From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from galois.linutronix.de (Galois.linutronix.de [193.142.43.55]) (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 1CAA72046B3; Sat, 17 May 2025 10:03:04 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=193.142.43.55 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747476186; cv=none; b=HcDAzTLHrCxvxfqef/oiEJPd7xSl92nRZnUHMsd5SxHLct7mW+jAI7ntSORnqEce8HxbNvmYRmI5dkUaqenFGjjradLOSOKvQZJAlnR/yZ/ib/VSTE12GFRq5r3UjxQH/TgCCwJJI+0MGnWUjjlPWzWSk+tHghASRRta0GM+7eE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1747476186; c=relaxed/simple; bh=rGhqyCzEzZax5EfSeEIBuaMGsLguTzGW8pF2+mepZQw=; h=Date:From:To:Subject:Cc:In-Reply-To:References:MIME-Version: Message-ID:Content-Type; b=mKGLr0txWNUF7KAsEiBdKY5M8ft3Wy7ntb3U4z731NBqMKAlWh9jxoFhMEh1Ar0zOjNYYC9bUKpkxinpsurPNOQd45OYEO2PzcerWIHcmFALZqI4bYHnMIIdla43UZ0pOUnQYRsLzVzSN1sJiycVJFBXgeWyWT/Bq7Ayrhhl4sI= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de; spf=pass smtp.mailfrom=linutronix.de; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=gRqpAOyr; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b=HYotn/QS; arc=none smtp.client-ip=193.142.43.55 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linutronix.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linutronix.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="gRqpAOyr"; dkim=permerror (0-bit key) header.d=linutronix.de header.i=@linutronix.de header.b="HYotn/QS" Date: Sat, 17 May 2025 10:03:01 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1747476182; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hDk9rgXrdvRMiJsYj2iDRB29Y4A+pbOWmYLjA5nSTLQ=; b=gRqpAOyrz0zn5EOnTvPnF9OBB9mi9iJIDHgZ8k0QSOqD8Xk3i+0K8ICeHf4oJW+K7TvrXa AT5e7Qs333OFWcJD0xN+BP6G43+MAYCAFOvw9r9GfCBmjjbCdX+ZmWk7TTHLP8XfjIPPsa UbGchbEqD1wfZcQmeKgZ4TXxiWHy4P6vBSQReIdSKXMwFMdQEhw5cS5eyDNEK40nqApLXF 41UFZPLOKoq2XDenlDrRUmpA53HAdJowTn1kOv3OZhrPl2mHLoih4UfEnHSsMpTH4kcmXJ +m79+A0RYO5w1Az4sAez0hlLUO/ILpi7ziJoZM9zat/dH5BDU5kprcNZTmQ8XA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1747476182; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=hDk9rgXrdvRMiJsYj2iDRB29Y4A+pbOWmYLjA5nSTLQ=; b=HYotn/QSbI4VkXx/XfuDqCT3rQP7PNuO38B+jctLRKJwM0KQ2NhejTUuuJWDFL1oJIJVWI 6ND+p7VBzWKAlOCw== From: "tip-bot2 for James Morse" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/cache] x86/resctrl: Resctrl_exit() teardown resctrl but leave the mount point Cc: James Morse , "Borislav Petkov (AMD)" , Shaopeng Tan , Tony Luck , Reinette Chatre , Fenghua Yu , Carl Worth , Peter Newman , Amit Singh Tomar , Shanker Donthineni , Babu Moger , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20250515165855.31452-9-james.morse@arm.com> References: <20250515165855.31452-9-james.morse@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Message-ID: <174747618179.406.8045132395317904616.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails Precedence: bulk Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit The following commit has been merged into the x86/cache branch of tip: Commit-ID: 8c992e24a0627a6ba508184c07766862c8bb3e54 Gitweb: https://git.kernel.org/tip/8c992e24a0627a6ba508184c07766862c8bb3e54 Author: James Morse AuthorDate: Thu, 15 May 2025 16:58:38 Committer: Borislav Petkov (AMD) CommitterDate: Thu, 15 May 2025 21:04:49 +02:00 x86/resctrl: Resctrl_exit() teardown resctrl but leave the mount point resctrl_exit() was intended for use when the 'resctrl' module was unloaded. resctrl can't be built as a module, and the kernfs helpers are not exported so this is unlikely to change. MPAM has an error interrupt which indicates the MPAM driver has gone haywire. Should this occur tasks could run with the wrong control values, leading to bad performance for important tasks. In this scenario the MPAM driver will reset the hardware, but it needs a way to tell resctrl that no further configuration should be attempted. In particular, moving tasks between control or monitor groups does not interact with the architecture code, so there is no opportunity for the arch code to indicate that the hardware is no-longer functioning. Using resctrl_exit() for this leaves the system in a funny state as resctrl is still mounted, but cannot be un-mounted because the sysfs directory that is typically used has been removed. Dave Martin suggests this may cause systemd trouble in the future as not all filesystems can be unmounted. Add calls to remove all the files and directories in resctrl, and remove the sysfs_remove_mount_point() call that leaves the system in a funny state. When triggered, this causes all the resctrl files to disappear. resctrl can be unmounted, but not mounted again. Signed-off-by: James Morse Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Shaopeng Tan Reviewed-by: Tony Luck Reviewed-by: Reinette Chatre Reviewed-by: Fenghua Yu Tested-by: Fenghua Yu Tested-by: Carl Worth # arm64 Tested-by: Shaopeng Tan Tested-by: Peter Newman Tested-by: Amit Singh Tomar # arm64 Tested-by: Shanker Donthineni # arm64 Tested-by: Babu Moger Tested-by: Tony Luck Link: https://lore.kernel.org/20250515165855.31452-9-james.morse@arm.com --- arch/x86/kernel/cpu/resctrl/rdtgroup.c | 48 ++++++++++++++++++++----- 1 file changed, 40 insertions(+), 8 deletions(-) diff --git a/arch/x86/kernel/cpu/resctrl/rdtgroup.c b/arch/x86/kernel/cpu/resctrl/rdtgroup.c index 29f76ad..1e48c61 100644 --- a/arch/x86/kernel/cpu/resctrl/rdtgroup.c +++ b/arch/x86/kernel/cpu/resctrl/rdtgroup.c @@ -3078,6 +3078,22 @@ static void rmdir_all_sub(void) kernfs_remove(kn_mondata); } +static void resctrl_fs_teardown(void) +{ + lockdep_assert_held(&rdtgroup_mutex); + + /* Cleared by rdtgroup_destroy_root() */ + if (!rdtgroup_default.kn) + return; + + rmdir_all_sub(); + rdt_pseudo_lock_release(); + rdtgroup_default.mode = RDT_MODE_SHAREABLE; + closid_exit(); + schemata_list_destroy(); + rdtgroup_destroy_root(); +} + static void rdt_kill_sb(struct super_block *sb) { struct rdt_resource *r; @@ -3091,12 +3107,7 @@ static void rdt_kill_sb(struct super_block *sb) for_each_alloc_capable_rdt_resource(r) resctrl_arch_reset_all_ctrls(r); - rmdir_all_sub(); - rdt_pseudo_lock_release(); - rdtgroup_default.mode = RDT_MODE_SHAREABLE; - closid_exit(); - schemata_list_destroy(); - rdtgroup_destroy_root(); + resctrl_fs_teardown(); if (resctrl_arch_alloc_capable()) resctrl_arch_disable_alloc(); if (resctrl_arch_mon_capable()) @@ -4127,6 +4138,8 @@ static int rdtgroup_setup_root(struct rdt_fs_context *ctx) static void rdtgroup_destroy_root(void) { + lockdep_assert_held(&rdtgroup_mutex); + kernfs_destroy_root(rdt_root); rdtgroup_default.kn = NULL; } @@ -4441,23 +4454,42 @@ static bool __exit resctrl_online_domains_exist(void) return false; } -/* +/** * resctrl_exit() - Remove the resctrl filesystem and free resources. * + * Called by the architecture code in response to a fatal error. + * Removes resctrl files and structures from kernfs to prevent further + * configuration. + * * When called by the architecture code, all CPUs and resctrl domains must be * offline. This ensures the limbo and overflow handlers are not scheduled to * run, meaning the data structures they access can be freed by * resctrl_mon_resource_exit(). + * + * After resctrl_exit() returns, the architecture code should return an + * error from all resctrl_arch_ functions that can do this. + * resctrl_arch_get_resource() must continue to return struct rdt_resources + * with the correct rid field to ensure the filesystem can be unmounted. */ void __exit resctrl_exit(void) { cpus_read_lock(); WARN_ON_ONCE(resctrl_online_domains_exist()); + + mutex_lock(&rdtgroup_mutex); + resctrl_fs_teardown(); + mutex_unlock(&rdtgroup_mutex); + cpus_read_unlock(); debugfs_remove_recursive(debugfs_resctrl); + debugfs_resctrl = NULL; unregister_filesystem(&rdt_fs_type); - sysfs_remove_mount_point(fs_kobj, "resctrl"); + + /* + * Do not remove the sysfs mount point added by resctrl_init() so that + * it can be used to umount resctrl. + */ resctrl_mon_resource_exit(); }