Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752236AbdHPN7I (ORCPT ); Wed, 16 Aug 2017 09:59:08 -0400 Received: from mail.kernel.org ([198.145.29.99]:39484 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751454AbdHPN7F (ORCPT ); Wed, 16 Aug 2017 09:59:05 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 64D4821D4E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=goodmis.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=rostedt@goodmis.org Date: Wed, 16 Aug 2017 09:59:01 -0400 From: Steven Rostedt To: Borislav Petkov Cc: "Luck, Tony" , "Kani, Toshimitsu" , "rjw@rjwysocki.net" , "lenb@kernel.org" , "mchehab@kernel.org" , "linux-kernel@vger.kernel.org" , "linux-acpi@vger.kernel.org" , "linux-edac@vger.kernel.org" Subject: Re: [PATCH v2 4/7] ghes_edac: avoid multiple calls to dmi_walk() Message-ID: <20170816095901.33b0d4c2@gandalf.local.home> In-Reply-To: <20170816082931.p6rpvtlxwt5nccxr@pd.tnic> References: <1502732561.2042.141.camel@hpe.com> <20170814180526.wtfjzgc6uye2qtx6@pd.tnic> <1502734083.2042.143.camel@hpe.com> <20170814183551.sgk2i7lxpmpyodhv@pd.tnic> <1502736750.2042.145.camel@hpe.com> <20170814193432.mjldfhfal5ba5dt7@pd.tnic> <1502741290.2042.147.camel@hpe.com> <20170814203942.6t3mrq3hc324blab@pd.tnic> <1502810766.2042.149.camel@hpe.com> <20170815154815.wy3dqwb4yi3feahg@intel.com> <20170816082931.p6rpvtlxwt5nccxr@pd.tnic> X-Mailer: Claws Mail 3.14.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 7055 Lines: 214 On Wed, 16 Aug 2017 10:29:31 +0200 Borislav Petkov wrote: > --- > diff --git a/drivers/edac/ghes_edac.c b/drivers/edac/ghes_edac.c > index 6f80eb65c26c..a22fabef4791 100644 > --- a/drivers/edac/ghes_edac.c > +++ b/drivers/edac/ghes_edac.c > @@ -28,10 +28,14 @@ struct ghes_edac_pvt { > char msg[80]; > }; > > -static LIST_HEAD(ghes_reglist); > -static DEFINE_MUTEX(ghes_edac_lock); > -static int ghes_edac_mc_num; > +static struct ghes_edac_pvt *ghes_pvt; > > +/* > + * Sync with other, potentially concurrent callers of > + * ghes_edac_report_mem_error(). We don't know what the > + * "inventive" firmware would do. > + */ > +static DEFINE_SPINLOCK(ghes_lock); > > /* Memory Device - Type 17 of SMBIOS spec */ > struct memdev_dmi_entry { > @@ -169,14 +173,11 @@ void ghes_edac_report_mem_error(struct ghes *ghes, int sev, > enum hw_event_mc_err_type type; > struct edac_raw_error_desc *e; > struct mem_ctl_info *mci; > - struct ghes_edac_pvt *pvt = NULL; > + struct ghes_edac_pvt *pvt = ghes_pvt; > + unsigned long flags; > char *p; > u8 grain_bits; > > - list_for_each_entry(pvt, &ghes_reglist, list) { > - if (ghes == pvt->ghes) > - break; > - } > if (!pvt) { > pr_err("Internal error: Can't find EDAC structure\n"); > return; > @@ -398,8 +399,16 @@ void ghes_edac_report_mem_error(struct ghes *ghes, int sev, > (e->page_frame_number << PAGE_SHIFT) | e->offset_in_page, > grain_bits, e->syndrome, pvt->detail_location); > > - /* Report the error via EDAC API */ > + /* > + * We can do the locking below because GHES defers error processing > + * from NMI to IRQ context. Whenever that changes, we'd at least > + * know. > + */ > + WARN_ON_ONCE(in_nmi()); Should the above be: if (WARN_ON_ONCE(in_nmi())) return; To prevent a deadlock? Or do we not care? > + > + spin_lock_irqsave(&ghes_lock, flags); > edac_raw_mc_handle_error(type, mci, e); > + spin_unlock_irqrestore(&ghes_lock, flags); The above looks fine, as long as there's nothing before it that needs synchronization. > } > EXPORT_SYMBOL_GPL(ghes_edac_report_mem_error); > > @@ -409,9 +418,14 @@ int ghes_edac_register(struct ghes *ghes, struct device *dev) > int rc, num_dimm = 0; > struct mem_ctl_info *mci; > struct edac_mc_layer layers[1]; > - struct ghes_edac_pvt *pvt; > struct ghes_edac_dimm_fill dimm_fill; > > + /* > + * We have only one logical memory controller to which all DIMMs belong. > + */ > + if (ghes_pvt) > + return 0; What's the likelihood of two calls to ghes_edac_register being done simultaneously? Because two calls at the same time will get past this. -- Steve > + > /* Get the number of DIMMs */ > dmi_walk(ghes_edac_count_dimms, &num_dimm); > > @@ -425,26 +439,17 @@ int ghes_edac_register(struct ghes *ghes, struct device *dev) > layers[0].size = num_dimm; > layers[0].is_virt_csrow = true; > > - /* > - * We need to serialize edac_mc_alloc() and edac_mc_add_mc(), > - * to avoid duplicated memory controller numbers > - */ > - mutex_lock(&ghes_edac_lock); > - mci = edac_mc_alloc(ghes_edac_mc_num, ARRAY_SIZE(layers), layers, > - sizeof(*pvt)); > + mci = edac_mc_alloc(1, ARRAY_SIZE(layers), layers, sizeof(struct ghes_edac_pvt)); > if (!mci) { > pr_info("Can't allocate memory for EDAC data\n"); > - mutex_unlock(&ghes_edac_lock); > return -ENOMEM; > } > > - pvt = mci->pvt_info; > - memset(pvt, 0, sizeof(*pvt)); > - list_add_tail(&pvt->list, &ghes_reglist); > - pvt->ghes = ghes; > - pvt->mci = mci; > - mci->pdev = dev; > + ghes_pvt = mci->pvt_info; > + ghes_pvt->ghes = ghes; > + ghes_pvt->mci = mci; > > + mci->pdev = dev; > mci->mtype_cap = MEM_FLAG_EMPTY; > mci->edac_ctl_cap = EDAC_FLAG_NONE; > mci->edac_cap = EDAC_FLAG_NONE; > @@ -452,36 +457,23 @@ int ghes_edac_register(struct ghes *ghes, struct device *dev) > mci->ctl_name = "ghes_edac"; > mci->dev_name = "ghes"; > > - if (!ghes_edac_mc_num) { > - if (!fake) { > - pr_info("This EDAC driver relies on BIOS to enumerate memory and get error reports.\n"); > - pr_info("Unfortunately, not all BIOSes reflect the memory layout correctly.\n"); > - pr_info("So, the end result of using this driver varies from vendor to vendor.\n"); > - pr_info("If you find incorrect reports, please contact your hardware vendor\n"); > - pr_info("to correct its BIOS.\n"); > - pr_info("This system has %d DIMM sockets.\n", > - num_dimm); > - } else { > - pr_info("This system has a very crappy BIOS: It doesn't even list the DIMMS.\n"); > - pr_info("Its SMBIOS info is wrong. It is doubtful that the error report would\n"); > - pr_info("work on such system. Use this driver with caution\n"); > - } > + if (!fake) { > + pr_info("This EDAC driver relies on BIOS to enumerate memory and get error reports.\n"); > + pr_info("Unfortunately, not all BIOSes reflect the memory layout correctly.\n"); > + pr_info("So, the end result of using this driver varies from vendor to vendor.\n"); > + pr_info("If you find incorrect reports, please contact your hardware vendor\n"); > + pr_info("to correct its BIOS.\n"); > + pr_info("This system has %d DIMM sockets.\n", num_dimm); > + } else { > + pr_info("This system has a very crappy BIOS: It doesn't even list the DIMMS.\n"); > + pr_info("Its SMBIOS info is wrong. It is doubtful that the error report would\n"); > + pr_info("work on such system. Use this driver with caution\n"); > } > > if (!fake) { > - /* > - * Fill DIMM info from DMI for the memory controller #0 > - * > - * Keep it in blank for the other memory controllers, as > - * there's no reliable way to properly credit each DIMM to > - * the memory controller, as different BIOSes fill the > - * DMI bank location fields on different ways > - */ > - if (!ghes_edac_mc_num) { > - dimm_fill.count = 0; > - dimm_fill.mci = mci; > - dmi_walk(ghes_edac_dmidecode, &dimm_fill); > - } > + dimm_fill.count = 0; > + dimm_fill.mci = mci; > + dmi_walk(ghes_edac_dmidecode, &dimm_fill); > } else { > struct dimm_info *dimm = EDAC_DIMM_PTR(mci->layers, mci->dimms, > mci->n_layers, 0, 0, 0); > @@ -497,12 +489,8 @@ int ghes_edac_register(struct ghes *ghes, struct device *dev) > if (rc < 0) { > pr_info("Can't register at EDAC core\n"); > edac_mc_free(mci); > - mutex_unlock(&ghes_edac_lock); > return -ENODEV; > } > - > - ghes_edac_mc_num++; > - mutex_unlock(&ghes_edac_lock); > return 0; > } > EXPORT_SYMBOL_GPL(ghes_edac_register); > @@ -510,15 +498,9 @@ EXPORT_SYMBOL_GPL(ghes_edac_register); > void ghes_edac_unregister(struct ghes *ghes) > { > struct mem_ctl_info *mci; > - struct ghes_edac_pvt *pvt, *tmp; > - > - list_for_each_entry_safe(pvt, tmp, &ghes_reglist, list) { > - if (ghes == pvt->ghes) { > - mci = pvt->mci; > - edac_mc_del_mc(mci->pdev); > - edac_mc_free(mci); > - list_del(&pvt->list); > - } > - } > + > + mci = ghes_pvt->mci; > + edac_mc_del_mc(mci->pdev); > + edac_mc_free(mci); > } > EXPORT_SYMBOL_GPL(ghes_edac_unregister); >