Commit 558fc8e1 authored by Uros Bizjak's avatar Uros Bizjak Committed by Ingo Molnar
Browse files

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: default avatarUros Bizjak <ubizjak@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Acked-by: default avatarH. Peter Anvin <hpa@zytor.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Nick Desaulniers <ndesaulniers@google.com>
Link: https://lore.kernel.org/r/20250307091022.181136-1-ubizjak@gmail.com
parent 9c94c14c

arch/x86/boot/cpuflags.c

+9 −17
Original line number Diff line number Diff line
@@ -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)

{

arch/x86/boot/cpuflags.h

+5 −1
Original line number Diff line number Diff line
@@ -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);