From: David Woodhouse <dwmw2@infradead.org>
To: peterz@infradead.org, mhillenb@amazon.de,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
paulmck@linux.vnet.ibm.com
Subject: [PATCH v2] kvm/x86: Inform RCU of quiescent state when entering guest mode
Date: Wed, 11 Jul 2018 19:01:01 +0100 [thread overview]
Message-ID: <20180711180101.3711464-1-dwmw2@infradead.org> (raw)
In-Reply-To: <20180711174843.GX3593@linux.vnet.ibm.com>
From: David Woodhouse <dwmw@amazon.co.uk>
RCU can spend long periods of time waiting for a CPU which is actually in
KVM guest mode, entirely pointlessly. Treat it like the idle and userspace
modes, and don't wait for it.
Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
---
arch/x86/kvm/x86.c | 2 ++
include/linux/rcupdate.h | 7 +++++++
kernel/rcu/tree.c | 2 ++
3 files changed, 11 insertions(+)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0046aa70205a..b0c82f70afa7 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -7458,7 +7458,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
vcpu->arch.switch_db_regs &= ~KVM_DEBUGREG_RELOAD;
}
+ rcu_kvm_enter();
kvm_x86_ops->run(vcpu);
+ rcu_kvm_exit();
/*
* Do this here before restoring debug registers on the host. And
diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 65163aa0bb04..1325f9d9ce00 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -212,6 +212,13 @@ do { \
#error "Unknown RCU implementation specified to kernel configuration"
#endif
+/*
+ * These are currently identical to the _idle_ versions but let's
+ * explicitly have separate copies to keep Paul honest in future.
+ */
+static inline void rcu_kvm_enter(void) { rcu_idle_enter(); }
+static inline void rcu_kvm_exit(void) { rcu_idle_exit(); }
+
/*
* The init_rcu_head_on_stack() and destroy_rcu_head_on_stack() calls
* are needed for dynamic initialization and destruction of rcu_head
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index aa7cade1b9f3..d38c381bf4e3 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -760,6 +760,7 @@ void rcu_idle_enter(void)
lockdep_assert_irqs_disabled();
rcu_eqs_enter(false);
}
+EXPORT_SYMBOL_GPL(rcu_idle_enter);
#ifdef CONFIG_NO_HZ_FULL
/**
@@ -913,6 +914,7 @@ void rcu_idle_exit(void)
rcu_eqs_exit(false);
local_irq_restore(flags);
}
+EXPORT_SYMBOL_GPL(rcu_idle_exit);
#ifdef CONFIG_NO_HZ_FULL
/**
--
2.17.1
next prev parent reply other threads:[~2018-07-11 18:01 UTC|newest]
Thread overview: 93+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-06 14:53 [RFC] Make need_resched() return true when rcu_urgent_qs requested David Woodhouse
2018-07-06 16:29 ` Peter Zijlstra
2018-07-06 17:11 ` Paul E. McKenney
2018-07-06 17:14 ` David Woodhouse
2018-07-06 21:12 ` Paul E. McKenney
2018-07-09 8:58 ` Peter Zijlstra
2018-07-09 8:53 ` Peter Zijlstra
2018-07-09 9:18 ` David Woodhouse
2018-07-09 10:44 ` Peter Zijlstra
2018-07-09 10:56 ` David Woodhouse
2018-07-09 11:06 ` Peter Zijlstra
2018-07-09 11:12 ` David Woodhouse
2018-07-09 11:31 ` Peter Zijlstra
2018-07-09 12:34 ` Paul E. McKenney
2018-07-09 12:47 ` David Woodhouse
2018-07-09 14:30 ` Paul E. McKenney
2018-07-09 12:55 ` Peter Zijlstra
2018-07-09 12:57 ` David Woodhouse
2018-07-09 13:02 ` Peter Zijlstra
2018-07-09 14:29 ` Paul E. McKenney
2018-07-09 14:43 ` Peter Zijlstra
2018-07-09 14:54 ` Paul E. McKenney
2018-07-09 15:26 ` Peter Zijlstra
2018-07-09 16:34 ` Paul E. McKenney
2018-07-09 16:44 ` Paul E. McKenney
2018-07-09 18:50 ` David Woodhouse
2018-07-09 20:34 ` Paul E. McKenney
2018-07-09 20:35 ` David Woodhouse
2018-07-09 20:42 ` Paul E. McKenney
2018-07-09 20:45 ` David Woodhouse
2018-07-09 21:05 ` Paul E. McKenney
2018-07-09 22:08 ` Paul E. McKenney
2018-07-11 10:57 ` David Woodhouse
2018-07-11 12:51 ` Paul E. McKenney
2018-07-11 12:58 ` David Woodhouse
2018-07-11 14:25 ` Paul E. McKenney
2018-07-11 14:23 ` David Woodhouse
2018-07-11 14:43 ` Paul E. McKenney
2018-07-11 16:49 ` Paul E. McKenney
2018-07-11 17:03 ` David Woodhouse
2018-07-11 17:48 ` Paul E. McKenney
2018-07-11 18:01 ` David Woodhouse [this message]
2018-07-11 18:20 ` [PATCH v2] kvm/x86: Inform RCU of quiescent state when entering guest mode Paul E. McKenney
2018-07-11 18:36 ` Paul E. McKenney
2018-07-11 18:39 ` Christian Borntraeger
2018-07-11 20:27 ` Paul E. McKenney
2018-07-11 20:54 ` David Woodhouse
2018-07-11 21:09 ` Paul E. McKenney
2018-07-11 21:11 ` Christian Borntraeger
2018-07-11 21:32 ` Paul E. McKenney
2018-07-11 21:39 ` Christian Borntraeger
2018-07-11 23:47 ` Paul E. McKenney
2018-07-12 8:31 ` David Woodhouse
2018-07-12 11:00 ` Christian Borntraeger
2018-07-12 11:10 ` David Woodhouse
2018-07-12 11:58 ` Christian Borntraeger
2018-07-12 12:04 ` Christian Borntraeger
2018-07-11 23:37 ` Paul E. McKenney
2018-07-12 2:15 ` Paul E. McKenney
2018-07-12 6:21 ` Christian Borntraeger
2018-07-12 9:52 ` David Woodhouse
2018-07-11 18:31 ` [RFC] Make need_resched() return true when rcu_urgent_qs requested Christian Borntraeger
2018-07-11 20:17 ` Paul E. McKenney
2018-07-11 20:19 ` David Woodhouse
2018-07-11 21:08 ` Paul E. McKenney
2018-07-12 12:00 ` David Woodhouse
2018-07-12 12:53 ` Paul E. McKenney
2018-07-12 16:17 ` Paul E. McKenney
2018-07-16 15:40 ` Paul E. McKenney
2018-07-17 8:19 ` David Woodhouse
2018-07-17 12:56 ` Paul E. McKenney
2018-07-18 15:36 ` Paul E. McKenney
2018-07-18 16:01 ` David Woodhouse
2018-07-18 16:37 ` Paul E. McKenney
2018-07-18 19:41 ` David Woodhouse
2018-07-18 20:17 ` Paul E. McKenney
2018-07-19 0:26 ` Frederic Weisbecker
2018-07-19 6:45 ` Christian Borntraeger
2018-07-19 7:20 ` David Woodhouse
2018-07-19 10:23 ` Christian Borntraeger
2018-07-19 12:55 ` Paul E. McKenney
2018-07-19 13:14 ` Frederic Weisbecker
2018-07-19 13:36 ` David Woodhouse
2018-07-19 17:09 ` Paul E. McKenney
2018-07-23 8:08 ` David Woodhouse
2018-07-23 12:22 ` Paul E. McKenney
2018-07-19 0:32 ` Frederic Weisbecker
2018-07-19 3:11 ` Paul E. McKenney
2018-07-19 6:16 ` David Woodhouse
2018-07-19 13:17 ` Frederic Weisbecker
2018-07-19 13:15 ` Frederic Weisbecker
2018-07-10 9:24 ` Peter Zijlstra
2018-07-10 16:26 ` Paul E. McKenney
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