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x86/bugs: Do IBPB fallback check only once

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commit 0fe4aeea9c upstream.

When booting with retbleed=auto, if the kernel wasn't built with
CONFIG_CC_HAS_RETURN_THUNK, the mitigation falls back to IBPB.  Make
sure a warning is printed in that case.  The IBPB fallback check is done
twice, but it really only needs to be done once.

Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Josh Poimboeuf 2022-06-14 15:07:19 -07:00 committed by Greg Kroah-Hartman
parent fd17a42549
commit 469d9b1570
1 changed files with 5 additions and 10 deletions
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15
arch/x86/kernel/cpu/bugs.c
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@ -884,18 +884,13 @@ static void __init retbleed_select_mitigation(void)
case RETBLEED_CMD_AUTO:
default:
if (boot_cpu_data.x86_vendor == X86_VENDOR_AMD ||
boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
if (IS_ENABLED(CONFIG_RETPOLINE) &&
IS_ENABLED(CONFIG_CC_HAS_RETURN_THUNK))
retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
else
retbleed_mitigation = RETBLEED_MITIGATION_IBPB;
}
boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)
retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
/*
* The Intel mitigation (IBRS) was already selected in
* spectre_v2_select_mitigation().
* The Intel mitigation (IBRS or eIBRS) was already selected in
* spectre_v2_select_mitigation(). 'retbleed_mitigation' will
* be set accordingly below.
*/
break;