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

From: Kevin Loughlin <kevinloughlin@google.com>
To: Borislav Petkov <bp@alien8.de>
Cc: Jacob Xu <jacobhxu@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: Fri, 2 Feb 2024 16:22:02 -0800	[thread overview]
Message-ID: <CAGdbjmJgu4euOTEzns4-7pqUWo8n-gNJiAfARoZWxw8T252zJQ@mail.gmail.com> (raw)
In-Reply-To: <20240131182944.GJZbqRmBN_KDgK_nmB@fat_crate.local>

On Wed, Jan 31, 2024 at 10:30 AM Borislav Petkov <bp@alien8.de> wrote:
>
> On Wed, Jan 31, 2024 at 10:16:55AM -0800, Jacob Xu wrote:
> > 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.
>
> Lemme give that a try here.
>
> > E.g. Google COS uses clang to compile the kernel and we've made do
> > with an internal fix for a while.
>
> Which means that, theoretically, you could forward-port this internal
> fix until the issue is fixed for real, I'd say.

True. I just think it would be better to have an upstream fix for
clang builds of SEV-SNP guests; I believe the first such SEV-SNP code
was merged in 5.19 if I'm not mistaken.