linux-kernel - [tip: x86/bugs] x86/bugs: Add attack vector controls for BHI

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Message-ID: <175225017509.406.4120630478925562585.tip-bot2@tip-bot2>
Date: Fri, 11 Jul 2025 16:09:35 -0000
From: "tip-bot2 for David Kaplan" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: David Kaplan <david.kaplan@....com>,
 "Borislav Petkov (AMD)" <bp@...en8.de>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: x86/bugs] x86/bugs: Add attack vector controls for BHI

The following commit has been merged into the x86/bugs branch of tip:

Commit-ID:     ddcd4d3cb37c8ad60cdbaaffe93f85e15e2babb5
Gitweb:        https://git.kernel.org/tip/ddcd4d3cb37c8ad60cdbaaffe93f85e15e2babb5
Author:        David Kaplan <david.kaplan@....com>
AuthorDate:    Mon, 07 Jul 2025 13:33:09 -05:00
Committer:     Borislav Petkov (AMD) <bp@...en8.de>
CommitterDate: Fri, 11 Jul 2025 17:56:41 +02:00

x86/bugs: Add attack vector controls for BHI

Use attack vector controls to determine if BHI mitigation is required.

Signed-off-by: David Kaplan <david.kaplan@....com>
Signed-off-by: Borislav Petkov (AMD) <bp@...en8.de>
Link: https://lore.kernel.org/20250707183316.1349127-15-david.kaplan@amd.com
---
 arch/x86/kernel/cpu/bugs.c | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index ff56251..2022f05 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2217,11 +2217,20 @@ early_param("spectre_bhi", spectre_bhi_parse_cmdline);
 
 static void __init bhi_select_mitigation(void)
 {
-	if (!boot_cpu_has(X86_BUG_BHI) || cpu_mitigations_off())
+	if (!boot_cpu_has(X86_BUG_BHI))
 		bhi_mitigation = BHI_MITIGATION_OFF;
 
-	if (bhi_mitigation == BHI_MITIGATION_AUTO)
-		bhi_mitigation = BHI_MITIGATION_ON;
+	if (bhi_mitigation != BHI_MITIGATION_AUTO)
+		return;
+
+	if (cpu_attack_vector_mitigated(CPU_MITIGATE_GUEST_HOST)) {
+		if (cpu_attack_vector_mitigated(CPU_MITIGATE_USER_KERNEL))
+			bhi_mitigation = BHI_MITIGATION_ON;
+		else
+			bhi_mitigation = BHI_MITIGATION_VMEXIT_ONLY;
+	} else {
+		bhi_mitigation = BHI_MITIGATION_OFF;
+	}
 }
 
 static void __init bhi_update_mitigation(void)