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UPSTREAM: x86/speculation: Use generic retpoline by default on AMD

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commit 244d00b5dd upstream.

AMD retpoline may be susceptible to speculation. The speculation
execution window for an incorrect indirect branch prediction using
LFENCE/JMP sequence may potentially be large enough to allow
exploitation using Spectre V2.

By default, don't use retpoline,lfence on AMD.  Instead, use the
generic retpoline.

Bug: 215557547
Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ia055414ec9ab24eeebb21e799cc220cce8a1f3f6
This commit is contained in:
Kim Phillips
2022-02-28 11:23:15 -06:00
committed by Greg Kroah-Hartman
parent bd02dc4329
commit c4188388a3
1 changed files with 0 additions and 9 deletions
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9
arch/x86/kernel/cpu/bugs.c
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@@ -904,15 +904,6 @@ static enum spectre_v2_mitigation __init spectre_v2_select_retpoline(void)
return SPECTRE_V2_NONE;
}
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
if (!boot_cpu_has(X86_FEATURE_LFENCE_RDTSC)) {
pr_err("LFENCE not serializing, switching to generic retpoline\n");
return SPECTRE_V2_RETPOLINE;
}
return SPECTRE_V2_LFENCE;
}
return SPECTRE_V2_RETPOLINE;
}