linux-kernel - Re: [PATCH v3 0/5] efi: Don't initalize SEV-SNP from the EFI stub

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Message-ID: <d00c9119-5e8b-2615-8e4b-2d25732ff71a@amd.com>
Date: Tue, 22 Apr 2025 10:51:47 -0500
From: Tom Lendacky <thomas.lendacky@....com>
To: Ard Biesheuvel <ardb+git@...gle.com>, linux-efi@...r.kernel.org
Cc: x86@...nel.org, linux-kernel@...r.kernel.org, mingo@...nel.org,
 Ard Biesheuvel <ardb@...nel.org>, Borislav Petkov <bp@...en8.de>,
 Dionna Amalie Glaze <dionnaglaze@...gle.com>,
 Kevin Loughlin <kevinloughlin@...gle.com>
Subject: Re: [PATCH v3 0/5] efi: Don't initalize SEV-SNP from the EFI stub

On 4/22/25 05:07, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@...nel.org>
> 

Hi Ard,

I'll try to get to reviewing and testing this series very soon. But one
thing I can see is that we never set the snp_vmpl level anymore in the
EFI stub and so PVALIDATE will fail when running under an SVSM.

But I don't think this series is completely at fault. This goes back to
fixing memory acceptance before sev_enable() was called and I missed the
SVSM situation. So I don't think we can completely remove all SNP
initialization and might have to do svsm_setup_ca() which has a pre-req
on setup_cpuid_table()...  sigh.

Thanks,
Tom

> Changes since v2: [1]
> - rebase onto tip/x86/boot
> - add patch to remove unused static inline fallback implementation of
>   sev_enable()
> 
> Changes since v1: [0]
> - address shortcomings pointed out by Tom, related to missing checks and
>   to discovery of the CC blob table from the EFI stub
> 
> [0] https://lore.kernel.org/all/20250414130417.1486395-2-ardb+git@google.com/T/#u
> [1] https://lore.kernel.org/all/20250416165743.4080995-6-ardb+git@google.com/T/#u
> 
> Cc: Tom Lendacky <thomas.lendacky@....com>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Dionna Amalie Glaze <dionnaglaze@...gle.com>
> Cc: Kevin Loughlin <kevinloughlin@...gle.com>
> 
> Ard Biesheuvel (5):
>   x86/boot: Drop unused sev_enable() fallback
>   x86/efistub: Obtain SEV CC blob address from the stub
>   x86/boot: Drop redundant RMPADJUST in SEV SVSM presence check
>   x86/sev: Unify SEV-SNP hypervisor feature check
>   x86/efistub: Don't bother enabling SEV in the EFI stub
> 
>  arch/x86/boot/compressed/misc.h         | 11 -------
>  arch/x86/boot/compressed/sev.c          | 33 +-------------------
>  arch/x86/boot/startup/sev-shared.c      | 33 +++++++++++++++-----
>  arch/x86/boot/startup/sme.c             |  2 ++
>  arch/x86/coco/sev/core.c                | 11 -------
>  arch/x86/include/asm/sev-internal.h     |  3 +-
>  arch/x86/include/asm/sev.h              |  4 +--
>  drivers/firmware/efi/libstub/x86-stub.c | 27 +++++++++-------
>  8 files changed, 48 insertions(+), 76 deletions(-)
> 
> 
> base-commit: ff4c0560ab020d34baf0aa6434f66333d25ae524