linux-kernel - RE: [PATCH Part2 v6 02/49] iommu/amd: Introduce function to check SEV-SNP support

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Message-ID: <SN6PR12MB27678E2944605E11B37267CC8E759@SN6PR12MB2767.namprd12.prod.outlook.com>
Date:   Fri, 26 Aug 2022 18:54:16 +0000
From:   "Kalra, Ashish" <Ashish.Kalra@....com>
To:     Jarkko Sakkinen <jarkko@...nel.org>,
        Peter Gonda <pgonda@...gle.com>
CC:     the arch/x86 maintainers <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        kvm list <kvm@...r.kernel.org>,
        "linux-coco@...ts.linux.dev" <linux-coco@...ts.linux.dev>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Linux Crypto Mailing List <linux-crypto@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        "Lendacky, Thomas" <Thomas.Lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Sergio Lopez <slp@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Dov Murik <dovmurik@...ux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@....com>,
        Borislav Petkov <bp@...en8.de>,
        "Roth, Michael" <Michael.Roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>, Marc Orr <marcorr@...gle.com>,
        Sathyanarayanan Kuppuswamy 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        Alper Gun <alpergun@...gle.com>,
        "Dr. David Alan Gilbert" <dgilbert@...hat.com>
Subject: RE: [PATCH Part2 v6 02/49] iommu/amd: Introduce function to check
 SEV-SNP support

[AMD Official Use Only - General]

Hello Jarkko,

>> 
>> It really should be, in order to have any practical use:
>> 
>> 	if (no_iommu) {
>> 		pr_err("SEV-SNP: IOMMU is disabled.\n");
>> 		return false;
>> 	}
>> 
>> 	if (iommu_default_passthrough()) {
>> 		pr_err("SEV-SNP: IOMMU is configured in passthrough mode.\n");
>> 		return false;
>> 	}
>> 
>> The comment is *completely* redundant, it absolutely does not serve 
>> any sane purpose. It just tells what the code already clearly stating.
>> 
>> The combo error message on the other hand leaves you to the question 
>> "which one was it", and for that reason combining the checks leaves 
>> you to a louse debugging experience.

>Also, are those really *errors*? That implies that there is something wrong.

>Since you can have a legit configuration, IMHO they should be either warn or info. What do you think?

>They are definitely not errors

Yes, they can be warn or info, but as I mentioned above this patch is now part of IOMMU + SNP series,
so these comments are now relevant for that.

Thanks,
Ashish