From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 57135C35280 for ; Thu, 7 May 2020 23:55:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3AAB420735 for ; Thu, 7 May 2020 23:55:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726509AbgEGXzj (ORCPT ); Thu, 7 May 2020 19:55:39 -0400 Received: from mga01.intel.com ([192.55.52.88]:2515 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726476AbgEGXzj (ORCPT ); Thu, 7 May 2020 19:55:39 -0400 IronPort-SDR: e6P0vGUWLOvoFYXEEZSYPLpgQwOp/tJMz0R8LydBFHF0cfdynH7avQAgmSTSyyQY25S7bGQhO2 rPvg/1tZwLoA== X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga101.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 May 2020 16:55:31 -0700 IronPort-SDR: ka+TMz8D+wZX+awfx1R69MtBaIv58Pi9zH33FF2popoTwztxUaRb2E+qUdIlSDpbThN0/cL/rW f8d3NyYtFNIA== X-IronPort-AV: E=Sophos;i="5.73,365,1583222400"; d="scan'208";a="285189036" Received: from dwillia2-desk3.jf.intel.com (HELO dwillia2-desk3.amr.corp.intel.com) ([10.54.39.16]) by fmsmga004-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 07 May 2020 16:55:31 -0700 Subject: [PATCH v2] ACPI: Drop rcu usage for MMIO mappings From: Dan Williams To: rafael.j.wysocki@intel.com Cc: stable@vger.kernel.org, Len Brown , Borislav Petkov , Ira Weiny , James Morse , Erik Kaneda , Myron Stowe , "Rafael J. Wysocki" , Andy Shevchenko , linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linux-nvdimm@lists.01.org Date: Thu, 07 May 2020 16:39:20 -0700 Message-ID: <158889473309.2292982.18007035454673387731.stgit@dwillia2-desk3.amr.corp.intel.com> User-Agent: StGit/0.18-3-g996c MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-acpi-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org Recently a performance problem was reported for a process invoking a non-trival ASL program. The method call in this case ends up repetitively triggering a call path like: acpi_ex_store acpi_ex_store_object_to_node acpi_ex_write_data_to_field acpi_ex_insert_into_field acpi_ex_write_with_update_rule acpi_ex_field_datum_io acpi_ex_access_region acpi_ev_address_space_dispatch acpi_ex_system_memory_space_handler acpi_os_map_cleanup.part.14 _synchronize_rcu_expedited.constprop.89 schedule The end result of frequent synchronize_rcu_expedited() invocation is tiny sub-millisecond spurts of execution where the scheduler freely migrates this apparently sleepy task. The overhead of frequent scheduler invocation multiplies the execution time by a factor of 2-3X. For example, performance improves from 16 minutes to 7 minutes for a firmware update procedure across 24 devices. Perhaps the rcu usage was intended to allow for not taking a sleeping lock in the acpi_os_{read,write}_memory() path which ostensibly could be called from an APEI NMI error interrupt? Neither rcu_read_lock() nor ioremap() are interrupt safe, so add a WARN_ONCE() to validate that rcu was not serving as a mechanism to avoid direct calls to ioremap(). Even the original implementation had a spin_lock_irqsave(), but that is not NMI safe. APEI itself already has some concept of avoiding ioremap() from interrupt context (see erst_exec_move_data()), if the new warning triggers it means that APEI either needs more instrumentation like that to pre-emptively fail, or more infrastructure to arrange for pre-mapping the resources it needs in NMI context. Cc: Fixes: 620242ae8c3d ("ACPI: Maintain a list of ACPI memory mapped I/O remappings") Cc: Len Brown Cc: Borislav Petkov Cc: Ira Weiny Cc: James Morse Cc: Erik Kaneda Cc: Myron Stowe Cc: "Rafael J. Wysocki" Cc: Andy Shevchenko Signed-off-by: Dan Williams --- Changes since v1 [1]: - Actually cc: the most important list for ACPI changes (Rafael) - Cleanup unnecessary variable initialization (Andy) Link: https://lore.kernel.org/linux-nvdimm/158880834905.2183490.15616329469420234017.stgit@dwillia2-desk3.amr.corp.intel.com/ drivers/acpi/osl.c | 117 +++++++++++++++++++++++++--------------------------- 1 file changed, 57 insertions(+), 60 deletions(-) diff --git a/drivers/acpi/osl.c b/drivers/acpi/osl.c index 762c5d50b8fe..a44b75aac5d0 100644 --- a/drivers/acpi/osl.c +++ b/drivers/acpi/osl.c @@ -214,13 +214,13 @@ acpi_physical_address __init acpi_os_get_root_pointer(void) return pa; } -/* Must be called with 'acpi_ioremap_lock' or RCU read lock held. */ static struct acpi_ioremap * acpi_map_lookup(acpi_physical_address phys, acpi_size size) { struct acpi_ioremap *map; - list_for_each_entry_rcu(map, &acpi_ioremaps, list, acpi_ioremap_lock_held()) + lockdep_assert_held(&acpi_ioremap_lock); + list_for_each_entry(map, &acpi_ioremaps, list) if (map->phys <= phys && phys + size <= map->phys + map->size) return map; @@ -228,7 +228,6 @@ acpi_map_lookup(acpi_physical_address phys, acpi_size size) return NULL; } -/* Must be called with 'acpi_ioremap_lock' or RCU read lock held. */ static void __iomem * acpi_map_vaddr_lookup(acpi_physical_address phys, unsigned int size) { @@ -263,7 +262,8 @@ acpi_map_lookup_virt(void __iomem *virt, acpi_size size) { struct acpi_ioremap *map; - list_for_each_entry_rcu(map, &acpi_ioremaps, list, acpi_ioremap_lock_held()) + lockdep_assert_held(&acpi_ioremap_lock); + list_for_each_entry(map, &acpi_ioremaps, list) if (map->virt <= virt && virt + size <= map->virt + map->size) return map; @@ -360,7 +360,7 @@ void __iomem __ref map->size = pg_sz; map->refcount = 1; - list_add_tail_rcu(&map->list, &acpi_ioremaps); + list_add_tail(&map->list, &acpi_ioremaps); out: mutex_unlock(&acpi_ioremap_lock); @@ -374,20 +374,13 @@ void *__ref acpi_os_map_memory(acpi_physical_address phys, acpi_size size) } EXPORT_SYMBOL_GPL(acpi_os_map_memory); -/* Must be called with mutex_lock(&acpi_ioremap_lock) */ -static unsigned long acpi_os_drop_map_ref(struct acpi_ioremap *map) -{ - unsigned long refcount = --map->refcount; - - if (!refcount) - list_del_rcu(&map->list); - return refcount; -} - -static void acpi_os_map_cleanup(struct acpi_ioremap *map) +static void acpi_os_drop_map_ref(struct acpi_ioremap *map) { - synchronize_rcu_expedited(); + lockdep_assert_held(&acpi_ioremap_lock); + if (--map->refcount > 0) + return; acpi_unmap(map->phys, map->virt); + list_del(&map->list); kfree(map); } @@ -408,7 +401,6 @@ static void acpi_os_map_cleanup(struct acpi_ioremap *map) void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size) { struct acpi_ioremap *map; - unsigned long refcount; if (!acpi_permanent_mmap) { __acpi_unmap_table(virt, size); @@ -422,11 +414,8 @@ void __ref acpi_os_unmap_iomem(void __iomem *virt, acpi_size size) WARN(true, PREFIX "%s: bad address %p\n", __func__, virt); return; } - refcount = acpi_os_drop_map_ref(map); + acpi_os_drop_map_ref(map); mutex_unlock(&acpi_ioremap_lock); - - if (!refcount) - acpi_os_map_cleanup(map); } EXPORT_SYMBOL_GPL(acpi_os_unmap_iomem); @@ -461,7 +450,6 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas) { u64 addr; struct acpi_ioremap *map; - unsigned long refcount; if (gas->space_id != ACPI_ADR_SPACE_SYSTEM_MEMORY) return; @@ -477,11 +465,8 @@ void acpi_os_unmap_generic_address(struct acpi_generic_address *gas) mutex_unlock(&acpi_ioremap_lock); return; } - refcount = acpi_os_drop_map_ref(map); + acpi_os_drop_map_ref(map); mutex_unlock(&acpi_ioremap_lock); - - if (!refcount) - acpi_os_map_cleanup(map); } EXPORT_SYMBOL(acpi_os_unmap_generic_address); @@ -700,55 +685,71 @@ int acpi_os_read_iomem(void __iomem *virt_addr, u64 *value, u32 width) return 0; } +static void __iomem *acpi_os_rw_map(acpi_physical_address phys_addr, + unsigned int size, bool *did_fallback) +{ + void __iomem *virt_addr; + + if (WARN_ONCE(in_interrupt(), "ioremap in interrupt context\n")) + return NULL; + + /* Try to use a cached mapping and fallback otherwise */ + *did_fallback = false; + mutex_lock(&acpi_ioremap_lock); + virt_addr = acpi_map_vaddr_lookup(phys_addr, size); + if (virt_addr) + return virt_addr; + mutex_unlock(&acpi_ioremap_lock); + + virt_addr = acpi_os_ioremap(phys_addr, size); + *did_fallback = true; + + return virt_addr; +} + +static void acpi_os_rw_unmap(void __iomem *virt_addr, bool did_fallback) +{ + if (did_fallback) { + /* in the fallback case no lock is held */ + iounmap(virt_addr); + return; + } + + mutex_unlock(&acpi_ioremap_lock); +} + acpi_status acpi_os_read_memory(acpi_physical_address phys_addr, u64 *value, u32 width) { - void __iomem *virt_addr; unsigned int size = width / 8; - bool unmap = false; + bool did_fallback = false; + void __iomem *virt_addr; u64 dummy; int error; - rcu_read_lock(); - virt_addr = acpi_map_vaddr_lookup(phys_addr, size); - if (!virt_addr) { - rcu_read_unlock(); - virt_addr = acpi_os_ioremap(phys_addr, size); - if (!virt_addr) - return AE_BAD_ADDRESS; - unmap = true; - } - + virt_addr = acpi_os_rw_map(phys_addr, size, &did_fallback); + if (!virt_addr) + return AE_BAD_ADDRESS; if (!value) value = &dummy; error = acpi_os_read_iomem(virt_addr, value, width); BUG_ON(error); - if (unmap) - iounmap(virt_addr); - else - rcu_read_unlock(); - + acpi_os_rw_unmap(virt_addr, did_fallback); return AE_OK; } acpi_status acpi_os_write_memory(acpi_physical_address phys_addr, u64 value, u32 width) { - void __iomem *virt_addr; unsigned int size = width / 8; - bool unmap = false; + bool did_fallback = false; + void __iomem *virt_addr; - rcu_read_lock(); - virt_addr = acpi_map_vaddr_lookup(phys_addr, size); - if (!virt_addr) { - rcu_read_unlock(); - virt_addr = acpi_os_ioremap(phys_addr, size); - if (!virt_addr) - return AE_BAD_ADDRESS; - unmap = true; - } + virt_addr = acpi_os_rw_map(phys_addr, size, &did_fallback); + if (!virt_addr) + return AE_BAD_ADDRESS; switch (width) { case 8: @@ -767,11 +768,7 @@ acpi_os_write_memory(acpi_physical_address phys_addr, u64 value, u32 width) BUG(); } - if (unmap) - iounmap(virt_addr); - else - rcu_read_unlock(); - + acpi_os_rw_unmap(virt_addr, did_fallback); return AE_OK; }