linux-kernel - Re: [PATCH] x86/CPU/AMD: Perform function calls post ZEN feature check regardless

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Message-ID: <20250812220341.GJaJu6PUo4Kl3pTprp@fat_crate.local>
Date: Wed, 13 Aug 2025 00:03:41 +0200
From: Borislav Petkov <bp@...en8.de>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: 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>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] x86/CPU/AMD: Perform function calls post ZEN feature
 check regardless

On Tue, Aug 12, 2025 at 04:56:29PM -0500, Tom Lendacky wrote:
> ZEN3 and ZEN4 won't be set if we do that and since those families don't
> have RMPREAD support, SNP won't get enabled on ZEN3 or ZEN4, so we can't
> do that.

That's why I said partly.

> Hmmm... i guess? Not sure I 100% agree with that.

Look at it this way: you can't really run old kernels on new hardware without
doing at least *some* backporting. So might as well do the family extension
patch too.

Let's worry about this when it really happens. But for a decade at SUSE I've
never even once thought: oh, this new machine support won't need backports.
Because it does every time and this is business as usual.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette