linux-kernel - Re: [PATCH v3 3/8] x86/sev: Require the RMPREAD instruction after Fam19h

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Message-ID: <20241018130618.GBZxJdSmQXOOgBRDLK@fat_crate.local>
Date: Fri, 18 Oct 2024 15:06:18 +0200
From: Borislav Petkov <bp@...en8.de>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: Dave Hansen <dave.hansen@...el.com>, linux-kernel@...r.kernel.org,
	x86@...nel.org, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Michael Roth <michael.roth@....com>,
	Ashish Kalra <ashish.kalra@....com>
Subject: Re: [PATCH v3 3/8] x86/sev: Require the RMPREAD instruction after
 Fam19h

On Mon, Sep 30, 2024 at 01:59:54PM -0500, Tom Lendacky wrote:
> The one issue we run into is that family 0x19 contains both Milan (zen3)
> and Genoa (zen4), so I'm not sure what to use as a good #define name. We
> have the same problem with family 0x17 which contains zen1 and zen2.
> 
> I might be able to change the if statement to something like:
> 
> 	if (!cpu_has(c, X86_FEATURE_HYPERVISOR) &&
> 	    (cpu_feature_enabled(X86_FEATURE_ZEN3) ||
> 	     cpu_feature_enabled(X86_FEATURE_ZEN4) ||
> 	     cpu_feature_enabled(X86_FEATURE_RMPREAD)) &&
> 	    snp_probe_rmptable_info()) {
> 
> which might make the intent clearer.
> 
> But, yes, I get your point about making grepping much easier, along with
> code readability. Maybe Boris and I can put our heads together to figure
> something out.

Right, that's why I'm adding the synthetic feature flags - for things like
that.

I think it is very readable this way and if this check needs to be repeated,
we can carve it out into a separate helper or so...

Thx.

-- 
Regards/Gruss,
    Boris.

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