linux-kernel - Re: [PATCH v9 15/43] x86/sev: Register GHCB memory when SEV-SNP is active

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Date:   Wed, 2 Feb 2022 11:34:48 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        linux-efi@...r.kernel.org, platform-driver-x86@...r.kernel.org,
        linux-coco@...ts.linux.dev, linux-mm@...ck.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>,
        Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.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>,
        Michael Roth <michael.roth@....com>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill@...temov.name>,
        Andi Kleen <ak@...ux.intel.com>,
        "Dr . David Alan Gilbert" <dgilbert@...hat.com>,
        brijesh.ksingh@...il.com, tony.luck@...el.com, marcorr@...gle.com,
        sathyanarayanan.kuppuswamy@...ux.intel.com
Subject: Re: [PATCH v9 15/43] x86/sev: Register GHCB memory when SEV-SNP is
 active

On Fri, Jan 28, 2022 at 11:17:36AM -0600, Brijesh Singh wrote:
> diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> index 24df739c9c05..b86b48b66a44 100644
> --- a/arch/x86/kernel/sev.c
> +++ b/arch/x86/kernel/sev.c
> @@ -41,7 +41,7 @@ static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE);
>   * Needs to be in the .data section because we need it NULL before bss is
>   * cleared
>   */
> -static struct ghcb __initdata *boot_ghcb;
> +static struct ghcb *boot_ghcb __section(".data");
>  
>  /* Bitmap of SEV features supported by the hypervisor */
>  static u64 sev_hv_features __ro_after_init;
> @@ -161,55 +161,6 @@ void noinstr __sev_es_ist_exit(void)
>  	this_cpu_write(cpu_tss_rw.x86_tss.ist[IST_INDEX_VC], *(unsigned long *)ist);
>  }
>  
> -/*
> - * Nothing shall interrupt this code path while holding the per-CPU
> - * GHCB. The backup GHCB is only for NMIs interrupting this path.
> - *
> - * Callers must disable local interrupts around it.
> - */
> -static noinstr struct ghcb *__sev_get_ghcb(struct ghcb_state *state)

That move doesn't look like it's needed anymore, does it?

I mean, it builds even without it.

-- 
Regards/Gruss,
    Boris.

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