linux-kernel - Re: [PATCH v7 05/22] x86/sev: Move GHCB page based HV communication out of startup code

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Message-ID: <CAMj1kXF-aD74+O_xf_f902wq2RdPpiXCEjJ9osbnEwAMoN_5Rw@mail.gmail.com>
Date: Sun, 31 Aug 2025 12:52:16 +0200
From: Ard Biesheuvel <ardb@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: Ard Biesheuvel <ardb+git@...gle.com>, linux-kernel@...r.kernel.org, 
	linux-efi@...r.kernel.org, x86@...nel.org, Ingo Molnar <mingo@...nel.org>, 
	Kevin Loughlin <kevinloughlin@...gle.com>, Tom Lendacky <thomas.lendacky@....com>, 
	Josh Poimboeuf <jpoimboe@...nel.org>, Peter Zijlstra <peterz@...radead.org>, 
	Nikunj A Dadhania <nikunj@....com>
Subject: Re: [PATCH v7 05/22] x86/sev: Move GHCB page based HV communication
 out of startup code

On Sun, 31 Aug 2025 at 12:50, Borislav Petkov <bp@...en8.de> wrote:
>
> On Thu, Aug 28, 2025 at 12:22:08PM +0200, Ard Biesheuvel wrote:
> > diff --git a/arch/x86/boot/startup/sev-shared.c b/arch/x86/boot/startup/sev-shared.c
> > index 83c222a4f1fa..24cbeaf7ff4f 100644
> > --- a/arch/x86/boot/startup/sev-shared.c
> > +++ b/arch/x86/boot/startup/sev-shared.c
> > @@ -13,12 +13,9 @@
> >
> >  #ifndef __BOOT_COMPRESSED
> >  #define error(v)                     pr_err(v)
> > -#define has_cpuflag(f)                       boot_cpu_has(f)
>
> In file included from arch/x86/boot/startup/sev-startup.c:106:
> arch/x86/boot/startup/sev-shared.c: In function ‘pvalidate_4k_page’:
> arch/x86/boot/startup/sev-shared.c:661:26: error: implicit declaration of function ‘has_cpuflag’ [-Wimplicit-function-declaration]
>   661 |         if (validate && !has_cpuflag(X86_FEATURE_COHERENCY_SFW_NO))
>       |                          ^~~~~~~~~~~
> make[3]: *** [scripts/Makefile.build:287: arch/x86/boot/startup/sev-startup.o] Error 1
> make[2]: *** [scripts/Makefile.build:556: arch/x86/boot/startup] Error 2
> make[2]: *** Waiting for unfinished jobs....
> make[1]: *** [/mnt/kernel/kernel/linux/Makefile:2011: .] Error 2
> make: *** [Makefile:248: __sub-make] Error 2
>
> We probably will have to use the CPUID MSR protocol thing here or so...
>

Huh I thought I had fixed that: we can just keep that has_cpuflag()
definition if there is a need for it.