[PATCH v4 1/1] x86/cpu: Make sure flag_is_changeable_p() is always being used

From: Andy Shevchenko
Date: Fri Nov 08 2024 - 09:12:51 EST


When flag_is_changeable_p() is unused, it prevents kernel builds
with clang, `make W=1` and CONFIG_WERROR=y:

arch/x86/kernel/cpu/common.c:351:19: error: unused function 'flag_is_changeable_p' [-Werror,-Wunused-function]
351 | static inline int flag_is_changeable_p(u32 flag)
| ^~~~~~~~~~~~~~~~~~~~

Fix this by moving core around to make sure flag_is_changeable_p() is
always being used.

See also commit 6863f5643dd7 ("kbuild: allow Clang to find unused static
inline functions for W=1 build").

While at it, fix the argument type to be unsigned long, although it currently
only runs in 32-bit cases.

Suggested-by: Dave Hansen <dave.hansen@xxxxxxxxx>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---

v4: fixed the type of parameter (hpa)
v3: rewritten as suggested (Dave)
v2: marked both 32- and 64-bit cases

arch/x86/kernel/cpu/common.c | 33 +++++++++++++++------------------
1 file changed, 15 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index a5f221ea5688..49682e35f9bd 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -276,22 +276,14 @@ static int __init x86_noinvpcid_setup(char *s)
}
early_param("noinvpcid", x86_noinvpcid_setup);

-#ifdef CONFIG_X86_32
-static int cachesize_override = -1;
-static int disable_x86_serial_nr = 1;
-
-static int __init cachesize_setup(char *str)
-{
- get_option(&str, &cachesize_override);
- return 1;
-}
-__setup("cachesize=", cachesize_setup);
-
/* Standard macro to see if a specific flag is changeable */
-static inline int flag_is_changeable_p(u32 flag)
+static inline int flag_is_changeable_p(unsigned long flag)
{
u32 f1, f2;

+ if (!IS_ENABLED(CONFIG_X86_32))
+ return 1;
+
/*
* Cyrix and IDT cpus allow disabling of CPUID
* so the code below may return different results
@@ -316,6 +308,17 @@ static inline int flag_is_changeable_p(u32 flag)
return ((f1^f2) & flag) != 0;
}

+#ifdef CONFIG_X86_32
+static int cachesize_override = -1;
+static int disable_x86_serial_nr = 1;
+
+static int __init cachesize_setup(char *str)
+{
+ get_option(&str, &cachesize_override);
+ return 1;
+}
+__setup("cachesize=", cachesize_setup);
+
/* Probe for the CPUID instruction */
int have_cpuid_p(void)
{
@@ -349,10 +352,6 @@ static int __init x86_serial_nr_setup(char *s)
}
__setup("serialnumber", x86_serial_nr_setup);
#else
-static inline int flag_is_changeable_p(u32 flag)
-{
- return 1;
-}
static inline void squash_the_stupid_serial_number(struct cpuinfo_x86 *c)
{
}
@@ -1088,7 +1087,6 @@ void get_cpu_address_sizes(struct cpuinfo_x86 *c)

static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)
{
-#ifdef CONFIG_X86_32
int i;

/*
@@ -1109,7 +1107,6 @@ static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)
break;
}
}
-#endif
}

#define NO_SPECULATION BIT(0)
--
2.43.0.rc1.1336.g36b5255a03ac