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Srinivasan" , Haiyang Zhang , Long Li , Andy Lutomirski , linux-doc@vger.kernel.org, linux-hyperv@vger.kernel.org, Nathan Chancellor , Kees Cook , Ashish Kalra Subject: Re: [PATCH v2 2/6] percpu: Bound decrypted storage for all x86 encrypted guests Message-ID: <20260929075426.GQ4120091@noisy.programming.kicks-ass.net> References: <20260929040256.543767-1-zack.rusin@broadcom.com> <20260929040256.543767-3-zack.rusin@broadcom.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260929040256.543767-3-zack.rusin@broadcom.com> X-Stat-Signature: 4iireyiz47bmz74xg1me4igk3fsnx6t5 X-Rspamd-Queue-Id: EFFE240003 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1790668483-393433 X-HE-Meta: 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 uV5gbE3w uqS6BjXfdVVx3WDW8j6GncdEXmFTuZ0AXSyDTFStP7bEqaocfzt/ejlbbSFvj8gm3h8Omgtfh39RPJYXXgl+tkc9iGG+nOV+wxn0gDIVe4utcMsjczsq/LsB/tjEzJ9GYq1YLFuHW1Y5DtvXZhX5JjSRiAxWcA+DGmPNH/hb3NXZDC/feViiUfPIzWcoTP5m6DaQaNTtulgg3XgNmVGIR67fWIRWQQfpGoR6M0AMOLO7Lno6eioaPe6UEakr23OcZd8lu+veQtH7ijFrfNZOynvHjcg== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Sep 29, 2026 at 12:02:51AM -0400, Zack Rusin wrote: > TDX also needs shared per-CPU buffers. Use X86_MEM_ENCRYPT for their > definition and placement, and provide page-aligned boundaries so the > architecture can convert each CPU's whole section before registration. > > Define the boundaries in the SMP template or UP data as appropriate. > Drop the unused DECLARE_PER_CPU_DECRYPTED() macro. > > Suggested-by: Kiryl Shutsemau > Link: https://lore.kernel.org/r/aqqGUAX65s4LdJkr@thinkstation > Signed-off-by: Zack Rusin > --- > include/asm-generic/vmlinux.lds.h | 12 ++++++++---- > include/linux/percpu-defs.h | 7 ++----- > 2 files changed, 10 insertions(+), 9 deletions(-) > > diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h > index 64bc2bfdd2ec..145fcdbbe9db 100644 > --- a/include/asm-generic/vmlinux.lds.h > +++ b/include/asm-generic/vmlinux.lds.h > @@ -1022,11 +1024,13 @@ > * 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 > +#if defined(CONFIG_X86_MEM_ENCRYPT) && defined(CONFIG_SMP) > #define PERCPU_DECRYPTED_SECTION \ > . = ALIGN(PAGE_SIZE); \ > + __start_percpu_decrypted = .; \ > *(.data..percpu..decrypted) \ > - . = ALIGN(PAGE_SIZE); > + . = ALIGN(PAGE_SIZE); \ > + __end_percpu_decrypted = .; > #else > #define PERCPU_DECRYPTED_SECTION > #endif So you're page aligning something that will get different protection and will thus shatter large pages? That is somewhat uncool. We like large pages, large pages are good.