From 558fc8e1869ca6e1eb99a1e2b52f6c35424d4adf Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Fri, 7 Mar 2025 10:10:03 +0100 Subject: [PATCH] x86/boot: Do not test if AC and ID eflags are changeable on x86_64 The test for the changeabitily of AC and ID EFLAGS is used to distinguish between i386 and i486 processors (AC) and to test for CPUID instruction support (ID). Skip these tests on x86_64 processors as they always supports CPUID. Also change the return type of has_eflag() to bool. Signed-off-by: Uros Bizjak Signed-off-by: Ingo Molnar Acked-by: H. Peter Anvin Cc: Linus Torvalds Cc: Brian Gerst Cc: Nathan Chancellor Cc: Nick Desaulniers Link: https://lore.kernel.org/r/20250307091022.181136-1-ubizjak@gmail.com --- arch/x86/boot/cpuflags.c | 26 +++++++++----------------- arch/x86/boot/cpuflags.h | 6 +++++- 2 files changed, 14 insertions(+), 18 deletions(-) diff --git a/arch/x86/boot/cpuflags.c b/arch/x86/boot/cpuflags.c index d75237ba7ce94..2150a016176f2 100644 --- a/arch/x86/boot/cpuflags.c +++ b/arch/x86/boot/cpuflags.c @@ -29,40 +29,32 @@ static int has_fpu(void) return fsw == 0 && (fcw & 0x103f) == 0x003f; } +#ifdef CONFIG_X86_32 /* * For building the 16-bit code we want to explicitly specify 32-bit * push/pop operations, rather than just saying 'pushf' or 'popf' and - * letting the compiler choose. But this is also included from the - * compressed/ directory where it may be 64-bit code, and thus needs - * to be 'pushfq' or 'popfq' in that case. + * letting the compiler choose. */ -#ifdef __x86_64__ -#define PUSHF "pushfq" -#define POPF "popfq" -#else -#define PUSHF "pushfl" -#define POPF "popfl" -#endif - -int has_eflag(unsigned long mask) +bool has_eflag(unsigned long mask) { unsigned long f0, f1; - asm volatile(PUSHF " \n\t" - PUSHF " \n\t" + asm volatile("pushfl \n\t" + "pushfl \n\t" "pop %0 \n\t" "mov %0,%1 \n\t" "xor %2,%1 \n\t" "push %1 \n\t" - POPF " \n\t" - PUSHF " \n\t" + "popfl \n\t" + "pushfl \n\t" "pop %1 \n\t" - POPF + "popfl" : "=&r" (f0), "=&r" (f1) : "ri" (mask)); return !!((f0^f1) & mask); } +#endif void cpuid_count(u32 id, u32 count, u32 *a, u32 *b, u32 *c, u32 *d) { diff --git a/arch/x86/boot/cpuflags.h b/arch/x86/boot/cpuflags.h index fdcc2aa4c3c4a..a398d9204ad00 100644 --- a/arch/x86/boot/cpuflags.h +++ b/arch/x86/boot/cpuflags.h @@ -15,7 +15,11 @@ struct cpu_features { extern struct cpu_features cpu; extern u32 cpu_vendor[3]; -int has_eflag(unsigned long mask); +#ifdef CONFIG_X86_32 +bool has_eflag(unsigned long mask); +#else +static inline bool has_eflag(unsigned long mask) { return true; } +#endif void get_cpuflags(void); void cpuid_count(u32 id, u32 count, u32 *a, u32 *b, u32 *c, u32 *d); bool has_cpuflag(int flag);