linux-kernel - [PATCH v4 12/19] x86/virt: Drop unnecessary check on extended CPUID level in cpu_has

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:   Fri, 21 Jul 2023 13:18:52 -0700
From:   Sean Christopherson <seanjc@...gle.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Andrew Cooper <Andrew.Cooper3@...rix.com>,
        Kai Huang <kai.huang@...el.com>, Chao Gao <chao.gao@...el.com>
Subject: [PATCH v4 12/19] x86/virt: Drop unnecessary check on extended CPUID
 level in cpu_has_svm()

Drop the explicit check on the extended CPUID level in cpu_has_svm(), the
kernel's cached CPUID info will leave the entire SVM leaf unset if said
leaf is not supported by hardware.  Prior to using cached information,
the check was needed to avoid false positives due to Intel's rather crazy
CPUID behavior of returning the values of the maximum supported leaf if
the specified leaf is unsupported.

Fixes: 682a8108872f ("x86/kvm/svm: Simplify cpu_has_svm()")
Signed-off-by: Sean Christopherson <seanjc@...gle.com>
---
 arch/x86/include/asm/virtext.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/arch/x86/include/asm/virtext.h b/arch/x86/include/asm/virtext.h
index a27801f2bc71..be50c414efe4 100644
--- a/arch/x86/include/asm/virtext.h
+++ b/arch/x86/include/asm/virtext.h
@@ -39,12 +39,6 @@ static inline int cpu_has_svm(const char **msg)
 		return 0;
 	}
 
-	if (boot_cpu_data.extended_cpuid_level < SVM_CPUID_FUNC) {
-		if (msg)
-			*msg = "can't execute cpuid_8000000a";
-		return 0;
-	}
-
 	if (!boot_cpu_has(X86_FEATURE_SVM)) {
 		if (msg)
 			*msg = "svm not available";
-- 
2.41.0.487.g6d72f3e995-goog