From: Kiryl Shutsemau <kas@kernel.org>
To: Zack Rusin <zack.rusin@broadcom.com>
Cc: Borislav Petkov <bp@alien8.de>,
Ajay Kaher <ajay.kaher@broadcom.com>,
Alexey Makhalov <alexey.makhalov@broadcom.com>,
x86@kernel.org, Dennis Zhou <dennis@kernel.org>,
Tejun Heo <tj@kernel.org>, Arnd Bergmann <arnd@arndb.de>,
Rick Edgecombe <rick.p.edgecombe@intel.com>,
Thomas Gleixner <tglx@kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H . Peter Anvin" <hpa@zytor.com>,
virtualization@lists.linux.dev,
bcm-kernel-feedback-list@broadcom.com,
linux-kernel@vger.kernel.org, Christoph Lameter <cl@gentwo.org>,
Andrew Morton <akpm@linux-foundation.org>,
Tom Lendacky <thomas.lendacky@amd.com>,
Bo Gan <bo.gan@broadcom.com>,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-coco@lists.linux.dev, kvm@vger.kernel.org
Subject: Re: [PATCH v1 1/2] percpu: Use X86_MEM_ENCRYPT for decrypted per-CPU data
Date: Wed, 16 Sep 2026 12:14:28 +0100 [thread overview]
Message-ID: <aqp5yxa2qcsv-dvt@thinkstation> (raw)
In-Reply-To: <07cdda86e2c60b27a18023e2e5fae339b78db0ab.1789488039.git.zack.rusin@broadcom.com>
On Wed, Sep 16, 2026 at 01:05:39AM -0400, Zack Rusin wrote:
> Decrypted per-CPU data is gated by AMD_MEM_ENCRYPT. With
> INTEL_TDX_GUEST=y and AMD_MEM_ENCRYPT=n it falls back to ordinary
> per-CPU storage, so converting a variable to shared memory can expose
> unrelated data on the same page.
>
> Gate the declarations and linker section on X86_MEM_ENCRYPT, which both
> AMD_MEM_ENCRYPT and INTEL_TDX_GUEST select. Existing AMD configurations
> are unchanged.
>
> Keep the decrypted subsection page-aligned at both ends. The per-CPU
> template and each allocated per-CPU unit are also page-aligned, so page
> conversion cannot expose ordinary per-CPU data. TDX-only configurations
> may need additional space for this alignment and isolation.
>
> Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
> ---
> include/asm-generic/vmlinux.lds.h | 2 +-
> include/linux/percpu-defs.h | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index b2988aa12f66..1448e791773e 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -1013,7 +1013,7 @@
> * Note: We use a separate section so that only this section gets
> * decrypted to avoid exposing more than we wish.
> */
> -#ifdef CONFIG_AMD_MEM_ENCRYPT
> +#ifdef CONFIG_X86_MEM_ENCRYPT
> #define PERCPU_DECRYPTED_SECTION \
> . = ALIGN(PAGE_SIZE); \
> *(.data..percpu..decrypted) \
> diff --git a/include/linux/percpu-defs.h b/include/linux/percpu-defs.h
> index dbe3267a0a13..54ce1442d918 100644
> --- a/include/linux/percpu-defs.h
> +++ b/include/linux/percpu-defs.h
> @@ -172,7 +172,7 @@
> * Declaration/definition used for per-CPU variables that should be accessed
> * as decrypted when memory encryption is enabled in the guest.
> */
> -#ifdef CONFIG_AMD_MEM_ENCRYPT
> +#ifdef CONFIG_X86_MEM_ENCRYPT
> #define DECLARE_PER_CPU_DECRYPTED(type, name) \
> DECLARE_PER_CPU_SECTION(type, name, "..decrypted")
DECLARE_PER_CPU_DECRYPTED() is not used anywhere. Do we want to drop it?
Otherwise:
Acked-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
--
Kiryl Shutsemau / Kirill A. Shutemov
next prev parent reply other threads:[~2026-09-16 11:14 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-16 5:05 [PATCH v1 0/2] x86/vmware: Share steal-time storage in encrypted guests Zack Rusin
2026-09-16 5:05 ` [PATCH v1 1/2] percpu: Use X86_MEM_ENCRYPT for decrypted per-CPU data Zack Rusin
2026-09-16 11:14 ` Kiryl Shutsemau [this message]
2026-09-16 5:05 ` [PATCH v1 2/2] x86/vmware: Decrypt steal-time storage before sharing it Zack Rusin
2026-09-16 12:18 ` [PATCH v1 0/2] x86/vmware: Share steal-time storage in encrypted guests Kiryl Shutsemau
2026-09-16 15:41 ` Zack Rusin
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