On Wed, Jun 24, 2026 at 05:59:19AM -0700, Sean Christopherson wrote:

On Tue, Jun 23, 2026, Pawan Gupta wrote:

quoted

There is EXPORT_STATIC_CALL_TRAMP() that hides the static key from all
modules. But there is no equivalent of EXPORT_SYMBOL_FOR_MODULES() to
restrict symbol visibility to only certain modules.

Add EXPORT_STATIC_CALL_FOR_MODULES(name, mods) that wraps both the key and
the trampoline with EXPORT_SYMBOL_FOR_MODULES(), allowing only a limited
set of modules to see and update the static key.

The immediate user is KVM, in the following commit.

checkpatch reported below warnings with this change that I believe don't
apply in this case:

  include/linux/static_call.h:219: WARNING: Non-declarative macros with multiple statements should be enclosed in a do - while loop
  include/linux/static_call.h:220: WARNING: EXPORT_SYMBOL(foo); should immediately follow its function/variable

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
---
 include/linux/static_call.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/static_call.h b/include/linux/static_call.h
index 78a77a4ae0ea..b610afd1ed55 100644
--- a/include/linux/static_call.h
+++ b/include/linux/static_call.h

@@ -216,6 +216,9 @@ extern long __static_call_return0(void);
 #define EXPORT_STATIC_CALL_GPL(name)					\
 	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name));			\
 	EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name))
+#define EXPORT_STATIC_CALL_FOR_MODULES(name, mods)			\
+	EXPORT_SYMBOL_FOR_MODULES(STATIC_CALL_KEY(name), mods);		\
+	EXPORT_SYMBOL_FOR_MODULES(STATIC_CALL_TRAMP(name), mods)
 
 /* Leave the key unexported, so modules can't change static call targets: */
 #define EXPORT_STATIC_CALL_TRAMP(name)					\

@@ -276,6 +279,9 @@ extern long __static_call_return0(void);
 #define EXPORT_STATIC_CALL_GPL(name)					\
 	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name));			\
 	EXPORT_SYMBOL_GPL(STATIC_CALL_TRAMP(name))
+#define EXPORT_STATIC_CALL_FOR_MODULES(name, mods)			\
+	EXPORT_SYMBOL_FOR_MODULES(STATIC_CALL_KEY(name), mods);		\
+	EXPORT_SYMBOL_FOR_MODULES(STATIC_CALL_TRAMP(name), mods)
 
 /* Leave the key unexported, so modules can't change static call targets: */
 #define EXPORT_STATIC_CALL_TRAMP(name)					\

@@ -346,6 +352,8 @@ static inline int static_call_text_reserved(void *start, void *end)
 
 #define EXPORT_STATIC_CALL(name)	EXPORT_SYMBOL(STATIC_CALL_KEY(name))
 #define EXPORT_STATIC_CALL_GPL(name)	EXPORT_SYMBOL_GPL(STATIC_CALL_KEY(name))
+#define EXPORT_STATIC_CALL_FOR_MODULES(name, mods)			\
+	EXPORT_SYMBOL_FOR_MODULES(STATIC_CALL_KEY(name), mods)
 
 #endif /* CONFIG_HAVE_STATIC_CALL */

Drat, I forgot about this.  Exporting static call trampolines for KVM came up in
another conversation[*].  I had already put together patches to effectively default
to exporting only the trampoline, and also to deduplicate this code so that the
CONFIG_HAVE_STATIC_CALL_INLINE=y / CONFIG_HAVE_STATIC_CALL=y / CONFIG_HAVE_STATIC_CALL=n
implementations don't need to copy+paste the same lines of code.

The attached patches touch a lot more code, and will conflict mightily with KVM
changes I want to land in 7.3 (more use of a static_call in KVM).  But if we get
them applied (to tip tree) shortly after 7.2-rc1 and provide a topic branch/tag,
then there shouldn't be too much juggling needed?

If we want to go with the more aggressive cleanup, I'll formally post the patches.

[*] https://lore.kernel.org/all/ahhoDGUz39KSGZ6o@google.com (local)

Thanks for the context.

Earlier making the key ro-after-init came up as an option in a thread with
Peter. Does it look like a good option to you?

diff --git a/include/linux/static_call.h b/include/linux/static_call.h
index b610afd1ed55..ea56da8fb446 100644
--- a/include/linux/static_call.h
+++ b/include/linux/static_call.h

@@ -200,6 +200,14 @@ extern long __static_call_return0(void);
 	};								\
 	ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name)
 
+#define DEFINE_STATIC_CALL_NULL_RO_AFTER_INIT(name, _func)		\
+	DECLARE_STATIC_CALL(name, _func);				\
+	struct static_call_key STATIC_CALL_KEY(name) __ro_after_init = {\
+		.func = _func,						\
+		.type = 1,						\
+	};								\
+	ARCH_DEFINE_STATIC_CALL_NULL_TRAMP(name)
+
 #define DEFINE_STATIC_CALL_RET0(name, _func)				\
 	DECLARE_STATIC_CALL(name, _func);				\
 	struct static_call_key STATIC_CALL_KEY(name) = {		\