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Message-ID: <20250310164023.779191-21-david.kaplan@amd.com>
Date: Mon, 10 Mar 2025 11:40:07 -0500
From: David Kaplan <david.kaplan@....com>
To: Thomas Gleixner <tglx@...utronix.de>, Borislav Petkov <bp@...en8.de>,
Peter Zijlstra <peterz@...radead.org>, Josh Poimboeuf <jpoimboe@...nel.org>,
Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>, Ingo Molnar
<mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
<x86@...nel.org>, "H . Peter Anvin" <hpa@...or.com>
CC: <linux-kernel@...r.kernel.org>, Brendan Jackman <jackmanb@...gle.com>,
Derek Manwaring <derekmn@...zon.com>
Subject: [PATCH v4 20/36] x86/bugs: Determine relevant vulnerabilities based on attack vector controls.
The function should_mitigate_vuln() defines which vulnerabilities should
be mitigated based on the selected attack vector controls. The
selections here are based on the individual characteristics of each
vulnerability.
Signed-off-by: David Kaplan <david.kaplan@....com>
---
arch/x86/kernel/cpu/bugs.c | 55 ++++++++++++++++++++++++++++++++++++++
1 file changed, 55 insertions(+)
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d48b0a941b2d..2323bfbcd694 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -300,6 +300,61 @@ static void x86_amd_ssb_disable(void)
#undef pr_fmt
#define pr_fmt(fmt) "MDS: " fmt
+/*
+ * Returns true if vulnerability should be mitigated based on the
+ * selected attack vector controls.
+ *
+ * See Documentation/admin-guide/hw-vuln/attack_vector_controls.rst
+ */
+static bool __init should_mitigate_vuln(unsigned int bug)
+{
+ switch (bug) {
+ /*
+ * The only runtime-selected spectre_v1 mitigations in the kernel are
+ * related to SWAPGS protection on kernel entry. Therefore, protection
+ * is only required for the user->kernel attack vector.
+ */
+ case X86_BUG_SPECTRE_V1:
+ return cpu_mitigate_attack_vector(CPU_MITIGATE_USER_KERNEL);
+
+ case X86_BUG_SPECTRE_V2:
+ case X86_BUG_RETBLEED:
+ case X86_BUG_SRSO:
+ case X86_BUG_L1TF:
+ return cpu_mitigate_attack_vector(CPU_MITIGATE_USER_KERNEL) ||
+ cpu_mitigate_attack_vector(CPU_MITIGATE_GUEST_HOST);
+
+ case X86_BUG_SPECTRE_V2_USER:
+ return cpu_mitigate_attack_vector(CPU_MITIGATE_USER_USER) ||
+ cpu_mitigate_attack_vector(CPU_MITIGATE_GUEST_GUEST);
+
+ /*
+ * All the vulnerabilities below allow potentially leaking data
+ * across address spaces. Therefore, mitigation is required for
+ * any of these 4 attack vectors.
+ */
+ case X86_BUG_MDS:
+ case X86_BUG_TAA:
+ case X86_BUG_MMIO_STALE_DATA:
+ case X86_BUG_RFDS:
+ case X86_BUG_SRBDS:
+ return cpu_mitigate_attack_vector(CPU_MITIGATE_USER_KERNEL) ||
+ cpu_mitigate_attack_vector(CPU_MITIGATE_GUEST_HOST) ||
+ cpu_mitigate_attack_vector(CPU_MITIGATE_USER_USER) ||
+ cpu_mitigate_attack_vector(CPU_MITIGATE_GUEST_GUEST);
+
+ case X86_BUG_GDS:
+ return cpu_mitigate_attack_vector(CPU_MITIGATE_USER_KERNEL) ||
+ cpu_mitigate_attack_vector(CPU_MITIGATE_GUEST_HOST) ||
+ cpu_mitigate_attack_vector(CPU_MITIGATE_USER_USER) ||
+ cpu_mitigate_attack_vector(CPU_MITIGATE_GUEST_GUEST) ||
+ (smt_mitigations != SMT_MITIGATIONS_OFF);
+ default:
+ WARN(1, "Unknown bug %x\n", bug);
+ return false;
+ }
+}
+
/* Default mitigation for MDS-affected CPUs */
static enum mds_mitigations mds_mitigation __ro_after_init =
IS_ENABLED(CONFIG_MITIGATION_MDS) ? MDS_MITIGATION_AUTO : MDS_MITIGATION_OFF;
--
2.34.1
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