linux-kernel - Re: [PATCH v3 2/2] x86/sev: Add SNP-specific unaccepted memory support

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Message-ID: <Yv5BKgbwNC2WY2/+@zn.tnic>
Date:   Thu, 18 Aug 2022 15:39:54 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        "H. Peter Anvin" <hpa@...or.com>,
        Michael Roth <michael.roth@....com>,
        Joerg Roedel <jroedel@...e.de>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3 2/2] x86/sev: Add SNP-specific unaccepted memory
 support

On Mon, Aug 15, 2022 at 10:57:43AM -0500, Tom Lendacky wrote:
> Add SNP-specific hooks to the unaccepted memory support in the boot
> path (__accept_memory()) and the core kernel (accept_memory()) in order
> to support booting SNP guests when unaccepted memory is present. Without
> this support, SNP guests will fail to boot and/or panic() when unaccepted
> memory is present in the EFI memory map.
> 
> The process of accepting memory under SNP involves invoking the hypervisor
> to perform a page state change for the page to private memory and then
> issuing a PVALIDATE instruction to accept the page.
> 
> Create the new header file arch/x86/boot/compressed/sev.h because adding
> the function declaration to any of the existing SEV related header files
> pulls in too many other header files, causing the build to fail.
> 
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> ---
>  arch/x86/Kconfig                |  1 +
>  arch/x86/boot/compressed/mem.c  |  3 +++
>  arch/x86/boot/compressed/sev.c  | 10 +++++++++-
>  arch/x86/boot/compressed/sev.h  | 23 +++++++++++++++++++++++
>  arch/x86/include/asm/sev.h      |  3 +++
>  arch/x86/kernel/sev.c           | 16 ++++++++++++++++
>  arch/x86/mm/unaccepted_memory.c |  4 ++++
>  7 files changed, 59 insertions(+), 1 deletion(-)
>  create mode 100644 arch/x86/boot/compressed/sev.h

Looks mostly ok to me...

> diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
> index 730c4677e9db..d4b06c862094 100644
> --- a/arch/x86/boot/compressed/sev.c
> +++ b/arch/x86/boot/compressed/sev.c
> @@ -115,7 +115,7 @@ static enum es_result vc_read_mem(struct es_em_ctxt *ctxt,
>  /* Include code for early handlers */
>  #include "../../kernel/sev-shared.c"
>  
> -static inline bool sev_snp_enabled(void)
> +bool sev_snp_enabled(void)
>  {
>  	return sev_status & MSR_AMD64_SEV_SNP_ENABLED;
>  }

This is another one of my pet peeves and now it even gets exported but
it is the early decompressor crap so I won't even try to mention cc_*
helpers...

-- 
Regards/Gruss,
    Boris.

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