioli@xxxxxxxx>
Date: Thu, 6 Jan 2022 16:54:18 -0800
Subject: [PATCH 1/4] xen: RCU: bootparam to force quiescence at every call.

Signed-off-by: Dario Faggioli <dfaggioli@xxxxxxxx>
---
 xen/arch/arm/traps.c       |  3 +++
 xen/common/rcupdate.c      | 10 ++++++++++
 xen/include/xen/rcupdate.h |  2 ++
 3 files changed, 15 insertions(+)

diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index 9339d12f58..e2842ba4db 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -87,7 +87,10 @@ static enum {
 static int __init parse_vwfi(const char *s)
 {
 	if ( !strcmp(s, "native") )
+	{
+		rcu_always_quiesc = true;
 		vwfi = NATIVE;
+	}
 	else
 		vwfi = TRAP;
 
diff --git a/xen/common/rcupdate.c b/xen/common/rcupdate.c
index a5a27af3de..7316271da5 100644
--- a/xen/common/rcupdate.c
+++ b/xen/common/rcupdate.c
@@ -95,6 +95,9 @@ struct rcu_data {
     bool            barrier_active;
 };
 
+bool rcu_always_quiesc = false;
+boolean_param("rcu_force_quiesc", rcu_always_quiesc);
+
 /*
  * If a CPU with RCU callbacks queued goes idle, when the grace period is
  * not finished yet, how can we make sure that the callbacks will eventually
@@ -637,6 +640,13 @@ static void rcu_init_percpu_data(int cpu, struct rcu_ctrlblk *rcp,
     rdp->quiescbatch = rcp->completed;
     rdp->qs_pending = 0;
     rdp->cpu = cpu;
+    if ( rcu_always_quiesc )
+    {
+        blimit = INT_MAX;
+        qhimark = 0;
+        qlowmark = 0;
+        //rsinterval = 0;
+    }
     rdp->blimit = blimit;
     init_timer(&rdp->idle_timer, rcu_idle_timer_handler, rdp, cpu);
 }
diff --git a/xen/include/xen/rcupdate.h b/xen/include/xen/rcupdate.h
index 6f2587058e..d279e39022 100644
--- a/xen/include/xen/rcupdate.h
+++ b/xen/include/xen/rcupdate.h
@@ -78,6 +78,8 @@ struct rcu_head {
 } while (0)
 
 
+extern bool rcu_always_quiesc;
+
 int rcu_pending(int cpu);
 int rcu_needs_cpu(int cpu);
 
-- 
2.25.1