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x86/fred: No ESPFIX needed when FRED is enabled

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Because FRED always restores the full value of %rsp, ESPFIX is
no longer needed when it's enabled.

Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>
Signed-off-by: Xin Li <xin3.li@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Tested-by: Shan Kang <shan.kang@intel.com>
Link: https://lore.kernel.org/r/20231205105030.8698-20-xin3.li@intel.com
This commit is contained in:
H. Peter Anvin (Intel) 2023-12-05 02:50:08 -08:00 committed by Borislav Petkov (AMD)
parent 09794f6893
commit df8838737b
1 changed files with 8 additions and 0 deletions
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8
arch/x86/kernel/espfix_64.c
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@ -106,6 +106,10 @@ void __init init_espfix_bsp(void)
pgd_t *pgd;
p4d_t *p4d;
/* FRED systems always restore the full value of %rsp */
if (cpu_feature_enabled(X86_FEATURE_FRED))
return;
/* Install the espfix pud into the kernel page directory */
pgd = &init_top_pgt[pgd_index(ESPFIX_BASE_ADDR)];
p4d = p4d_alloc(&init_mm, pgd, ESPFIX_BASE_ADDR);
@ -129,6 +133,10 @@ void init_espfix_ap(int cpu)
void *stack_page;
pteval_t ptemask;
/* FRED systems always restore the full value of %rsp */
if (cpu_feature_enabled(X86_FEATURE_FRED))
return;
/* We only have to do this once... */
if (likely(per_cpu(espfix_stack, cpu)))
return; /* Already initialized */