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List:       linux-doc
Subject:    Re: [PATCH v3 6/7] x86/cpu, kvm: Support AMD Automatic IBRS
From:       Pawan Gupta <pawan.kumar.gupta () linux ! intel ! com>
Date:       2022-11-30 20:36:49
Message-ID: 20221130203649.gwhypmw35mfgwsxh () desk
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On Tue, Nov 29, 2022 at 05:58:15PM -0600, Kim Phillips wrote:
>--- a/arch/x86/kernel/cpu/common.c
>+++ b/arch/x86/kernel/cpu/common.c
>@@ -1406,6 +1406,14 @@ static void __init cpu_set_bug_bits(struct cpuinfo_x86 *c)
> 	    !(ia32_cap & ARCH_CAP_PBRSB_NO))
> 		setup_force_cpu_bug(X86_BUG_EIBRS_PBRSB);
>
>+	/*
>+	 * AMD's AutoIBRS is equivalent to Intel's eIBRS - use the Intel flag only
>+	 * after IBRS_ENHANCED bugs such as BUG_EIBRS_PBRSB above have been
>+	 * determined.
>+	 */

Minor comment, setting NO_EIBRS_PBRSB in cpu_vuln_whitelist for
non-EIBRS CPUs also (AMD and others) can remove this order dependency.

>+	if (cpu_has(c, X86_FEATURE_AUTOIBRS))
>+		setup_force_cpu_cap(X86_FEATURE_IBRS_ENHANCED);
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