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Tue, 03 Feb 2026 18:28:33 -0800 (PST) Received: by ikb-h07-29-noble.in.iijlab.net (Postfix, from userid 1010) id 523EE1200C45; Wed, 4 Feb 2026 11:28:32 +0900 (JST) From: Hajime Tazaki To: linux-um@lists.infradead.org Cc: thehajime@gmail.com, ricarkol@google.com, Liam.Howlett@oracle.com, linux-kernel@vger.kernel.org Subject: [PATCH v14 11/13] um: nommu: disable SMP on nommu UML Date: Wed, 4 Feb 2026 11:28:09 +0900 Message-ID: <3b9e3e4b85c9bdbc4e1fdd123c8270652a88e1e9.1770170302.git.thehajime@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" CONFIG_SMP doesn't work with nommu UML since fs register handling of host does conflict with thread local storage (more specifically, the variable signals_enabled). Thus this commit disables the CONFIG option and the TLS variables. Signed-off-by: Hajime Tazaki --- arch/um/os-Linux/internal.h | 8 ++++++++ arch/x86/um/Kconfig | 2 +- 2 files changed, 9 insertions(+), 1 deletion(-) diff --git a/arch/um/os-Linux/internal.h b/arch/um/os-Linux/internal.h index bac9fcc8c14c..25cb5cc931c1 100644 --- a/arch/um/os-Linux/internal.h +++ b/arch/um/os-Linux/internal.h @@ -6,6 +6,14 @@ #include #include =20 +/* NOMMU doesn't work with thread-local storage used in CONFIG_SMP, + * due to the dependency on host_fs variable switch upon user/kernel + * context so, disable TLS until NOMMU supports SMP. + */ +#ifndef CONFIG_MMU +#define __thread +#endif + /* * elf_aux.c */ diff --git a/arch/x86/um/Kconfig b/arch/x86/um/Kconfig index bdd7c8e39b01..f12e2e4e0a12 100644 --- a/arch/x86/um/Kconfig +++ b/arch/x86/um/Kconfig @@ -12,7 +12,7 @@ config UML_X86 select ARCH_USE_QUEUED_SPINLOCKS select DCACHE_WORD_ACCESS select HAVE_EFFICIENT_UNALIGNED_ACCESS - select UML_SUBARCH_SUPPORTS_SMP if X86_CX8 + select UML_SUBARCH_SUPPORTS_SMP if X86_CX8 && MMU =20 config 64BIT bool "64-bit kernel" if "$(SUBARCH)" =3D "x86" --=20 2.43.0