Re: [PATCH] KVM: allow host header to be included even for !CONFIG_KVM

[Frederic Weisbecker <fweisbec@gmail.com>]

On Fri, May 17, 2013 at 07:09:42AM -0700, Kevin Hilman wrote:
> Frederic Weisbecker <fweisbec@gmail.com> writes:
> 
> > On Thu, May 16, 2013 at 12:52:03AM +0200, Frederic Weisbecker wrote:
> >> On Mon, Mar 25, 2013 at 02:14:20PM -0700, Kevin Hilman wrote:
> >> > Gleb Natapov <gleb@redhat.com> writes:
> >> > 
> >> > > On Sun, Mar 24, 2013 at 02:44:26PM +0100, Frederic Weisbecker wrote:
> >> > >> 2013/3/21 Gleb Natapov <gleb@redhat.com>:
> >> > >> > Isn't is simpler for kernel/context_tracking.c to define empty
> >> > >> > __guest_enter()/__guest_exit() if !CONFIG_KVM.
> >> > >> 
> >> > >> That doesn't look right. Off-cases are usually handled from the
> >> > >> headers, right? So that we avoid iffdeffery ugliness in core code.
> >> > > Lets put it in linux/context_tracking.h header then.
> >> > 
> >> > Here's a version to do that.
> >> > 
> >> > Kevin
> >> > 
> >> > From d9d909394479dd7ff90b7bddb95a564945406719 Mon Sep 17 00:00:00 2001
> >> > From: Kevin Hilman <khilman@linaro.org>
> >> > Date: Mon, 25 Mar 2013 14:12:41 -0700
> >> > Subject: [PATCH v2] ontext_tracking: fix !CONFIG_KVM compile: add stub guest
> >> >  enter/exit
> >> 
> >> Sorry for my very delayed response...
> >> 
> >> > 
> >> > When KVM is not enabled, or not available on a platform, the KVM
> >> > headers should not be included.  Instead, just define stub
> >> > __guest_[enter|exit] functions.
> >> 
> >> May be it would be cleaner to move guest_enter/exit definitions altogether
> >> in linux/context_tracking.h
> >> 
> >> After all that's where the implementation mostly belong to.
> >> 
> >> Let me see if I can get that in shape.
> >
> > Does the following work for you?
> 
> Nope. 
> 
> Since it still includs kvm_host.h on non-KVM builds, there is potential
> for problems.  For example, on ARM (v3.10-rc1 + this patch) has this
> build error:
> 
>   CC      kernel/context_tracking.o
> In file included from /work/kernel/linaro/nohz/arch/arm/include/asm/kvm_host.h:41:0,
>                  from /work/kernel/linaro/nohz/include/linux/kvm_host.h:34,
>                  from /work/kernel/linaro/nohz/kernel/context_tracking.c:18:
> /work/kernel/linaro/nohz/arch/arm/include/asm/kvm_vgic.h:38:6: warning: "CONFIG_KVM_ARM_MAX_VCPUS" is not defined [-Wundef]
> In file included from /work/kernel/linaro/nohz/arch/arm/include/asm/kvm_host.h:41:0,
>                  from /work/kernel/linaro/nohz/include/linux/kvm_host.h:34,
>                  from /work/kernel/linaro/nohz/kernel/context_tracking.c:18:
> /work/kernel/linaro/nohz/arch/arm/include/asm/kvm_vgic.h:59:11: error: 'CONFIG_KVM_ARM_MAX_VCPUS' undeclared here (not in a function)

Sorry I forgot to remove the include to kvm_host.h in context_tracking.c,
here's the fixed patch:

diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 365f4a6..fc09d7b 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -3,6 +3,7 @@
 
 #include <linux/sched.h>
 #include <linux/percpu.h>
+#include <linux/vtime.h>
 #include <asm/ptrace.h>
 
 struct context_tracking {
@@ -19,6 +20,26 @@ struct context_tracking {
 	} state;
 };
 
+static inline void __guest_enter(void)
+{
+	/*
+	 * This is running in ioctl context so we can avoid
+	 * the call to vtime_account() with its unnecessary idle check.
+	 */
+	vtime_account_system(current);
+	current->flags |= PF_VCPU;
+}
+
+static inline void __guest_exit(void)
+{
+	/*
+	 * This is running in ioctl context so we can avoid
+	 * the call to vtime_account() with its unnecessary idle check.
+	 */
+	vtime_account_system(current);
+	current->flags &= ~PF_VCPU;
+}
+
 #ifdef CONFIG_CONTEXT_TRACKING
 DECLARE_PER_CPU(struct context_tracking, context_tracking);
 
@@ -35,6 +56,9 @@ static inline bool context_tracking_active(void)
 extern void user_enter(void);
 extern void user_exit(void);
 
+extern void guest_enter(void);
+extern void guest_exit(void);
+
 static inline enum ctx_state exception_enter(void)
 {
 	enum ctx_state prev_ctx;
@@ -57,6 +81,17 @@ extern void context_tracking_task_switch(struct task_struct *prev,
 static inline bool context_tracking_in_user(void) { return false; }
 static inline void user_enter(void) { }
 static inline void user_exit(void) { }
+
+static inline void guest_enter(void)
+{
+	__guest_enter();
+}
+
+static inline void guest_exit(void)
+{
+	__guest_exit();
+}
+
 static inline enum ctx_state exception_enter(void) { return 0; }
 static inline void exception_exit(enum ctx_state prev_ctx) { }
 static inline void context_tracking_task_switch(struct task_struct *prev,
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
index f0eea07..8db53cf 100644
--- a/include/linux/kvm_host.h
+++ b/include/linux/kvm_host.h
@@ -23,6 +23,7 @@
 #include <linux/ratelimit.h>
 #include <linux/err.h>
 #include <linux/irqflags.h>
+#include <linux/context_tracking.h>
 #include <asm/signal.h>
 
 #include <linux/kvm.h>
@@ -760,42 +761,6 @@ static inline int kvm_iommu_unmap_guest(struct kvm *kvm)
 }
 #endif
 
-static inline void __guest_enter(void)
-{
-	/*
-	 * This is running in ioctl context so we can avoid
-	 * the call to vtime_account() with its unnecessary idle check.
-	 */
-	vtime_account_system(current);
-	current->flags |= PF_VCPU;
-}
-
-static inline void __guest_exit(void)
-{
-	/*
-	 * This is running in ioctl context so we can avoid
-	 * the call to vtime_account() with its unnecessary idle check.
-	 */
-	vtime_account_system(current);
-	current->flags &= ~PF_VCPU;
-}
-
-#ifdef CONFIG_CONTEXT_TRACKING
-extern void guest_enter(void);
-extern void guest_exit(void);
-
-#else /* !CONFIG_CONTEXT_TRACKING */
-static inline void guest_enter(void)
-{
-	__guest_enter();
-}
-
-static inline void guest_exit(void)
-{
-	__guest_exit();
-}
-#endif /* !CONFIG_CONTEXT_TRACKING */
-
 static inline void kvm_guest_enter(void)
 {
 	unsigned long flags;
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 65349f0..85bdde1 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -15,7 +15,6 @@
  */
 
 #include <linux/context_tracking.h>
-#include <linux/kvm_host.h>
 #include <linux/rcupdate.h>
 #include <linux/sched.h>
 #include <linux/hardirq.h>