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x86/cpufeatures: Add a IBPB_NO_RET BUG flag

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commit 3ea87dfa31a7b0bb0ff1675e67b9e54883013074 upstream.

Set this flag if the CPU has an IBPB implementation that does not
invalidate return target predictions. Zen generations < 4 do not flush
the RSB when executing an IBPB and this bug flag denotes that.

  [ bp: Massage. ]

Signed-off-by: Johannes Wikner <kwikner@ethz.ch>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Cc: <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Johannes Wikner 2024-09-23 20:49:34 +02:00 committed by Greg Kroah-Hartman
parent 77fa260620
commit c5e57863d7
2 changed files with 5 additions and 0 deletions
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2
arch/x86/include/asm/cpufeatures.h
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@ -456,4 +456,6 @@
#define X86_BUG_SRSO X86_BUG(1*32 + 0) /* AMD SRSO bug */
#define X86_BUG_DIV0 X86_BUG(1*32 + 1) /* AMD DIV0 speculation bug */
#define X86_BUG_RFDS X86_BUG(1*32 + 2) /* CPU is vulnerable to Register File Data Sampling */
#define X86_BUG_BHI X86_BUG(1*32 + 3) /* CPU is affected by Branch History Injection */
#define X86_BUG_IBPB_NO_RET X86_BUG(1*32 + 4) /* "ibpb_no_ret" IBPB omits return target predictions */
#endif /* _ASM_X86_CPUFEATURES_H */

3
arch/x86/kernel/cpu/common.c
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@ -1335,6 +1335,9 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
if (vulnerable_to_rfds(ia32_cap))
setup_force_cpu_bug(X86_BUG_RFDS);
if (cpu_has(c, X86_FEATURE_AMD_IBPB) && !cpu_has(c, X86_FEATURE_AMD_IBPB_RET))
setup_force_cpu_bug(X86_BUG_IBPB_NO_RET);
if (cpu_matches(cpu_vuln_whitelist, NO_MELTDOWN))
return;