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From: riel@redhat.com
To: kvm@vger.kernel.org
Cc: borntraeger@de.ibm.com, linux-kernel@vger.kernel.org,
	mtosatti@redhat.com, mingo@kernel.orgm, ak@linux.intel.com,
	oleg@redhat.com, masami.hiramatsu.pt@hitachi.com,
	fweisbec@gmail.com, paulmck@linux.vnet.ibm.com,
	lcapitulino@redhat.com, pbonzini@redhat.com
Subject: [PATCH 4/5] kvm,rcu,nohz: use RCU extended quiescent state when running KVM guest
Date: Thu,  5 Feb 2015 15:23:51 -0500	[thread overview]
Message-ID: <1423167832-17609-5-git-send-email-riel@redhat.com> (raw)
In-Reply-To: <1423167832-17609-1-git-send-email-riel@redhat.com>

From: Rik van Riel <riel@redhat.com>

The host kernel is not doing anything while the CPU is executing
a KVM guest VCPU, so it can be marked as being in an extended
quiescent state, identical to that used when running user space
code.

The only exception to that rule is when the host handles an
interrupt, which is already handled by the irq code, which
calls rcu_irq_enter and rcu_irq_exit.

The guest_enter and guest_exit functions already switch vtime
accounting independent of context tracking, so leave those calls
where they are, instead of moving them into the context tracking
code.

Signed-off-by: Rik van Riel <riel@redhat.com>
---
 include/linux/context_tracking.h       | 8 +++++++-
 include/linux/context_tracking_state.h | 1 +
 include/linux/kvm_host.h               | 3 ++-
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index bd9f000fc98d..a5d3bb44b897 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -43,7 +43,7 @@ static inline enum ctx_state exception_enter(void)
 static inline void exception_exit(enum ctx_state prev_ctx)
 {
 	if (context_tracking_is_enabled()) {
-		if (prev_ctx == IN_USER)
+		if (prev_ctx == IN_USER || prev_ctx == IN_GUEST)
 			context_tracking_user_enter(prev_ctx);
 	}
 }
@@ -78,6 +78,9 @@ static inline void guest_enter(void)
 		vtime_guest_enter(current);
 	else
 		current->flags |= PF_VCPU;
+
+	if (context_tracking_is_enabled())
+		context_tracking_user_enter(IN_GUEST);
 }
 
 static inline void guest_exit(void)
@@ -86,6 +89,9 @@ static inline void guest_exit(void)
 		vtime_guest_exit(current);
 	else
 		current->flags &= ~PF_VCPU;
+
+	if (context_tracking_is_enabled())
+		context_tracking_user_exit(IN_GUEST);
 }
 
 #else
diff --git a/include/linux/context_tracking_state.h b/include/linux/context_tracking_state.h
index 97a81225d037..f3ef027af749 100644
--- a/include/linux/context_tracking_state.h
+++ b/include/linux/context_tracking_state.h
@@ -15,6 +15,7 @@ struct context_tracking {
 	enum ctx_state {
 		IN_KERNEL = 0,
 		IN_USER,
+		IN_GUEST,
 	} state;
 };
 
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index 26f106022c88..c7828a6a9614 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -772,7 +772,8 @@ static inline void kvm_guest_enter(void)
 	 * one time slice). Lets treat guest mode as quiescent state, just like
 	 * we do with user-mode execution.
 	 */
-	rcu_virt_note_context_switch(smp_processor_id());
+	if (!context_tracking_cpu_is_enabled())
+		rcu_virt_note_context_switch(smp_processor_id());
 }
 
 static inline void kvm_guest_exit(void)
-- 
1.9.3


  parent reply	other threads:[~2015-02-05 20:24 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-05 20:23 [PATCH v2 0/5] rcu,nohz,kvm: " riel
2015-02-05 20:23 ` [PATCH 1/5] rcu,nohz: add state parameter to context_tracking_user_enter/exit riel
2015-02-05 23:55   ` Paul E. McKenney
2015-02-06 10:15     ` Paolo Bonzini
2015-02-06 13:41       ` Paul E. McKenney
2015-02-06 17:22   ` Frederic Weisbecker
2015-02-06 18:20     ` Rik van Riel
2015-02-06 18:23       ` Frederic Weisbecker
2015-02-06 18:51         ` Rik van Riel
2015-02-06 23:15           ` Frederic Weisbecker
2015-02-07  3:53             ` Rik van Riel
2015-02-07  6:34               ` Paul E. McKenney
2015-02-07  7:14                 ` Paul E. McKenney
2015-02-07  8:30                   ` Frederic Weisbecker
2015-02-07 11:29                     ` Rik van Riel
2015-02-07 20:06                     ` Paul E. McKenney
2015-02-09 15:42                       ` Rik van Riel
2015-02-05 20:23 ` [PATCH 2/5] rcu,nohz: run vtime_user_enter/exit only when state == IN_USER riel
2015-02-05 20:23 ` [PATCH 3/5] nohz,kvm: export context_tracking_user_enter/exit riel
2015-02-05 23:55   ` Paul E. McKenney
2015-02-05 20:23 ` riel [this message]
2015-02-05 23:56   ` [PATCH 4/5] kvm,rcu,nohz: use RCU extended quiescent state when running KVM guest Paul E. McKenney
2015-02-06 18:01   ` Frederic Weisbecker
2015-02-06 23:24   ` Frederic Weisbecker
2015-02-05 20:23 ` [PATCH 5/5] nohz: add stub context_tracking_is_enabled riel
2015-02-05 23:56   ` Paul E. McKenney
2015-02-06 13:46 ` [PATCH v2 0/5] rcu,nohz,kvm: use RCU extended quiescent state when running KVM guest Frederic Weisbecker
2015-02-06 13:50   ` Paolo Bonzini
2015-02-06 16:19     ` Paul E. McKenney
2015-02-06 18:09     ` Frederic Weisbecker
2015-02-06 14:56   ` Rik van Riel
2015-02-06 18:05     ` Frederic Weisbecker
2015-02-06 15:00 ` Christian Borntraeger
2015-02-06 18:20   ` Frederic Weisbecker

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