linux-kernel - Re: [PATCH Part2 v5 05/45] x86/sev: Add helper functions for RMPUPDATE and PSMASH instruction

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Message-ID: <YWnkMXdL89AHPF10@google.com>
Date:   Fri, 15 Oct 2021 20:27:29 +0000
From:   Sean Christopherson <seanjc@...gle.com>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.org,
        linux-crypto@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Joerg Roedel <jroedel@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.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 Gonda <pgonda@...gle.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>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>, tony.luck@...el.com,
        marcorr@...gle.com, sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH Part2 v5 05/45] x86/sev: Add helper functions for
 RMPUPDATE and PSMASH instruction

On Fri, Oct 15, 2021, Brijesh Singh wrote:
> On 10/15/21 1:05 PM, Sean Christopherson wrote:
> > On Fri, Aug 20, 2021, Brijesh Singh wrote:
> >> +	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
> > Shouldn't this be a WARN_ON_ONCE()?
> 
> Since some of these function are called while handling the PSC so I
> tried to avoid using the WARN -- mainly because if the warn_on_panic=1
> is set on the host then it will result in the kernel panic.

But why would KVM be handling PSC requests if SNP is disabled?