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Wed, 16 Sep 2026 07:14:29 -0400 (EDT) Date: Wed, 16 Sep 2026 12:14:28 +0100 From: Kiryl Shutsemau To: Zack Rusin Cc: Borislav Petkov , Ajay Kaher , Alexey Makhalov , x86@kernel.org, Dennis Zhou , Tejun Heo , Arnd Bergmann , Rick Edgecombe , Thomas Gleixner , Ingo Molnar , Dave Hansen , "H . Peter Anvin" , virtualization@lists.linux.dev, bcm-kernel-feedback-list@broadcom.com, linux-kernel@vger.kernel.org, Christoph Lameter , Andrew Morton , Tom Lendacky , Bo Gan , 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 Message-ID: References: <07cdda86e2c60b27a18023e2e5fae339b78db0ab.1789488039.git.zack.rusin@broadcom.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <07cdda86e2c60b27a18023e2e5fae339b78db0ab.1789488039.git.zack.rusin@broadcom.com> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 372D210000C X-Stat-Signature: ecj7k4rrae5ymwwbip9j5b1payiyn5jw X-HE-Tag: 1789557278-510229 X-HE-Meta: U2FsdGVkX19lCJsgskY9mZgJu1Kh5X/V+8woFEt3KhTfMo++H14BC6YeEiyNMM4brJQy6y8qgGtD2W6aKpiYMPLNtfLlOSOQeOcqGDXlGnK6zh+dw5sI7mCmGXdEBMewX9vWs3sD2btWr7rPtTNx3jEYDX17Kh7Rtw8NkV+Itb1KisLQsJ7HqE/Yv892JIVGAbJs57SbmtnlN7/syUrXhlzcHhEICYPSbR9ccazLhUaVCQlMU9p8htfcQ6qIAsBfXq+OoqUu2p0SZAka6c6b2Jvr7HtLkoudu6ED9OQl/31jriWUYYv72qNxneEnocPFVhH78nLfXnX4v9mvKMfhlUVUOwwtsPT774dKk/CUd/H0z/mab1uxVepnzw/Lo9CvP/0WSjguMmQy7TZmU7/k1aZeY7naKuMIg7+tf7FpQyyvQ3cZFapkbMDtxUKc86wZj5rKMbm4fl12LmVf610zdNIvKBWduAvCPdPlDYvcyTncIUyptDLPTSuW5spylQBUJHexLFkenVXedabGPDhTFA81l2I3/vG/AsIUAUB/aiLPVkqeLnjxhX0qGkJF2T3tNqvvFRwLCvgSXGX4qvIjzPh5sQ26KtilQSC6w0zsm46m62VBzGVo5Ie0V9G4OaaXOdiyn0kzhuLAzJB7bdrWqAloq3fLN9PudaA3zFuV9AU5DTuEx76vz2iZgTQdvNCd+7AzVcVAAujzqE2TlsEyXeL6fDGFEohlVp2iECUYePq8yvftBapuf7dt7ji6kePeD0slaPFn9rZrF5ChEmMvcY+v+U9j68Zg+KKj/PtECgTf18ipLGv2Io58BuxqmzsKVTxtmkG3PnbrjrtNInEJOFhnka9BfnVUM/46l8Io3vnu9iQf/bJ9Bl3agjfwrE6DBz5a/GsGx1kXVc20H/C0Ap867s5tDPtGT759hOxh+ek/UhahsMZQx3FRD+TpR7NhpWqvl7VUrfUZDvfGSWL A15nY5l8 idrG0ylbdtJ6mPp82efYtVndPlyVZ1KOoBn2e102d+q4G4dS6cvN+p4pzOf+MW/4z3a5TEnsOrXrRRzWW7zMDDw7wDQ5TKDbHRjpekXB3ENWhDCsWgWEZcheJnf2zrXeSeOwaksIrFPUpaocIWOwPJO+/dav+799Y2vBPS7pKR4T4v7+uBalKAWY//zi2XHsrU4ifDr/vIfpuWm55abgRFdOOor0v68zBX9ZE74OSwTYaptBjm8wN8r0HVkqOdEQ6z4yelij2lDQv4Wy/7m5HlWFu2NpwfxpwgysMHw3I6ggCwDU2a/QbJicjl5LdRLBolmyyBx4En1ddwALmwtJiTMfcXwaUmpAO31zPbG5ky8WcHQ5ZyDTXi06SFA== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 > --- > 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) -- Kiryl Shutsemau / Kirill A. Shutemov