linux-kernel - Re: [PATCH v1 04/26] x86/sev: Add the host SEV-SNP initialization support

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Date: Fri, 5 Jan 2024 17:09:16 +0100
From: Borislav Petkov <bp@...en8.de>
To: Jeremi Piotrowski <jpiotrowski@...ux.microsoft.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,
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	ak@...ux.intel.com, tony.luck@...el.com,
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	pankaj.gupta@....com, liam.merwick@...cle.com, zhi.a.wang@...el.com,
	Brijesh Singh <brijesh.singh@....com>
Subject: Re: [PATCH v1 04/26] x86/sev: Add the host SEV-SNP initialization
 support

On Thu, Jan 04, 2024 at 12:05:27PM +0100, Jeremi Piotrowski wrote:
> Is there a really good reason to perform the snp_probe_smptable_info() check at this
> point (instead of in snp_rmptable_init). snp_rmptable_init will also clear the cap
> on failure, and bsp_init_amd() runs too early to allow for the kernel to allocate the
> rmptable itself. I pointed out in the previous review that kernel allocation of rmptable
> is necessary in SNP-host capable VMs in Azure.

What does that even mean?

That function is doing some calculations after reading two MSRs. What
can possibly go wrong?!

-- 
Regards/Gruss,
    Boris.

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