linux-kernel - Re: [PATCH v5 02/22] x86/sev: Use MSR protocol for remapping SVSM calling area

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Message-ID: <CAMj1kXEeinL-2yZTVqDAz3iStpOTVrbb98Xk2p=P6V+TZ9wH9g@mail.gmail.com>
Date: Fri, 18 Jul 2025 19:45:56 +1000
From: Ard Biesheuvel <ardb@...nel.org>
To: Tom Lendacky <thomas.lendacky@....com>
Cc: Ard Biesheuvel <ardb+git@...gle.com>, linux-kernel@...r.kernel.org, 
	linux-efi@...r.kernel.org, x86@...nel.org, Borislav Petkov <bp@...en8.de>, 
	Ingo Molnar <mingo@...nel.org>, Kevin Loughlin <kevinloughlin@...gle.com>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Nikunj A Dadhania <nikunj@....com>
Subject: Re: [PATCH v5 02/22] x86/sev: Use MSR protocol for remapping SVSM
 calling area

On Thu, 17 Jul 2025 at 03:03, Tom Lendacky <thomas.lendacky@....com> wrote:
>
> On 7/15/25 22:18, Ard Biesheuvel wrote:
> > From: Ard Biesheuvel <ardb@...nel.org>
> >
> > As the preceding code comment already indicates, remapping the SVSM
> > calling area occurs long before the GHCB page is configured, and so
> > calling svsm_perform_call_protocol() is guaranteed to result in a call
> > to svsm_perform_msr_protocol().
> >
> > So just call the latter directly. This allows most of the GHCB based API
> > infrastructure to be moved out of the startup code in a subsequent
> > patch.
> >
> > Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> > Reviewed-by: Borislav Petkov (AMD) <bp@...en8.de>
> > Reviewed-by: Tom Lendacky <thomas.lendacky@....com>
> > ---
> >  arch/x86/boot/startup/sev-shared.c  | 11 +++++++++++
> >  arch/x86/boot/startup/sev-startup.c |  5 ++---
> >  2 files changed, 13 insertions(+), 3 deletions(-)
> >
> > diff --git a/arch/x86/boot/startup/sev-shared.c b/arch/x86/boot/startup/sev-shared.c
> > index c401d0391537..60ab09b3149d 100644
> > --- a/arch/x86/boot/startup/sev-shared.c
> > +++ b/arch/x86/boot/startup/sev-shared.c
> > @@ -723,6 +723,17 @@ static void __head setup_cpuid_table(const struct cc_blob_sev_info *cc_info)
> >       }
> >  }
> >
> > +static int __head svsm_call_msr_protocol(struct svsm_call *call)
> > +{
> > +     int ret;
> > +
> > +     do {
> > +             ret = svsm_perform_msr_protocol(call);
> > +     } while (ret == -EAGAIN);
> > +
> > +     return ret;
> > +}
> > +
> >  static void __head svsm_pval_4k_page(unsigned long paddr, bool validate)
> >  {
> >       struct svsm_pvalidate_call *pc;
> > diff --git a/arch/x86/boot/startup/sev-startup.c b/arch/x86/boot/startup/sev-startup.c
> > index 0b7e3b950183..c30e0eed0131 100644
> > --- a/arch/x86/boot/startup/sev-startup.c
> > +++ b/arch/x86/boot/startup/sev-startup.c
> > @@ -295,7 +295,6 @@ static __head struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
> >  static __head void svsm_setup(struct cc_blob_sev_info *cc_info)
> >  {
> >       struct svsm_call call = {};
> > -     int ret;
> >       u64 pa;
> >
> >       /*
> > @@ -325,8 +324,8 @@ static __head void svsm_setup(struct cc_blob_sev_info *cc_info)
> >       call.caa = svsm_get_caa();
> >       call.rax = SVSM_CORE_CALL(SVSM_CORE_REMAP_CA);
> >       call.rcx = pa;
> > -     ret = svsm_perform_call_protocol(&call);
> > -     if (ret)
> > +
> > +     if (svsm_perform_msr_protocol(&call))
>
> This should be svsm_call_msr_protocol().
>

OK will fix