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Date:   Thu, 4 Nov 2021 14:58:49 +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,
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        "H. Peter Anvin" <hpa@zytor.com>, Ard Biesheuvel <ardb@kernel.org>,
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Subject: Re: [PATCH v6 14/42] x86/sev: Register GHCB memory when SEV-SNP is
 active
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References: <20211008180453.462291-1-brijesh.singh@amd.com>
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On Wed, Nov 03, 2021 at 03:10:16PM -0500, Brijesh Singh wrote:
> Looking at the secondary CPU bring up path it seems that we will not be
> getting #VC until the early_setup_idt() is called. I am thinking to add
> function to register the GHCB from the early_setup_idt()
> 
> early_setup_idt()
> {
>   ...
>   if (IS_ENABLED(CONFIG_MEM_ENCRYPT))
>     sev_snp_register_ghcb()
>   ...
> }
> 
> The above will cover the APs

That will cover the APs during early boot as that is being called from
asm.

> and for BSP case I can call the same function just after the final IDT
> is loaded

Why after and not before?

> cpu_init_exception_handling()
> {
>    ...
>    ...
>    /* Finally load the IDT */
>    load_current_idt();
> 
>    if (IS_ENABLED(CONFIG_MEM_ENCRYPT))
>      sev_snp_register_ghcb()
> 
> }

That is also called on the APs - not only the BSP. trap_init() calls it
from start_kernel() which is the BSP and cpu_init_secondary() calls it
too, which is ofc the APs.

I guess that should be ok since you're calling the same function from
both but WTH do I know...

-- 
Regards/Gruss,
    Boris.

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