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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8DE27C433F5 for ; Thu, 17 Feb 2022 23:50:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229605AbiBQXu4 (ORCPT ); Thu, 17 Feb 2022 18:50:56 -0500 Received: from gmail-smtp-in.l.google.com ([23.128.96.19]:49344 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229623AbiBQXuy (ORCPT ); Thu, 17 Feb 2022 18:50:54 -0500 Received: from mail-il1-x130.google.com (mail-il1-x130.google.com [IPv6:2607:f8b0:4864:20::130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 64523433BE for ; Thu, 17 Feb 2022 15:50:38 -0800 (PST) Received: by mail-il1-x130.google.com with SMTP id d7so3459395ilf.8 for ; Thu, 17 Feb 2022 15:50:38 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20210112.gappssmtp.com; s=20210112; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=u4jK6zM/dGsbBGtsbu+DwrbOk29KN2o86uMbiSzfAK0=; b=az7hZKDGRAkoXQBEkYUWpj0gH0gHol0LQpBS5h8fK7OCa8iMwXhiDL6Z23Q34GHwkT P05dl6MAjq6cFUvwju3EGm5VtVtBGuYPtbvB9AGuvIPfnL4UWJZXU+CQ6VgffIgFY3Qo DYKSu07MMz6BNzbRis8o4MTmnL09N1j3s/YJt5MCubbJ6DWeD5RZsP5dBcdOQL3dM3rS a4F4u3wFv/XQr7+zy9JjoUuBa96p/i+ix2LggTC2gPdLJ9zwgj5y0UxDYO2xNlqdT+jw 5N/8Jmn2p1LhtH2C7uCcp84Q6GFLve7QfuP7k/CStbxEAMM7qC7WU++SrkV0htgoI6CK z2Tw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=u4jK6zM/dGsbBGtsbu+DwrbOk29KN2o86uMbiSzfAK0=; b=xdLRvKoZc5sWBY1LhRO832VnIo7A97U00EQQG/Zrx3Lls8YLBIZE49aeZjBlDYLQ6i IpGwP/fuI+YsscYrc9Tvcsh9p4zrNHnZxLEuN+ISXAZEyisR5ivnX9zFVRajcwMIfkGr /DXS9gkXWtxBPWEeCqMR4PDKDbFLPDvAzafC/RP8at+HUpybfslC8Mjn+GniRYFDg22d 9ncwnvldhXWDHi55bqNGMtjLHa9tEG0bXRbg/peSmLRQ4r2E7N+jzLBxzi9cYq+oGMgM NR7K7K53A8As1F4xy3EAdFWY2X2FDcmOaXmURrdfeKwDXK+yDIXNoUm2NkBornfjRQtt hOAQ== X-Gm-Message-State: AOAM530RlYGg1abaz5uMLcl+stmPWd1jvnHsc33AM0Wd3nKAMgmHHmih 2nOdLQF1NlfOD5bFva7yyHecTsVGfFqv166BfR8ZA43lYFcnSA== X-Google-Smtp-Source: ABdhPJwE+OIl8dV3jNoTmCdOxGcrp8lf33cuW1poct8jXzYwVoRqBZaGpYL+5c/kdmQjFLr7LKt61ymLRq1nG0nNp+I= X-Received: by 2002:a63:2354:0:b0:372:c945:bfd1 with SMTP id u20-20020a632354000000b00372c945bfd1mr4110168pgm.437.1645140775197; Thu, 17 Feb 2022 15:32:55 -0800 (PST) MIME-Version: 1.0 References: <20220217171057.685705-1-ben.widawsky@intel.com> <20220217171931.740926-1-ben.widawsky@intel.com> <20220217222208.f5krwchjljrzjieg@intel.com> In-Reply-To: <20220217222208.f5krwchjljrzjieg@intel.com> From: Dan Williams Date: Thu, 17 Feb 2022 15:32:44 -0800 Message-ID: Subject: Re: [PATCH v5 01/15] cxl/region: Add region creation ABI To: Ben Widawsky Cc: linux-cxl@vger.kernel.org, patches@lists.linux.dev, Alison Schofield , Ira Weiny , Jonathan Cameron , Vishal Verma , Bjorn Helgaas , Linux NVDIMM , Linux PCI Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Thu, Feb 17, 2022 at 2:22 PM Ben Widawsky wrote: > > 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? As soon as one thread has successfully acquired the next_region_id then it is safe to advance and assume that the devm_cxl_add_region() owns releasing that id. In fact, just make that implicit. Move the ida_alloc() and the next_region_id advancement internal to cxl_region_alloc() with a device_lock_assert() for the id_lock. Then the recovery of the allocated id happens naturally like all the other ids in the subsystem i.e. at release time.