Date:   Wed, 22 Dec 2021 14:16:40 +0100
From:   Borislav Petkov <bp@alien8.de>
To:     Brijesh Singh <brijesh.singh@amd.com>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
        linux-efi@vger.kernel.org, platform-driver-x86@vger.kernel.org,
        linux-coco@lists.linux.dev, linux-mm@kvack.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Joerg Roedel <jroedel@suse.de>,
        Tom Lendacky <thomas.lendacky@amd.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Ard Biesheuvel <ardb@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <seanjc@google.com>,
        Vitaly Kuznetsov <vkuznets@redhat.com>,
        Jim Mattson <jmattson@google.com>,
        Andy Lutomirski <luto@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Sergio Lopez <slp@redhat.com>, Peter Gonda <pgonda@google.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
        David Rientjes <rientjes@google.com>,
        Dov Murik <dovmurik@linux.ibm.com>,
        Tobin Feldman-Fitzthum <tobin@ibm.com>,
        Michael Roth <michael.roth@amd.com>,
        Vlastimil Babka <vbabka@suse.cz>,
        "Kirill A . Shutemov" <kirill@shutemov.name>,
        Andi Kleen <ak@linux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@redhat.com>,
        tony.luck@intel.com, marcorr@google.com,
        sathyanarayanan.kuppuswamy@linux.intel.com
Subject: Re: [PATCH v8 11/40] x86/sev: Register GHCB memory when SEV-SNP is
 active
Message-ID: <YcMlOOPp2rTFKkeW@zn.tnic>
References: <20211210154332.11526-1-brijesh.singh@amd.com>
 <20211210154332.11526-12-brijesh.singh@amd.com>
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On Fri, Dec 10, 2021 at 09:43:03AM -0600, Brijesh Singh wrote:
> @@ -652,7 +652,7 @@ static enum es_result vc_handle_msr(struct ghcb *ghcb, struct es_em_ctxt *ctxt)
>   * This function runs on the first #VC exception after the kernel
>   * switched to virtual addresses.
>   */
> -static bool __init sev_es_setup_ghcb(void)
> +static bool __init setup_ghcb(void)
>  {
>  	/* First make sure the hypervisor talks a supported protocol. */
>  	if (!sev_es_negotiate_protocol())

Ok, let me stare at this for a while:

This gets called by handle_vc_boot_ghcb() which gets set at build time:

arch/x86/kernel/head_64.S:372:SYM_DATA(initial_vc_handler,      .quad handle_vc_boot_ghcb)

initial_vc_handler() gets called by vc_boot_ghcb() which gets set in

early_setup_idt()

and that function already does sev_snp_register_ghcb().

So why don't you concentrate the work setup_ghcb() does before the first
#VC and call it in early_setup_idt(), before the IDT is set?

And then you get rid of yet another setup-at-first-use case?

Thx.

-- 
Regards/Gruss,
    Boris.

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