Commit 501bd734 authored by Mateusz Guzik's avatar Mateusz Guzik Committed by Borislav Petkov (AMD)
Browse files

x86/CPU/AMD: Always inline amd_clear_divider() 



The routine is used on syscall exit and on non-AMD CPUs is guaranteed to
be empty.

It probably does not need to be a function call even on CPUs which do need the
mitigation.

  [ bp: Make sure it is always inlined so that noinstr marking works. ]

Signed-off-by: default avatarMateusz Guzik <mjguzik@gmail.com>
Signed-off-by: default avatarBorislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240613082637.659133-1-mjguzik@gmail.com
parent eb9d3c0b

arch/x86/include/asm/processor.h

+11 −1
Original line number Diff line number Diff line
@@ -692,7 +692,17 @@ static inline u32 per_cpu_l2c_id(unsigned int cpu) 


#ifdef CONFIG_CPU_SUP_AMD

extern u32 amd_get_highest_perf(void);

extern void amd_clear_divider(void);



/*

 * Issue a DIV 0/1 insn to clear any division data from previous DIV

 * operations.

 */

static __always_inline void amd_clear_divider(void)

{

	asm volatile(ALTERNATIVE("", "div %2\n\t", X86_BUG_DIV0)

		     :: "a" (0), "d" (0), "r" (1));

}



extern void amd_check_microcode(void);

#else

static inline u32 amd_get_highest_perf(void)		{ return 0; }

arch/x86/kernel/cpu/amd.c

+0 −11
Original line number Diff line number Diff line
@@ -1220,14 +1220,3 @@ void amd_check_microcode(void) 


	on_each_cpu(zenbleed_check_cpu, NULL, 1);

}
 


/*

 * Issue a DIV 0/1 insn to clear any division data from previous DIV

 * operations.

 */

void noinstr amd_clear_divider(void)

{

	asm volatile(ALTERNATIVE("", "div %2\n\t", X86_BUG_DIV0)

		     :: "a" (0), "d" (0), "r" (1));

}

EXPORT_SYMBOL_GPL(amd_clear_divider);