From patchwork Wed Mar 5 10:49:25 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Valentin Schneider X-Patchwork-Id: 871050 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 2506A205E17 for ; Wed, 5 Mar 2025 10:50:26 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741171828; cv=none; b=iDf5jsm/TqyH3zHqyXGuwkNPl2mXHykHrXb7ZQP67uok4y2bu0IvjxnTtaC54Cv2Xwq6IBvj919KyvK/rYwKKe9KbcEzV4j5TjTPpsm6mud2+jJ/RS3+1XPalDMoSH07APDHlA9watX61v4VAOs5Od327XcXds5H0NBSizBCS+I= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741171828; c=relaxed/simple; bh=cmsthhp8/NkuQQkP9C3knJn41ySXxSSKRF4QmJN5Az8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=c58lkKbglL4CK8/1Rd3C9vONixHv4RpY5DXE7W0IABotrAv/67rWk3iNhb4gxIab1iKwwiUaRYaHMXzDfLkIOTB0K4QBMS9tJxmrbxMHQ2BNif8TpCQPWZM5ZW0F2TKP5EDxGa3gYlZsHy9mB3DOKvOeQ2Yt3y2gf/EppYXXRho= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=iMEOw1se; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="iMEOw1se" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1741171826; 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: in-reply-to:in-reply-to:references:references; bh=JwAi6CpDFg+u1P0N2HGLBY5NxvRDUXxSPSsLQo91qeg=; b=iMEOw1seceze+OxI6bXlTnERrReqLdwiHSlipi+csjsFGh6CVw2GKzZ/wqb1nEuvCGGE7Q QI1k7VnM9/odGcVFSYsXrpRVebeVnWRJBBiXl6Lr0x45acstlFB1SorIqXGg5aopmRMRKy zSy3TIDI6fdLzMxc39jNPdTRX+mszLY= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-235-4h_oXHHUPiatPH2cj0OVUQ-1; Wed, 05 Mar 2025 05:50:07 -0500 X-MC-Unique: 4h_oXHHUPiatPH2cj0OVUQ-1 X-Mimecast-MFC-AGG-ID: 4h_oXHHUPiatPH2cj0OVUQ_1741171806 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3770118001CE; Wed, 5 Mar 2025 10:50:05 +0000 (UTC) Received: from vschneid-thinkpadt14sgen2i.remote.csb (unknown [10.44.32.95]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8526B1954B32; Wed, 5 Mar 2025 10:49:58 +0000 (UTC) From: Valentin Schneider To: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rt-users@vger.kernel.org Cc: Mark Rutland , Mike Galbraith , Catalin Marinas , Will Deacon , Peter Collingbourne , Thomas Gleixner , Neeraj Upadhyay , Thiago Jung Bauermann , Mark Brown , Kristina Martsenko , Sebastian Andrzej Siewior , Petr Tesarik , Jinjie Ruan , Juri Lelli , Phil Auld Subject: [PATCH 1/1] arm64: enable PREEMPT_LAZY Date: Wed, 5 Mar 2025 11:49:25 +0100 Message-ID: <20250305104925.189198-2-vschneid@redhat.com> In-Reply-To: <20250305104925.189198-1-vschneid@redhat.com> References: <20250305104925.189198-1-vschneid@redhat.com> Precedence: bulk X-Mailing-List: linux-rt-users@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 From: Mark Rutland For an architecture to enable CONFIG_ARCH_HAS_RESCHED_LAZY, two things are required: 1) Adding a TIF_NEED_RESCHED_LAZY flag definition 2) Checking for TIF_NEED_RESCHED_LAZY in the appropriate locations 2) is handled in a generic manner by CONFIG_GENERIC_ENTRY, which isn't (yet) implemented for arm64. However, outside of core scheduler code, TIF_NEED_RESCHED_LAZY only needs to be checked on a kernel exit, meaning: o return/entry to userspace. o return/entry to guest. The return/entry to a guest is all handled by xfer_to_guest_mode_handle_work() which already does the right thing, so it can be left as-is. arm64 doesn't use common entry's exit_to_user_mode_prepare(), so update its return to user path to check for TIF_NEED_RESCHED_LAZY and call into schedule() accordingly. Link: https://lore.kernel.org/linux-rt-users/20241216190451.1c61977c@mordecai.tesarici.cz/ Link: https://lore.kernel.org/all/xhsmh4j0fl0p3.mognet@vschneid-thinkpadt14sgen2i.remote.csb/ Signed-off-by: Mark Rutland [testdrive, _TIF_WORK_MASK fixlet and changelog.] Signed-off-by: Mike Galbraith [Another round of testing; changelog faff] Signed-off-by: Valentin Schneider --- arch/arm64/Kconfig | 1 + arch/arm64/include/asm/thread_info.h | 16 +++++++++------- arch/arm64/kernel/entry-common.c | 2 +- 3 files changed, 11 insertions(+), 8 deletions(-) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index fcdd0ed3eca89..7789d7fb6f191 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -41,6 +41,7 @@ config ARM64 select ARCH_HAS_NMI_SAFE_THIS_CPU_OPS select ARCH_HAS_NON_OVERLAPPING_ADDRESS_SPACE select ARCH_HAS_NONLEAF_PMD_YOUNG if ARM64_HAFT + select ARCH_HAS_PREEMPT_LAZY select ARCH_HAS_PTE_DEVMAP select ARCH_HAS_PTE_SPECIAL select ARCH_HAS_HW_PTE_YOUNG diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h index 1114c1c3300a1..4443ef2789758 100644 --- a/arch/arm64/include/asm/thread_info.h +++ b/arch/arm64/include/asm/thread_info.h @@ -59,11 +59,12 @@ void arch_setup_new_exec(void); #define TIF_SIGPENDING 0 /* signal pending */ #define TIF_NEED_RESCHED 1 /* rescheduling necessary */ -#define TIF_NOTIFY_RESUME 2 /* callback before returning to user */ -#define TIF_FOREIGN_FPSTATE 3 /* CPU's FP state is not current's */ -#define TIF_UPROBE 4 /* uprobe breakpoint or singlestep */ -#define TIF_MTE_ASYNC_FAULT 5 /* MTE Asynchronous Tag Check Fault */ -#define TIF_NOTIFY_SIGNAL 6 /* signal notifications exist */ +#define TIF_NEED_RESCHED_LAZY 2 /* Lazy rescheduling needed */ +#define TIF_NOTIFY_RESUME 3 /* callback before returning to user */ +#define TIF_FOREIGN_FPSTATE 4 /* CPU's FP state is not current's */ +#define TIF_UPROBE 5 /* uprobe breakpoint or singlestep */ +#define TIF_MTE_ASYNC_FAULT 6 /* MTE Asynchronous Tag Check Fault */ +#define TIF_NOTIFY_SIGNAL 7 /* signal notifications exist */ #define TIF_SYSCALL_TRACE 8 /* syscall trace active */ #define TIF_SYSCALL_AUDIT 9 /* syscall auditing */ #define TIF_SYSCALL_TRACEPOINT 10 /* syscall tracepoint for ftrace */ @@ -85,6 +86,7 @@ void arch_setup_new_exec(void); #define _TIF_SIGPENDING (1 << TIF_SIGPENDING) #define _TIF_NEED_RESCHED (1 << TIF_NEED_RESCHED) +#define _TIF_NEED_RESCHED_LAZY (1 << TIF_NEED_RESCHED_LAZY) #define _TIF_NOTIFY_RESUME (1 << TIF_NOTIFY_RESUME) #define _TIF_FOREIGN_FPSTATE (1 << TIF_FOREIGN_FPSTATE) #define _TIF_SYSCALL_TRACE (1 << TIF_SYSCALL_TRACE) @@ -100,10 +102,10 @@ void arch_setup_new_exec(void); #define _TIF_NOTIFY_SIGNAL (1 << TIF_NOTIFY_SIGNAL) #define _TIF_TSC_SIGSEGV (1 << TIF_TSC_SIGSEGV) -#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \ +#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY | \ _TIF_NOTIFY_RESUME | _TIF_FOREIGN_FPSTATE | \ _TIF_UPROBE | _TIF_MTE_ASYNC_FAULT | \ - _TIF_NOTIFY_SIGNAL) + _TIF_NOTIFY_SIGNAL | _TIF_SIGPENDING) #define _TIF_SYSCALL_WORK (_TIF_SYSCALL_TRACE | _TIF_SYSCALL_AUDIT | \ _TIF_SYSCALL_TRACEPOINT | _TIF_SECCOMP | \ diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c index b260ddc4d3e9a..7993fab0cab4c 100644 --- a/arch/arm64/kernel/entry-common.c +++ b/arch/arm64/kernel/entry-common.c @@ -132,7 +132,7 @@ static void do_notify_resume(struct pt_regs *regs, unsigned long thread_flags) do { local_irq_enable(); - if (thread_flags & _TIF_NEED_RESCHED) + if (thread_flags & (_TIF_NEED_RESCHED | _TIF_NEED_RESCHED_LAZY)) schedule(); if (thread_flags & _TIF_UPROBE)