linux-kernel - Re: [PATCH v1 11/26] x86/sev: Invalidate pages from the direct map when adding them to the RMP table

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Date: Wed, 17 Jan 2024 10:34:00 +0100
From: Borislav Petkov <bp@...en8.de>
To: Dave Hansen <dave.hansen@...el.com>
Cc: Michael Roth <michael.roth@....com>, x86@...nel.org,
	kvm@...r.kernel.org, linux-coco@...ts.linux.dev, linux-mm@...ck.org,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
	tglx@...utronix.de, mingo@...hat.com, jroedel@...e.de,
	thomas.lendacky@....com, hpa@...or.com, ardb@...nel.org,
	pbonzini@...hat.com, seanjc@...gle.com, vkuznets@...hat.com,
	jmattson@...gle.com, luto@...nel.org, dave.hansen@...ux.intel.com,
	slp@...hat.com, pgonda@...gle.com, peterz@...radead.org,
	srinivas.pandruvada@...ux.intel.com, rientjes@...gle.com,
	tobin@....com, vbabka@...e.cz, kirill@...temov.name,
	ak@...ux.intel.com, tony.luck@...el.com,
	sathyanarayanan.kuppuswamy@...ux.intel.com, alpergun@...gle.com,
	jarkko@...nel.org, ashish.kalra@....com, nikunj.dadhania@....com,
	pankaj.gupta@....com, liam.merwick@...cle.com
Subject: Re: [PATCH v1 11/26] x86/sev: Invalidate pages from the direct map
 when adding them to the RMP table

On Tue, Jan 16, 2024 at 08:21:09AM -0800, Dave Hansen wrote:
> The problem will be the first time someone sees a regression when their
> direct-map-fracturing kernel feature (secret pages, SNP host, etc...)
> collides with some workload that's sensitive to kernel TLB pressure.

Yeah, and that "workload" will be some microbenchmark crap which people
would pay too much attention to, without it having any relevance to
real-world scenarios. Completely hypothetically speaking, ofc.

:-)

-- 
Regards/Gruss,
    Boris.

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