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x86/fault: Skip the AMD erratum #91 workaround on unaffected CPUs

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According to the Revision Guide for AMD Athlon™ 64 and AMD Opteron™
Processors, only early revisions of family 0xF are affected. This will
avoid unnecessarily fetching instruction bytes before sending SIGSEGV to
user programs.

Signed-off-by: Andy Lutomirski <luto@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: https://lkml.kernel.org/r/477173b7784bc28afb3e53d76ae5ef143917e8dd.1612924255.git.luto@kernel.org
This commit is contained in:
Andy Lutomirski 2021-02-09 18:33:34 -08:00 committed by Borislav Petkov
parent 35f1c89b0c
commit d24df8ecf9
1 changed files with 13 additions and 0 deletions
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13
arch/x86/mm/fault.c
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@ -106,6 +106,15 @@ check_prefetch_opcode(struct pt_regs *regs, unsigned char *instr,
}
}
static bool is_amd_k8_pre_npt(void)
{
struct cpuinfo_x86 *c = &boot_cpu_data;
return unlikely(IS_ENABLED(CONFIG_CPU_SUP_AMD) &&
c->x86_vendor == X86_VENDOR_AMD &&
c->x86 == 0xf && c->x86_model < 0x40);
}
static int
is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
{
@ -113,6 +122,10 @@ is_prefetch(struct pt_regs *regs, unsigned long error_code, unsigned long addr)
unsigned char *instr;
int prefetch = 0;
/* Erratum #91 affects AMD K8, pre-NPT CPUs */
if (!is_amd_k8_pre_npt())
return 0;
/*
* If it was a exec (instruction fetch) fault on NX page, then
* do not ignore the fault: