linux-kernel - Re: [PATCH v6 5/5] x86/sev: Add SNP-specific unaccepted memory support

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Message-ID: <20221208221248.slltzm5ehnbltdee@box.shutemov.name>
Date:   Fri, 9 Dec 2022 01:12:48 +0300
From:   "Kirill A. Shutemov" <kirill@...temov.name>
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>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "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 v6 5/5] x86/sev: Add SNP-specific unaccepted memory
 support

On Thu, Dec 08, 2022 at 09:29:13AM -0600, 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.
> 
> Since the boot path and the core kernel paths perform similar operations,
> move the pvalidate_pages() and vmgexit_psc() functions into sev-shared.c
> to avoid code duplication.
> 
> 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  |  54 ++++++++++++++-
>  arch/x86/boot/compressed/sev.h  |  23 +++++++
>  arch/x86/include/asm/sev.h      |   3 +
>  arch/x86/kernel/sev-shared.c    | 103 +++++++++++++++++++++++++++++
>  arch/x86/kernel/sev.c           | 112 ++++----------------------------
>  arch/x86/mm/unaccepted_memory.c |   4 ++
>  8 files changed, 204 insertions(+), 99 deletions(-)
>  create mode 100644 arch/x86/boot/compressed/sev.h
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index d88f61940aa7..0704d4795919 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -1549,6 +1549,7 @@ config AMD_MEM_ENCRYPT
>  	select INSTRUCTION_DECODER
>  	select ARCH_HAS_CC_PLATFORM
>  	select X86_MEM_ENCRYPT
> +	select UNACCEPTED_MEMORY
>  	help
>  	  Say yes to enable support for the encryption of system memory.
>  	  This requires an AMD processor that supports Secure Memory

I think it misses "depends on EFI_STUB".

The code I've submitted contains "select EFI_STUB", but it causes build
issues for some configurations. I've changed it to "depends on" in git.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov