linux-kernel - Re: [PATCH v4 6/7] x86/cpu: Support AMD Automatic IBRS

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Date:   Fri, 2 Dec 2022 08:31:58 -0800
From:   Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>
To:     Kim Phillips <kim.phillips@....com>
Cc:     x86@...nel.org, Babu Moger <Babu.Moger@....com>,
        Borislav Petkov <bp@...en8.de>, Borislav Petkov <bp@...e.de>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Jonathan Corbet <corbet@....net>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        David Woodhouse <dwmw@...zon.co.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Juergen Gross <jgross@...e.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tony Luck <tony.luck@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Alexey Kardashevskiy <aik@....com>, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 6/7] x86/cpu: Support AMD Automatic IBRS

On Wed, Nov 30, 2022 at 07:50:02PM -0600, Kim Phillips wrote:
>--- a/Documentation/admin-guide/kernel-parameters.txt
>+++ b/Documentation/admin-guide/kernel-parameters.txt
>@@ -5698,9 +5698,12 @@
> 			retpoline,generic - Retpolines
> 			retpoline,lfence  - LFENCE; indirect branch
> 			retpoline,amd     - alias for retpoline,lfence
>-			eibrs		  - enhanced IBRS
>-			eibrs,retpoline   - enhanced IBRS + Retpolines
>-			eibrs,lfence      - enhanced IBRS + LFENCE
>+			eibrs		  - Enhanced/Auto IBRS
>+			autoibrs	  - Enhanced/Auto IBRS
>+			eibrs,retpoline   - Enhanced/Auto IBRS + Retpolines
>+			autoibrs,retpoline- Enhanced/Auto IBRS + Retpolines
>+			eibrs,lfence      - Enhanced/Auto IBRS + LFENCE
>+			autoibrs,lfence   - Enhanced/Auto IBRS + LFENCE
> 			ibrs		  - use IBRS to protect kernel

Documentation/admin-guide/hw-vuln/spectre.rst also needs an update.

>--- a/arch/x86/kernel/cpu/common.c
>+++ b/arch/x86/kernel/cpu/common.c
>@@ -1226,7 +1226,7 @@ static const __initconst struct x86_cpu_id cpu_vuln_whitelist[] = {
> 	VULNWL_AMD(0x12,	NO_MELTDOWN | NO_SSB | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
>
> 	/* FAMILY_ANY must be last, otherwise 0x0f - 0x12 matches won't work */
>-	VULNWL_AMD(X86_FAMILY_ANY,	NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),
>+	VULNWL_AMD(X86_FAMILY_ANY,	NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO | NO_EIBRS_PBRSB),
> 	VULNWL_HYGON(X86_FAMILY_ANY,	NO_MELTDOWN | NO_L1TF | NO_MDS | NO_SWAPGS | NO_ITLB_MULTIHIT | NO_MMIO),

I don't know if Hygon is ever going to get Automatic IBRS, but it
doesn't hurt to add NO_EIBRS_PBRSB to Hygon as well.