[PATCH v3 5/6] percpu: Repurpose __percpu tag as a named address space qualifier

Uros Bizjak
2024-12-08T20:47:32Z

The patch introduces __percpu_qual define and repurposes __percpu
tag as a named address space qualifier using the new define.

Arches can now conditionally define __percpu_qual as their
named address space qualifier for percpu variables.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Acked-by: Nadav Amit <nadav.amit@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Dennis Zhou <dennis@kernel.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>
---
v3: - Rename __per_cpu_qual to __percpu_qual.
---
include/asm-generic/percpu.h | 13 +++++++++++++
include/linux/compiler_types.h | 2 +-
2 files changed, 14 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h
index 50597b975a49..02aeca21479a 100644
--- a/include/asm-generic/percpu.h
+++ b/include/asm-generic/percpu.h
@@ -6,6 +6,19 @@
#include <linux/threads.h>
#include <linux/percpu-defs.h>

+/*
+ * __percpu_qual is the qualifier for the percpu named address space.
+ *
+ * Most arches use generic named address space for percpu variables but
+ * some arches define percpu variables in different named address space
+ * (on the x86 arch, percpu variable may be declared as being relative
+ * to the %fs or %gs segments using __seg_fs or __seg_gs named address
+ * space qualifier).
+ */
+#ifndef __percpu_qual
+# define __percpu_qual
+#endif
+
#ifdef CONFIG_SMP

/*
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 981cc3d7e3aa..5d6544545658 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -57,7 +57,7 @@ static inline void __chk_io_ptr(const volatile void __iomem *ptr) { }
# define __user BTF_TYPE_TAG(user)
# endif
# define __iomem
-# define __percpu BTF_TYPE_TAG(percpu)
+# define __percpu __percpu_qual BTF_TYPE_TAG(percpu)
# define __rcu BTF_TYPE_TAG(rcu)

# define __chk_user_ptr(x) (void)0
--
2.42.0