linux-kernel - Re: [PATCH v2 05/12] x86/sev: Use GHCB protocol version 2 if supported

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Date:   Wed, 3 Nov 2021 17:05:04 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Joerg Roedel <joro@...tes.org>,
        Brijesh Singh <brijesh.singh@....com>
Cc:     x86@...nel.org, Eric Biederman <ebiederm@...ssion.com>,
        kexec@...ts.infradead.org, Joerg Roedel <jroedel@...e.de>,
        hpa@...or.com, Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Jiri Slaby <jslaby@...e.cz>,
        Dan Williams <dan.j.williams@...el.com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Cfir Cohen <cfir@...gle.com>,
        Erdem Aktas <erdemaktas@...gle.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mike Stunes <mstunes@...are.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Martin Radev <martin.b.radev@...il.com>,
        Arvind Sankar <nivedita@...m.mit.edu>,
        linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org,
        kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH v2 05/12] x86/sev: Use GHCB protocol version 2 if
 supported

On Mon, Sep 13, 2021 at 05:55:56PM +0200, Joerg Roedel wrote:
> From: Joerg Roedel <jroedel@...e.de>
> 
> Check whether the hypervisor supports GHCB version 2 and use it if
> available.
> 
> Signed-off-by: Joerg Roedel <jroedel@...e.de>
> ---
>  arch/x86/boot/compressed/sev.c | 10 ++++++++--
>  arch/x86/include/asm/sev.h     |  4 ++--
>  arch/x86/kernel/sev-shared.c   | 17 ++++++++++++++---
>  3 files changed, 24 insertions(+), 7 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
> index 101e08c67296..7f8416f76be7 100644
> --- a/arch/x86/boot/compressed/sev.c
> +++ b/arch/x86/boot/compressed/sev.c
> @@ -119,16 +119,22 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
>  /* Include code for early handlers */
>  #include "../../kernel/sev-shared.c"
>  
> +static unsigned int ghcb_protocol;

I guess you need to sync up with Brijesh on what to use:

https://lore.kernel.org/r/20211008180453.462291-7-brijesh.singh@amd.com

And if ghcb_version there is __ro_after_init I think that's perfectly
fine and doesn't need an accessor...

Thx.

-- 
Regards/Gruss,
    Boris.

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