Re: [PATCH v3 0/2] x86: enforce and cleanup RIP-relative accesses in early boot code

From: Jacob Xu <jacobhxu@google.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Kevin Loughlin <kevinloughlin@google.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	 Ingo Molnar <mingo@redhat.com>,
	Dave Hansen <dave.hansen@linux.intel.com>,
	x86@kernel.org,  Nick Desaulniers <ndesaulniers@google.com>,
	Justin Stitt <justinstitt@google.com>,
	 Tom Lendacky <thomas.lendacky@amd.com>,
	Pankaj Gupta <pankaj.gupta@amd.com>,
	 Hou Wenlong <houwenlong.hwl@antgroup.com>,
	Ard Biesheuvel <ardb@kernel.org>,
	 Dionna Glaze <dionnaglaze@google.com>,
	Brijesh Singh <brijesh.singh@amd.com>,
	 Michael Roth <michael.roth@amd.com>,
	 "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	linux-kernel@vger.kernel.org,  llvm@lists.linux.dev,
	linux-coco@lists.linux.dev,  Ashish Kalra <ashish.kalra@amd.com>,
	Andi Kleen <ak@linux.intel.com>,
	 Adam Dunlap <acdunlap@google.com>,
	Peter Gonda <pgonda@google.com>,
	 Sidharth Telang <sidtelang@google.com>
Subject: Re: [PATCH v3 0/2] x86: enforce and cleanup RIP-relative accesses in early boot code
Date: Wed, 31 Jan 2024 10:16:55 -0800	[thread overview]
Message-ID: <CAJ5mJ6j-Vw2P=QLK-J_J79S35UggvZPtm5sia74=enR1qq9X9A@mail.gmail.com> (raw)
In-Reply-To: <20240131140037.GDZbpShX2b0elXlqDA@fat_crate.local>

On Wed, Jan 31, 2024 at 6:01 AM Borislav Petkov <bp@alien8.de> wrote:
>
> On Tue, Jan 30, 2024 at 10:08:43PM +0000, Kevin Loughlin wrote:
> > Instead, this patchset continues the approach of fixing the immediate
> > problem of SEV-SNP boots crashing when built by clang, providing a
> > backport-friendly set of changes needed to successfully boot SEV-SNP
> > hosts and guests.
>
> What use cases are those exactly? How do I reproduce them here?
>

We're interested in fixing SEV-SNP guest boots which are currently
broken when using a guest kernel compiled with clang. It seems like
every other user of SEV/SNP linux kernel code uses GCC to compile the
kernel so they've avoided this issue.

> SNP is not upstream yet and the SEV* code has been out there for a while
> now without a single such report so this must be something new happening
> due to <raisins>...?

E.g. Google COS uses clang to compile the kernel and we've made do
with an internal fix for a while. We've unfortunately just been rather
slow to report upstream.

>
> Thx.
>
> --
> Regards/Gruss,
>     Boris.
>
> https://people.kernel.org/tglx/notes-about-netiquette