From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-178.mta0.migadu.com (out-178.mta0.migadu.com [91.218.175.178]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8CD252DCBEC for ; Sun, 14 Sep 2025 15:57:42 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.178 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757865466; cv=none; b=l7R8wBso22rJ3/4t3p4nLCLcXFmhVYK9QuayhMEHsEW/fU51PZrGB7/iQ9jE3zIJkxTsO6DeCWKuEH+e+05VQBS6aF5l4h6xKRXeWcE0Bg3yCYYCc/XGGRDhXfQjKljr5JcnfH7F4iB1YsKYfJ72VTCJvrvKlyY+mwhvc0hruOA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757865466; c=relaxed/simple; bh=ovATHq/uskUjDJ27oWtebFVNFc+1HJG88zQ5ljax67s=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=Gyx3OXNRKABi83yQ+BvPTmr+4sOM+xs7QFVxQ/KMeGAR98Tkfbvi3h4DcXQnHyuQ++rbCXPg8ApH34W3emJEswj5bwtqsr1OdbPnmdbf56gdd//WqVZKQegjIKRzbrKq9nvg6MYuTpriP2zRY6ToUZrJsv6AK6TGJX+sbBe+osg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=YF42nSy7; arc=none smtp.client-ip=91.218.175.178 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="YF42nSy7" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1757865460; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=oZx0OuUKUc0dBSWHMmkZJf76LNudilRN4lNfCv6pOS0=; b=YF42nSy7QSo4QeKLpOwwHEiN5aSH6qGid/Xzc/YNKaTVISQYWz4E3wQ3RQtYjYf9ZxpPJQ mBkk1vwHeDfOvUeAd780czfDVRlFBYFqAhilna8K6GnFSBQnD7tTCjBH+A6r80yhuwINCP my+7HjOA+gVDnGZF8IIY8FoWJWJcgvA= From: Tiwei Bie To: richard@nod.at, anton.ivanov@cambridgegreys.com, johannes@sipsolutions.net Cc: linux-um@lists.infradead.org, linux-kernel@vger.kernel.org, benjamin@sipsolutions.net, arnd@arndb.de, tiwei.btw@antgroup.com, tiwei.bie@linux.dev Subject: [PATCH v3 0/7] um: Add SMP support Date: Sun, 14 Sep 2025 23:56:51 +0800 Message-Id: <20250914155658.1028790-1-tiwei.bie@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Tiwei Bie This series adds initial symmetric multi-processing (SMP) support to UML. With this support, it is now possible for users to tell UML to start multiple virtual CPUs, each represented as a separate host thread. In UML, kthreads and normal threads (when running in kernel mode) can be scheduled and executed simultaneously on different virtual CPUs. However, the userspace code of normal threads currently still runs within their respective single-threaded stubs. So SMP within the kernel is supported. SMP across different processes in userspace is also supported. Currently, the limitation is that multi-threading within the same process does not yet support true SMP in userspace, because it would require converting the stub into a multi-threaded implementation, which is not covered in this series. Extending the stub to support true SMP in userspace within the same process could be done later and requires careful design. It may be better to handle it in a follow-up series. Here are some steps to try out SMP support in UML: 1. Build UML with CONFIG_SMP=y and, for example, CONFIG_NR_CPUS=8. 2. Launch a UML instance with, for example, 8 virtual CPUs. $ ./linux mem=16G ncpus=8 seccomp=on init=/bin/sh ubd0=$your_rootfs_image v3: - Fix need_resched based idle sleep; (Johannes) - Remove getcpu support from the vdso on UML/x86; (Johannes) - Describe 'cpu' parameter of os_timer_disable; (lkp@intel.com) - Misc fixes and cleanups; v2 (https://lore.kernel.org/all/20250810055136.897712-1-tiwei.bie@linux.dev/): - Implement IPI based on RT signal; (Johannes) - Fix raw_smp_processor_id() for non-SMP case; (Johannes) - Add sparse check for turnstile; (Johannes) - Implement spinlock in $SUBARCH; - Fix potential race on stub's siginfo; - Rewrite AP bring-up (e.g. switch to generic idle thread); - Misc fixes and cleanups; v1: https://lore.kernel.org/all/20250727062937.1369050-1-tiwei.bie@linux.dev/ RFC: https://lore.kernel.org/all/20250713172536.404809-1-tiwei.bie@linux.dev/ Tiwei Bie (7): um: Turn signals_* into thread-local variables um: Determine sleep based on need_resched() um: Define timers on a per-CPU basis um: Add initial SMP support um: vdso: Remove getcpu support on x86 asm-generic: percpu: Add assembly guard um: Enable SMP support on x86 .../core/generic-idle-thread/arch-support.txt | 2 +- arch/um/Kconfig | 46 +++- arch/um/include/asm/current.h | 5 +- arch/um/include/asm/hardirq.h | 24 +- arch/um/include/asm/irqflags.h | 4 +- arch/um/include/asm/mmu.h | 10 + arch/um/include/asm/pgtable.h | 2 + arch/um/include/asm/smp.h | 15 +- arch/um/include/linux/smp-internal.h | 17 ++ arch/um/include/linux/time-internal.h | 3 + arch/um/include/shared/kern_util.h | 2 + arch/um/include/shared/longjmp.h | 3 +- arch/um/include/shared/os.h | 24 +- arch/um/include/shared/skas/mm_id.h | 5 + arch/um/include/shared/smp.h | 20 ++ arch/um/kernel/Makefile | 1 + arch/um/kernel/irq.c | 27 +- arch/um/kernel/ksyms.c | 2 +- arch/um/kernel/mem.c | 2 + arch/um/kernel/process.c | 17 +- arch/um/kernel/skas/mmu.c | 33 ++- arch/um/kernel/skas/process.c | 7 +- arch/um/kernel/smp.c | 241 ++++++++++++++++++ arch/um/kernel/time.c | 58 +++-- arch/um/kernel/tlb.c | 5 +- arch/um/kernel/trap.c | 2 +- arch/um/kernel/um_arch.c | 25 +- arch/um/os-Linux/Makefile | 4 +- arch/um/os-Linux/internal.h | 13 + arch/um/os-Linux/main.c | 5 +- arch/um/os-Linux/process.c | 20 ++ arch/um/os-Linux/signal.c | 46 +++- arch/um/os-Linux/skas/process.c | 22 +- arch/um/os-Linux/smp.c | 148 +++++++++++ arch/um/os-Linux/start_up.c | 4 + arch/um/os-Linux/time.c | 78 ++++-- arch/x86/um/Kconfig | 3 + arch/x86/um/asm/spinlock.h | 8 + arch/x86/um/vdso/um_vdso.c | 20 -- arch/x86/um/vdso/vdso.lds.S | 2 - include/asm-generic/percpu.h | 3 + 41 files changed, 870 insertions(+), 108 deletions(-) create mode 100644 arch/um/include/linux/smp-internal.h create mode 100644 arch/um/include/shared/smp.h create mode 100644 arch/um/kernel/smp.c create mode 100644 arch/um/os-Linux/smp.c create mode 100644 arch/x86/um/asm/spinlock.h base-commit: e66ae377fe219c98d3d5b8a0d35da4413a5390ca -- 2.34.1