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x86/CPU/AMD: Always inline amd_clear_divider()

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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: Mateusz Guzik <mjguzik@gmail.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240613082637.659133-1-mjguzik@gmail.com
This commit is contained in:
Mateusz Guzik 2024-06-13 10:26:37 +02:00 committed by Borislav Petkov (AMD)
parent eb9d3c0bb0
commit 501bd734f9
2 changed files with 11 additions and 12 deletions
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12
arch/x86/include/asm/processor.h
View File

@ -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; }

11
arch/x86/kernel/cpu/amd.c
View File

@ -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);