x86/bugs: Do not enable IBPB-on-entry when IBPB is not supported

stable inclusion
from stable-v5.10.133
commit 51552b6b52fc865f37ef3ddacd27d807a36695ac
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5PTAS
CVE: CVE-2022-29900,CVE-2022-23816,CVE-2022-29901

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=51552b6b52fc865f37ef3ddacd27d807a36695ac

--------------------------------

commit 2259da15 upstream.

There are some VM configurations which have Skylake model but do not
support IBPB. In those cases, when using retbleed=ibpb, userspace is going
to be killed and kernel is going to panic.

If the CPU does not support IBPB, warn and proceed with the auto option. Also,
do not fallback to IBPB on AMD/Hygon systems if it is not supported.

Fixes: 3ebc1700 ("x86/bugs: Add retbleed=ibpb")
Signed-off-by: NThadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: NBorislav Petkov <bp@suse.de>
Signed-off-by: NBen Hutchings <ben@decadent.org.uk>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NLin Yujun <linyujun809@huawei.com>
Reviewed-by: NZhang Jianhua <chris.zjh@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/x86/kernel/cpu/bugs.c

@@ -821,7 +821,10 @@ static void __init retbleed_select_mitigation(void)
 		break;
 
 	case RETBLEED_CMD_IBPB:
-		if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY)) {
+		if (!boot_cpu_has(X86_FEATURE_IBPB)) {
+			pr_err("WARNING: CPU does not support IBPB.\n");
+			goto do_cmd_auto;
+		} else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY)) {
 			retbleed_mitigation = RETBLEED_MITIGATION_IBPB;
 		} else {
 			pr_err("WARNING: kernel not compiled with CPU_IBPB_ENTRY.\n");
@@ -836,7 +839,7 @@ static void __init retbleed_select_mitigation(void)
 		    boot_cpu_data.x86_vendor == X86_VENDOR_HYGON) {
 			if (IS_ENABLED(CONFIG_CPU_UNRET_ENTRY))
 				retbleed_mitigation = RETBLEED_MITIGATION_UNRET;
-			else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY))
+			else if (IS_ENABLED(CONFIG_CPU_IBPB_ENTRY) && boot_cpu_has(X86_FEATURE_IBPB))
 				retbleed_mitigation = RETBLEED_MITIGATION_IBPB;
 		}