From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) (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 8C899462D; Thu, 17 Feb 2022 22:22:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1645136533; x=1676672533; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=ezDIX49Awv6Xk9y+cqp9fwackAICSXYL+qI3anCEO0s=; b=CtwA0GT8A2aQ6fHTKQ8BTjY0cDjgW+mA3Ehj0nC8PXozU2kO8pKC7vwV n+X51wpq9xHAxYgJrFsWnbaVSyWswKDeL1Odw+1oC3COK/LDlUL02LUeE R3O5/QxUxg7IClolZR+ifXbdR5e2e3Z3Nxnqj8mXB8+XTIeZUBeKfZfqW w/7DExsM0kR6ZdkQ2NnWGbGx0fjiQLs4P6E0FHMHoLJSBx7gjZ2aP2rIV 0D7OX76zdzO3jwqNxTAQxU3F4L6WCvJ3AYtJv3imXPZPnL4vvmMktn/Gy eBS/Eq0rK3VavS3cqglLArRLkSwiFIavJiT36nevTQbGBJDIZmQI/RqrY g==; X-IronPort-AV: E=McAfee;i="6200,9189,10261"; a="231623732" X-IronPort-AV: E=Sophos;i="5.88,377,1635231600"; d="scan'208";a="231623732" Received: from fmsmga007.fm.intel.com ([10.253.24.52]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Feb 2022 14:22:10 -0800 X-IronPort-AV: E=Sophos;i="5.88,377,1635231600"; d="scan'208";a="541501681" Received: from adschwah-mobl.amr.corp.intel.com (HELO intel.com) ([10.252.138.69]) by fmsmga007-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 17 Feb 2022 14:22:09 -0800 Date: Thu, 17 Feb 2022 14:22:08 -0800 From: Ben Widawsky To: Dan Williams Cc: linux-cxl@vger.kernel.org, patches@lists.linux.dev, Alison Schofield , Ira Weiny , Jonathan Cameron , Vishal Verma , Bjorn Helgaas , Linux NVDIMM , Linux PCI Subject: Re: [PATCH v5 01/15] cxl/region: Add region creation ABI Message-ID: <20220217222208.f5krwchjljrzjieg@intel.com> References: <20220217171057.685705-1-ben.widawsky@intel.com> <20220217171931.740926-1-ben.widawsky@intel.com> Precedence: bulk X-Mailing-List: nvdimm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On 22-02-17 09:58:04, Dan Williams wrote: > On Thu, Feb 17, 2022 at 9:19 AM Ben Widawsky wrote: > > > > Regions are created as a child of the decoder that encompasses an > > address space with constraints. Regions have a number of attributes that > > must be configured before the region can be activated. > > > > The ABI is not meant to be secure, but is meant to avoid accidental > > races. As a result, a buggy process may create a region by name that was > > allocated by a different process. However, multiple processes which are > > trying not to race with each other shouldn't need special > > synchronization to do so. > > > > // Allocate a new region name > > region=$(cat /sys/bus/cxl/devices/decoder0.0/create_region) > > > > // Create a new region by name > > while > > region=$(cat /sys/bus/cxl/devices/decoder0.0/create_region) > > ! echo $region > /sys/bus/cxl/devices/decoder0.0/create_region > > do true; done > > > > // Region now exists in sysfs > > stat -t /sys/bus/cxl/devices/decoder0.0/$region > > > > // Delete the region, and name > > echo $region > /sys/bus/cxl/devices/decoder0.0/delete_region > > > > Signed-off-by: Ben Widawsky > > Looking good, a few more fixes and cleanups identified below. > > > > > --- > > Changes since v4: > > - Add the missed base attributes addition > > > > --- > > Documentation/ABI/testing/sysfs-bus-cxl | 23 ++ > > .../driver-api/cxl/memory-devices.rst | 11 + > > drivers/cxl/core/Makefile | 1 + > > drivers/cxl/core/core.h | 3 + > > drivers/cxl/core/port.c | 11 + > > drivers/cxl/core/region.c | 213 ++++++++++++++++++ > > drivers/cxl/cxl.h | 5 + > > drivers/cxl/region.h | 23 ++ > > tools/testing/cxl/Kbuild | 1 + > > 9 files changed, 291 insertions(+) > > create mode 100644 drivers/cxl/core/region.c > > create mode 100644 drivers/cxl/region.h > > > > diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl > > index 7c2b846521f3..e5db45ea70ad 100644 > > --- a/Documentation/ABI/testing/sysfs-bus-cxl > > +++ b/Documentation/ABI/testing/sysfs-bus-cxl > > @@ -163,3 +163,26 @@ Description: > > memory (type-3). The 'target_type' attribute indicates the > > current setting which may dynamically change based on what > > memory regions are activated in this decode hierarchy. > > + > > +What: /sys/bus/cxl/devices/decoderX.Y/create_region > > +Date: January, 2022 > > +KernelVersion: v5.18 > > +Contact: linux-cxl@vger.kernel.org > > +Description: > > + Write a value of the form 'regionX.Y:Z' to instantiate a new > > + region within the decode range bounded by decoderX.Y. The value > > + written must match the current value returned from reading this > > + attribute. This behavior lets the kernel arbitrate racing > > + attempts to create a region. The thread that fails to write > > + loops and tries the next value. Regions must be created for root > > + decoders, and must subsequently configured and bound to a region > > + driver before they can be used. > > + > > +What: /sys/bus/cxl/devices/decoderX.Y/delete_region > > +Date: January, 2022 > > +KernelVersion: v5.18 > > +Contact: linux-cxl@vger.kernel.org > > +Description: > > + Deletes the named region. The attribute expects a region in the > > + form "regionX.Y:Z". The region's name, allocated by reading > > + create_region, will also be released. > > diff --git a/Documentation/driver-api/cxl/memory-devices.rst b/Documentation/driver-api/cxl/memory-devices.rst > > index db476bb170b6..66ddc58a21b1 100644 > > --- a/Documentation/driver-api/cxl/memory-devices.rst > > +++ b/Documentation/driver-api/cxl/memory-devices.rst > > @@ -362,6 +362,17 @@ CXL Core > > .. kernel-doc:: drivers/cxl/core/mbox.c > > :doc: cxl mbox > > > > +CXL Regions > > +----------- > > +.. kernel-doc:: drivers/cxl/region.h > > + :identifiers: > > + > > +.. kernel-doc:: drivers/cxl/core/region.c > > + :doc: cxl core region > > + > > +.. kernel-doc:: drivers/cxl/core/region.c > > + :identifiers: > > + > > External Interfaces > > =================== > > > > diff --git a/drivers/cxl/core/Makefile b/drivers/cxl/core/Makefile > > index 6d37cd78b151..39ce8f2f2373 100644 > > --- a/drivers/cxl/core/Makefile > > +++ b/drivers/cxl/core/Makefile > > @@ -4,6 +4,7 @@ obj-$(CONFIG_CXL_BUS) += cxl_core.o > > ccflags-y += -I$(srctree)/drivers/cxl > > cxl_core-y := port.o > > cxl_core-y += pmem.o > > +cxl_core-y += region.o > > cxl_core-y += regs.o > > cxl_core-y += memdev.o > > cxl_core-y += mbox.o > > diff --git a/drivers/cxl/core/core.h b/drivers/cxl/core/core.h > > index 1a50c0fc399c..adfd42370b28 100644 > > --- a/drivers/cxl/core/core.h > > +++ b/drivers/cxl/core/core.h > > @@ -9,6 +9,9 @@ extern const struct device_type cxl_nvdimm_type; > > > > extern struct attribute_group cxl_base_attribute_group; > > > > +extern struct device_attribute dev_attr_create_region; > > +extern struct device_attribute dev_attr_delete_region; > > + > > struct cxl_send_command; > > struct cxl_mem_query_commands; > > int cxl_query_cmd(struct cxl_memdev *cxlmd, > > diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c > > index 1e785a3affaa..860e91cae29b 100644 > > --- a/drivers/cxl/core/port.c > > +++ b/drivers/cxl/core/port.c > > @@ -213,6 +213,8 @@ static struct attribute_group cxl_decoder_base_attribute_group = { > > }; > > > > static struct attribute *cxl_decoder_root_attrs[] = { > > + &dev_attr_create_region.attr, > > + &dev_attr_delete_region.attr, > > &dev_attr_cap_pmem.attr, > > &dev_attr_cap_ram.attr, > > &dev_attr_cap_type2.attr, > > @@ -270,6 +272,8 @@ static void cxl_decoder_release(struct device *dev) > > struct cxl_decoder *cxld = to_cxl_decoder(dev); > > struct cxl_port *port = to_cxl_port(dev->parent); > > > > + ida_free(&cxld->region_ida, cxld->next_region_id); > > + ida_destroy(&cxld->region_ida); > > ida_free(&port->decoder_ida, cxld->id); > > kfree(cxld); > > } > > @@ -1244,6 +1248,13 @@ static struct cxl_decoder *cxl_decoder_alloc(struct cxl_port *port, > > cxld->target_type = CXL_DECODER_EXPANDER; > > cxld->platform_res = (struct resource)DEFINE_RES_MEM(0, 0); > > > > + mutex_init(&cxld->id_lock); > > + ida_init(&cxld->region_ida); > > + rc = ida_alloc(&cxld->region_ida, GFP_KERNEL); > > + if (rc < 0) > > + goto err; > > + > > + cxld->next_region_id = rc; > > return cxld; > > err: > > kfree(cxld); > > diff --git a/drivers/cxl/core/region.c b/drivers/cxl/core/region.c > > new file mode 100644 > > index 000000000000..5576952e4aa1 > > --- /dev/null > > +++ b/drivers/cxl/core/region.c > > @@ -0,0 +1,213 @@ > > +// SPDX-License-Identifier: GPL-2.0-only > > +/* Copyright(c) 2022 Intel Corporation. All rights reserved. */ > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include > > +#include "core.h" > > + > > +/** > > + * DOC: cxl core region > > + * > > + * CXL Regions represent mapped memory capacity in system physical address > > + * space. Whereas the CXL Root Decoders identify the bounds of potential CXL > > + * Memory ranges, Regions represent the active mapped capacity by the HDM > > + * Decoder Capability structures throughout the Host Bridges, Switches, and > > + * Endpoints in the topology. > > + */ > > + > > +static void cxl_region_release(struct device *dev); > > Why forward declare this versus move cxl_region_type after the definition? > > No other CXL object release functions are forward declared. > > > + > > +static const struct device_type cxl_region_type = { > > + .name = "cxl_region", > > + .release = cxl_region_release, > > +}; > > + > > +static struct cxl_region *to_cxl_region(struct device *dev) > > +{ > > + if (dev_WARN_ONCE(dev, dev->type != &cxl_region_type, > > + "not a cxl_region device\n")) > > + return NULL; > > + > > + return container_of(dev, struct cxl_region, dev); > > +} > > + > > +static struct cxl_region *cxl_region_alloc(struct cxl_decoder *cxld) > > +{ > > + struct cxl_region *cxlr; > > + struct device *dev; > > + > > + cxlr = kzalloc(sizeof(*cxlr), GFP_KERNEL); > > + if (!cxlr) > > + return ERR_PTR(-ENOMEM); > > + > > + dev = &cxlr->dev; > > + device_initialize(dev); > > + dev->parent = &cxld->dev; > > + device_set_pm_not_required(dev); > > + dev->bus = &cxl_bus_type; > > + dev->type = &cxl_region_type; > > + > > + return cxlr; > > +} > > + > > +static void unregister_region(void *_cxlr) > > +{ > > + struct cxl_region *cxlr = _cxlr; > > + > > + if (!test_and_set_bit(REGION_DEAD, &cxlr->flags)) > > + device_unregister(&cxlr->dev); > > I thought REGION_DEAD was needed to prevent double > devm_release_action(), not double unregister? > > > +} > > + > > +/** > > + * devm_cxl_add_region - Adds a region to a decoder > > + * @cxld: Parent decoder. > > + * @cxlr: Region to be added to the decoder. > > + * > > + * This is the second step of region initialization. Regions exist within an > > + * address space which is mapped by a @cxld. That @cxld must be a root decoder, > > + * and it enforces constraints upon the region as it is configured. > > + * > > + * Return: 0 if the region was added to the @cxld, else returns negative error > > + * code. The region will be named "regionX.Y.Z" where X is the port, Y is the > > + * decoder id, and Z is the region number. > > + */ > > +static struct cxl_region *devm_cxl_add_region(struct cxl_decoder *cxld) > > +{ > > + struct cxl_port *port = to_cxl_port(cxld->dev.parent); > > + struct cxl_region *cxlr; > > + struct device *dev; > > + int rc; > > + > > + cxlr = cxl_region_alloc(cxld); > > + if (IS_ERR(cxlr)) > > + return cxlr; > > + > > + dev = &cxlr->dev; > > + > > + cxlr->id = cxld->next_region_id; > > + rc = dev_set_name(dev, "region%d.%d:%d", port->id, cxld->id, cxlr->id); > > + if (rc) > > + goto err_out; > > + > > + /* affirm that release will have access to the decoder's region ida */ > > + get_device(&cxld->dev); > > + > > + rc = device_add(dev); > > + if (!rc) > > + rc = devm_add_action_or_reset(port->uport, unregister_region, > > + cxlr); > > + if (rc) > > + goto err_out; > > All the other usages in device_add() in the subsystem follow the style of: > > rc = device_add(dev); > if (rc) > goto err; > > ...any reason to be unique here and indent the success case? > > > > + > > + return cxlr; > > + > > +err_out: > > + put_device(dev); > > + kfree(cxlr); > > This is a double-free of cxlr; > > > + return ERR_PTR(rc); > > +} > > + > > +static ssize_t create_region_show(struct device *dev, > > + struct device_attribute *attr, char *buf) > > +{ > > + struct cxl_port *port = to_cxl_port(dev->parent); > > + struct cxl_decoder *cxld = to_cxl_decoder(dev); > > + > > + return sysfs_emit(buf, "region%d.%d:%d\n", port->id, cxld->id, > > + cxld->next_region_id); > > +} > > + > > +static ssize_t create_region_store(struct device *dev, > > + struct device_attribute *attr, > > + const char *buf, size_t len) > > +{ > > + struct cxl_port *port = to_cxl_port(dev->parent); > > + struct cxl_decoder *cxld = to_cxl_decoder(dev); > > + struct cxl_region *cxlr; > > + int d, p, r, rc = 0; > > + > > + if (sscanf(buf, "region%d.%d:%d", &p, &d, &r) != 3) > > + return -EINVAL; > > + > > + if (port->id != p || cxld->id != d) > > + return -EINVAL; > > + > > + rc = mutex_lock_interruptible(&cxld->id_lock); > > + if (rc) > > + return rc; > > + > > + if (cxld->next_region_id != r) { > > + rc = -EINVAL; > > + goto out; > > + } > > + > > + rc = ida_alloc(&cxld->region_ida, GFP_KERNEL); > > + if (rc < 0) { > > + dev_dbg(dev, "Failed to get next cached id (%d)\n", rc); > > + goto out; > > + } > > + > > + cxlr = devm_cxl_add_region(cxld); > > + if (IS_ERR(cxlr)) { > > + rc = PTR_ERR(cxlr); > > + goto out; > > + } > > + > > + cxld->next_region_id = rc; > > This looks like a leak in the case when devm_cxl_add_region() fails, > so just move it above that call. > It's not super simple with the current pre-caching. If you move this above devm_cxl_add_region(), then you lose the previously pre-cached region. I think the cleaner solution is to just free the ida on failure. Pretty sure no matter what method you go, you need an ida_free in there somewhere. Do you see another way? > > + dev_dbg(dev, "Created %s\n", dev_name(&cxlr->dev)); > > + > > +out: > > + mutex_unlock(&cxld->id_lock); > > + return rc ? rc : len; > > if (rc) > return rc; > return len; > > > +} > > +DEVICE_ATTR_RW(create_region); > > + > > +static struct cxl_region *cxl_find_region_by_name(struct cxl_decoder *cxld, > > + const char *name) > > +{ > > + struct device *region_dev; > > + > > + region_dev = device_find_child_by_name(&cxld->dev, name); > > + if (!region_dev) > > + return ERR_PTR(-ENOENT); > > + > > + return to_cxl_region(region_dev); > > +} > > + > > +static ssize_t delete_region_store(struct device *dev, > > + struct device_attribute *attr, > > + const char *buf, size_t len) > > +{ > > + struct cxl_port *port = to_cxl_port(dev->parent); > > + struct cxl_decoder *cxld = to_cxl_decoder(dev); > > + struct cxl_region *cxlr; > > + > > + cxlr = cxl_find_region_by_name(cxld, buf); > > + if (IS_ERR(cxlr)) > > + return PTR_ERR(cxlr); > > + > > + /* After this, the region is no longer a child of the decoder. */ > > + devm_release_action(port->uport, unregister_region, cxlr); > > This may trigger a WARN in the case where 2 threads race to trigger > the release action. I think the DEAD check is needed to gate this > call, not device_unregister(). > > > + > > + /* Release is likely called here, so cxlr is not safe to reference. */ > > This is always the case with any put_device(), so no need for this comment. > > > + put_device(&cxlr->dev); > > + cxlr = NULL; > > This NULL assignment has no value. > > > + > > + dev_dbg(dev, "Deleted %s\n", buf); > > Not sure a debug statement is needed for something userspace can > directly view itself with the result code from the sysfs write. > > > + return len; > > +} > > +DEVICE_ATTR_WO(delete_region); > > + > > +static void cxl_region_release(struct device *dev) > > +{ > > + struct cxl_decoder *cxld = to_cxl_decoder(dev->parent); > > + struct cxl_region *cxlr = to_cxl_region(dev); > > + > > + dev_dbg(&cxld->dev, "Releasing %s\n", dev_name(dev)); > > + ida_free(&cxld->region_ida, cxlr->id); > > + kfree(cxlr); > > + put_device(&cxld->dev); > > +} > > diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h > > index b4047a310340..d5397f7dfcf4 100644 > > --- a/drivers/cxl/cxl.h > > +++ b/drivers/cxl/cxl.h > > @@ -221,6 +221,8 @@ enum cxl_decoder_type { > > * @target_type: accelerator vs expander (type2 vs type3) selector > > * @flags: memory type capabilities and locking > > * @target_lock: coordinate coherent reads of the target list > > + * @region_ida: allocator for region ids. > > + * @next_region_id: Cached region id for next region. > > * @nr_targets: number of elements in @target > > * @target: active ordered target list in current decoder configuration > > */ > > @@ -236,6 +238,9 @@ struct cxl_decoder { > > enum cxl_decoder_type target_type; > > unsigned long flags; > > seqlock_t target_lock; > > + struct mutex id_lock; > > + struct ida region_ida; > > + int next_region_id; > > int nr_targets; > > struct cxl_dport *target[]; > > }; > > diff --git a/drivers/cxl/region.h b/drivers/cxl/region.h > > new file mode 100644 > > index 000000000000..0016f83bbdfd > > --- /dev/null > > +++ b/drivers/cxl/region.h > > @@ -0,0 +1,23 @@ > > +/* SPDX-License-Identifier: GPL-2.0-only */ > > +/* Copyright(c) 2021 Intel Corporation. */ > > +#ifndef __CXL_REGION_H__ > > +#define __CXL_REGION_H__ > > + > > +#include > > + > > +#include "cxl.h" > > + > > +/** > > + * struct cxl_region - CXL region > > + * @dev: This region's device. > > + * @id: This region's id. Id is globally unique across all regions. > > + * @flags: Flags representing the current state of the region. > > + */ > > +struct cxl_region { > > + struct device dev; > > + int id; > > + unsigned long flags; > > +#define REGION_DEAD 0 > > +}; > > + > > +#endif > > diff --git a/tools/testing/cxl/Kbuild b/tools/testing/cxl/Kbuild > > index 82e49ab0937d..3fe6d34e6d59 100644 > > --- a/tools/testing/cxl/Kbuild > > +++ b/tools/testing/cxl/Kbuild > > @@ -46,6 +46,7 @@ cxl_core-y += $(CXL_CORE_SRC)/memdev.o > > cxl_core-y += $(CXL_CORE_SRC)/mbox.o > > cxl_core-y += $(CXL_CORE_SRC)/pci.o > > cxl_core-y += $(CXL_CORE_SRC)/hdm.o > > +cxl_core-y += $(CXL_CORE_SRC)/region.o > > cxl_core-y += config_check.o > > > > obj-m += test/ > > -- > > 2.35.1 > >