linux-kernel - Re: [PATCH v2 08/12] x86/sev: Park APs on AP Jump Table with GHCB protocol version 2

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Message-ID: <YfJfa955Pkg1y6Gv@suse.de>
Date:   Thu, 27 Jan 2022 10:01:31 +0100
From:   Joerg Roedel <jroedel@...e.de>
To:     Borislav Petkov <bp@...en8.de>
Cc:     Joerg Roedel <joro@...tes.org>, x86@...nel.org,
        Eric Biederman <ebiederm@...ssion.com>,
        kexec@...ts.infradead.org, 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 08/12] x86/sev: Park APs on AP Jump Table with GHCB
 protocol version 2

On Fri, Nov 12, 2021 at 05:33:05PM +0100, Borislav Petkov wrote:
> On Mon, Sep 13, 2021 at 05:55:59PM +0200, Joerg Roedel wrote:
> > +		     "ljmpl	*%0" : :
> > +		     "m" (real_mode_header->sev_real_ap_park_asm),
> > +		     "b" (sev_es_jump_table_pa >> 4));
> 
> In any case, this asm needs comments: why those regs, why
> sev_es_jump_table_pa >> 4 in rbx (I found later in the patch why) and so
> on.

Turned out the jump_table_pa is not used in asm code anymore. It was a
left-over from a previous version of the patch, it is removed now.

> > +SYM_INNER_LABEL(sev_ap_park_paging_off, SYM_L_GLOBAL)
> 
> Global symbol but used only in this file. .L-prefix then?

It needs to be a global symbol so the pa_ variant can be generated.

Regards,

-- 
Jörg Rödel
jroedel@...e.de

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