linux-kernel - Re: [sos-linux-ext-patches] [RFC 05/14] x86/apic: Initialize APIC ID for Secure AVIC

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Message-ID: <20241110163453.GAZzDgrYY2oO7fKvxl@fat_crate.local>
Date: Sun, 10 Nov 2024 17:34:53 +0100
From: Borislav Petkov <bp@...en8.de>
To: Neeraj Upadhyay <Neeraj.Upadhyay@....com>
Cc: "Melody (Huibo) Wang" <huibo.wang@....com>,
	linux-kernel@...r.kernel.org, tglx@...utronix.de, mingo@...hat.com,
	dave.hansen@...ux.intel.com, Thomas.Lendacky@....com,
	nikunj@....com, Santosh.Shukla@....com, Vasant.Hegde@....com,
	Suravee.Suthikulpanit@....com, David.Kaplan@....com, x86@...nel.org,
	hpa@...or.com, peterz@...radead.org, seanjc@...gle.com,
	pbonzini@...hat.com, kvm@...r.kernel.org
Subject: Re: [sos-linux-ext-patches] [RFC 05/14] x86/apic: Initialize APIC ID
 for Secure AVIC

On Sun, Nov 10, 2024 at 08:52:03PM +0530, Neeraj Upadhyay wrote:
> If I get your point, unless a corrective action is possible without
> hard reboot of the guest, doing a snp_abort() on detecting mismatch works better
> here. That way, the issue can be caught early, and it does not disrupt the running
> applications on a limping guest (which happens for the case where we only emit
> a warning). So, thinking more, snp_abort() looks more apt here.

Well, sometimes you have no influence on the HV (public cloud, for example).

So WARN_ONCE was on the right track but the error message should be more
user-friendly:

	WARN_ONCE(hv_apic_id != apic_id, 
		  "APIC IDs mismatch: %d (HV: %d). IPI handling will suffer!",
		  apic_id, hv_apic_id);

-- 
Regards/Gruss,
    Boris.

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