From: Jim Mattson <jmattson@google.com>
To: Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
Daniel Sneddon <daniel.sneddon@linux.intel.com>,
Kai Huang <kai.huang@intel.com>,
Sandipan Das <sandipan.das@amd.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Cc: Jim Mattson <jmattson@google.com>,
Venkatesh Srinivas <venkateshs@chromium.org>
Subject: [PATCH v2 1/2] x86/cpufeatures: Define X86_FEATURE_AMD_IBPB_RET
Date: Fri, 16 Aug 2024 11:25:21 -0700 [thread overview]
Message-ID: <20240816182533.2478415-1-jmattson@google.com> (raw)
AMD's initial implementation of IBPB did not clear the return address
predictor. Beginning with Zen4, AMD's IBPB *does* clear the return
address predictor. This behavior is enumerated by
CPUID.80000008H:EBX.IBPB_RET[bit 30].
Define X86_FEATURE_AMD_IBPB_RET for use in KVM_GET_SUPPORTED_CPUID,
when determining cross-vendor capabilities.
Suggested-by: Venkatesh Srinivas <venkateshs@chromium.org>
Signed-off-by: Jim Mattson <jmattson@google.com>
---
arch/x86/include/asm/cpufeatures.h | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
index dd4682857c12..e5bcb428dcf9 100644
--- a/arch/x86/include/asm/cpufeatures.h
+++ b/arch/x86/include/asm/cpufeatures.h
@@ -348,6 +348,7 @@
#define X86_FEATURE_CPPC (13*32+27) /* "cppc" Collaborative Processor Performance Control */
#define X86_FEATURE_AMD_PSFD (13*32+28) /* Predictive Store Forwarding Disable */
#define X86_FEATURE_BTC_NO (13*32+29) /* Not vulnerable to Branch Type Confusion */
+#define X86_FEATURE_AMD_IBPB_RET (13*32+30) /* IBPB clears return address predictor */
#define X86_FEATURE_BRS (13*32+31) /* "brs" Branch Sampling available */
/* Thermal and Power Management Leaf, CPUID level 0x00000006 (EAX), word 14 */
--
2.46.0.184.g6999bdac58-goog
next reply other threads:[~2024-08-16 18:26 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-08-16 18:25 Jim Mattson [this message]
2024-08-16 18:25 ` [PATCH v2 2/2] KVM: x86: AMD's IBPB is not equivalent to Intel's IBPB Jim Mattson
2024-08-22 19:17 ` Sean Christopherson
2024-08-23 16:47 ` Venkatesh Srinivas
2024-08-23 16:06 ` Tom Lendacky
2024-08-23 17:33 ` Jim Mattson
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