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Subject[PATCH 3/3] x86: context_tracking: avoid irq_save/irq_restore on kernel entry and exit
Date
x86 always calls user_enter and user_exit with interrupt disabled.
Therefore, it is not necessary to check for exceptions, nor to
save/restore the IRQ state, when context tracking functions are
called by guest_enter and guest_exit.

Use the previously introduced __context_tracking_entry and
__context_tracking_exit.

Cc: Andy Lutomirski <luto@kernel.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/x86/entry/common.c | 4 ++--
include/linux/context_tracking.h | 42 ++++++++++++++++++++++++++--------------
2 files changed, 30 insertions(+), 16 deletions(-)

diff --git a/arch/x86/entry/common.c b/arch/x86/entry/common.c
index 80dcc9261ca3..ba707c6da818 100644
--- a/arch/x86/entry/common.c
+++ b/arch/x86/entry/common.c
@@ -33,7 +33,7 @@
__visible void enter_from_user_mode(void)
{
CT_WARN_ON(ct_state() != CONTEXT_USER);
- user_exit();
+ __user_exit();
}
#endif

@@ -262,7 +262,7 @@ __visible void prepare_exit_to_usermode(struct pt_regs *regs)
local_irq_disable();
}

- user_enter();
+ __user_enter();
}

/*
diff --git a/include/linux/context_tracking.h b/include/linux/context_tracking.h
index 68b575afe5f5..d36a5c8085b7 100644
--- a/include/linux/context_tracking.h
+++ b/include/linux/context_tracking.h
@@ -19,18 +19,6 @@ extern void context_tracking_exit(enum ctx_state state);
extern void context_tracking_user_enter(void);
extern void context_tracking_user_exit(void);

-static inline void user_enter(void)
-{
- if (context_tracking_is_enabled())
- context_tracking_enter(CONTEXT_USER);
-
-}
-static inline void user_exit(void)
-{
- if (context_tracking_is_enabled())
- context_tracking_exit(CONTEXT_USER);
-}
-
static inline enum ctx_state exception_enter(void)
{
enum ctx_state prev_ctx;
@@ -67,13 +55,39 @@ static inline enum ctx_state ct_state(void)
this_cpu_read(context_tracking.state) : CONTEXT_DISABLED;
}
#else
-static inline void user_enter(void) { }
-static inline void user_exit(void) { }
+static inline void __context_tracking_enter(enum ctx_state state) { }
+static inline void __context_tracking_exit(enum ctx_state state) { }
+static inline void context_tracking_enter(enum ctx_state state) { }
+static inline void context_tracking_exit(enum ctx_state state) { }
static inline enum ctx_state exception_enter(void) { return 0; }
static inline void exception_exit(enum ctx_state prev_ctx) { }
static inline enum ctx_state ct_state(void) { return CONTEXT_DISABLED; }
#endif /* !CONFIG_CONTEXT_TRACKING */

+static inline void __user_enter(void)
+{
+ if (context_tracking_is_enabled())
+ __context_tracking_enter(CONTEXT_USER);
+
+}
+static inline void __user_exit(void)
+{
+ if (context_tracking_is_enabled())
+ __context_tracking_exit(CONTEXT_USER);
+}
+
+static inline void user_enter(void)
+{
+ if (context_tracking_is_enabled())
+ context_tracking_enter(CONTEXT_USER);
+
+}
+static inline void user_exit(void)
+{
+ if (context_tracking_is_enabled())
+ context_tracking_exit(CONTEXT_USER);
+}
+
#define CT_WARN_ON(cond) WARN_ON(context_tracking_is_enabled() && (cond))

#ifdef CONFIG_CONTEXT_TRACKING_FORCE
--
2.5.0


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