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Message-ID: <7a078451-172c-40f3-c2c7-4472c5006532@intel.com>
Date:   Fri, 2 Dec 2022 09:40:29 -0800
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Subject: Re: [PATCH v4 6/7] x86/cpu: Support AMD Automatic IBRS
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To:     Kim Phillips <kim.phillips@amd.com>, x86@kernel.org
Cc:     Babu Moger <Babu.Moger@amd.com>, Borislav Petkov <bp@alien8.de>,
        Borislav Petkov <bp@suse.de>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ingo Molnar <mingo@redhat.com>,
        Joao Martins <joao.m.martins@oracle.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        David Woodhouse <dwmw@amazon.co.uk>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Juergen Gross <jgross@suse.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Tony Luck <tony.luck@intel.com>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        Alexey Kardashevskiy <aik@amd.com>, kvm@vger.kernel.org,
        linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org
References: <20221201015003.295769-1-kim.phillips@amd.com>
 <20221201015003.295769-7-kim.phillips@amd.com>
From:   Dave Hansen <dave.hansen@intel.com>
In-Reply-To: <20221201015003.295769-7-kim.phillips@amd.com>
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On 11/30/22 17:50, Kim Phillips wrote:
> @@ -1240,8 +1240,11 @@ static const struct {
>  	{ "retpoline,lfence",	SPECTRE_V2_CMD_RETPOLINE_LFENCE,  false },
>  	{ "retpoline,generic",	SPECTRE_V2_CMD_RETPOLINE_GENERIC, false },
>  	{ "eibrs",		SPECTRE_V2_CMD_EIBRS,		  false },
> +	{ "autoibrs",		SPECTRE_V2_CMD_EIBRS,		  false },
>  	{ "eibrs,lfence",	SPECTRE_V2_CMD_EIBRS_LFENCE,	  false },
> +	{ "autoibrs,lfence",	SPECTRE_V2_CMD_EIBRS_LFENCE,	  false },
>  	{ "eibrs,retpoline",	SPECTRE_V2_CMD_EIBRS_RETPOLINE,	  false },
> +	{ "autoibrs,retpoline",	SPECTRE_V2_CMD_EIBRS_RETPOLINE,	  false },
>  	{ "auto",		SPECTRE_V2_CMD_AUTO,		  false },
>  	{ "ibrs",		SPECTRE_V2_CMD_IBRS,              false },

I don't think we should expose "autoibrs" to end users like this.
"eibrs" means always-on IBRS.  Intel did it first, so gets to name it.
Those are the rules, and it's why we call it "x86_64" and not whatever
Intel's silly name for it was.

Also, expanding the strings:

> +	[SPECTRE_V2_EIBRS_RETPOLINE]		= "Mitigation: Enhanced / Automatic IBRS + Retpolines",

is fine, but adding new user-visible options that we have to document is
not.