linux-kernel - [PATCH] x86/CPU/AMD: Perform function calls post ZEN feature check regardless

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Message-ID: <ee4e9ea71713cee72bb637e848c6a272f8a9e631.1753290066.git.thomas.lendacky@amd.com>
Date: Wed, 23 Jul 2025 12:01:06 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: <linux-kernel@...r.kernel.org>, <x86@...nel.org>
CC: Borislav Petkov <bp@...en8.de>, Thomas Gleixner <tglx@...utronix.de>, Ingo
 Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>, "H.
 Peter Anvin" <hpa@...or.com>
Subject: [PATCH] x86/CPU/AMD: Perform function calls post ZEN feature check regardless

Currently, if a ZEN family/model is not recognized in bsp_init_amd(), then
function calls after the family/model check are skipped. This can prevent
older kernels from enabling features on newer hardware, e.g., unrecognized
new hardware won't enable SEV-SNP because bsp_determine_snp() is skipped.

Rearrange the way the WARN_ONCE() is issued so that functions called after
the family/model check are still called.

Fixes: 216d106c7ff7 ("x86/sev: Add SEV-SNP host initialization support")
Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
---
 arch/x86/kernel/cpu/amd.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
index a5ece6ebe8a7..79ea6a0fcf8a 100644
--- a/arch/x86/kernel/cpu/amd.c
+++ b/arch/x86/kernel/cpu/amd.c
@@ -420,6 +420,8 @@ static void tsa_init(struct cpuinfo_x86 *c)

 static void bsp_init_amd(struct cpuinfo_x86 *c)
 {
+	bool model_warn = false;
+
 	if (cpu_has(c, X86_FEATURE_CONSTANT_TSC)) {

 		if (c->x86 > 0x10 ||
@@ -489,7 +491,7 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
 			setup_force_cpu_cap(X86_FEATURE_ZEN2);
 			break;
 		default:
-			goto warn;
+			model_warn = true;
 		}
 		break;

@@ -504,7 +506,7 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
 			setup_force_cpu_cap(X86_FEATURE_ZEN4);
 			break;
 		default:
-			goto warn;
+			model_warn = true;
 		}
 		break;

@@ -521,7 +523,7 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
 			setup_force_cpu_cap(X86_FEATURE_ZEN6);
 			break;
 		default:
-			goto warn;
+			model_warn = true;
 		}
 		break;

@@ -529,16 +531,13 @@ static void bsp_init_amd(struct cpuinfo_x86 *c)
 		break;
 	}

+	WARN_ONCE(model_warn, "Family 0x%x, model: 0x%x??\n", c->x86, c->x86_model);
+
 	bsp_determine_snp(c);
 	tsa_init(c);

 	if (cpu_has(c, X86_FEATURE_GP_ON_USER_CPUID))
 		setup_force_cpu_cap(X86_FEATURE_CPUID_FAULT);
-
-	return;
-
-warn:
-	WARN_ONCE(1, "Family 0x%x, model: 0x%x??\n", c->x86, c->x86_model);
 }

 static void early_detect_mem_encrypt(struct cpuinfo_x86 *c)

base-commit: 804fa10c3a3c8a33ce6ffdb999f94d3a7a6c20b8
-- 
2.46.2