Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752119AbdGAUKd (ORCPT ); Sat, 1 Jul 2017 16:10:33 -0400 Received: from mail-yb0-f172.google.com ([209.85.213.172]:36827 "EHLO mail-yb0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751940AbdGAUKc (ORCPT ); Sat, 1 Jul 2017 16:10:32 -0400 MIME-Version: 1.0 In-Reply-To: References: <293ee143dcabb386ca06b384a384171c256a2ecc.1498810220.git.jerry.hoemann@hpe.com> <20170701195805.GA13259@anatevka.americas.hpqcorp.net> From: Dan Williams Date: Sat, 1 Jul 2017 13:10:31 -0700 Message-ID: Subject: Re: [PATCH v4 3/6] libnvdimm, acpi, nfit: Add bus level dsm mask for pass thru. To: Jerry Hoemann Cc: "linux-nvdimm@lists.01.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2532 Lines: 54 On Sat, Jul 1, 2017 at 1:08 PM, Dan Williams wrote: > On Sat, Jul 1, 2017 at 12:58 PM, Jerry Hoemann wrote: >> On Fri, Jun 30, 2017 at 08:55:22PM -0700, Dan Williams wrote: >> >> ... >> >>> On Fri, Jun 30, 2017 at 9:09 AM, Jerry Hoemann wrote: >>> > + if (cmd == ND_CMD_CALL) >>> > + dsm_mask = nd_desc->bus_dsm_mask; >>> > desc = nd_cmd_bus_desc(cmd); >>> > uuid = to_nfit_uuid(NFIT_DEV_BUS); >>> > handle = adev->handle; >>> > @@ -1613,6 +1615,7 @@ static void acpi_nfit_init_dsms(struct acpi_nfit_desc *acpi_desc) >>> > struct nvdimm_bus_descriptor *nd_desc = &acpi_desc->nd_desc; >>> > const u8 *uuid = to_nfit_uuid(NFIT_DEV_BUS); >>> > struct acpi_device *adev; >>> > + unsigned long dsm_mask; >>> > int i; >>> > >>> > nd_desc->cmd_mask = acpi_desc->bus_cmd_force_en; >>> > @@ -1624,6 +1627,11 @@ static void acpi_nfit_init_dsms(struct acpi_nfit_desc *acpi_desc) >>> > if (acpi_check_dsm(adev->handle, uuid, 1, 1ULL << i)) >>> > set_bit(i, &nd_desc->cmd_mask); >>> > set_bit(ND_CMD_CALL, &nd_desc->cmd_mask); >>> > + >>> > + dsm_mask = 0x3bf; >>> >>> I went ahead and fixed this up to use dsm_mask defined like this: >>> >>> + dsm_mask = >>> + (1 << ND_CMD_ARS_CAP) | >>> + (1 << ND_CMD_ARS_START) | >>> + (1 << ND_CMD_ARS_STATUS) | >>> + (1 << ND_CMD_CLEAR_ERROR) | >>> + (1 << NFIT_CMD_TRANSLATE_SPA) | >>> + (1 << NFIT_CMD_ARS_INJECT_SET) | >>> + (1 << NFIT_CMD_ARS_INJECT_CLEAR) | >>> + (1 << NFIT_CMD_ARS_INJECT_GET); >>> >>> This drops function number 0 which userspace has no need to call. >> >> Actually I like to call function 0. Its an excellent test when >> modifying the code path as its a no side effects function whose output >> is known in advance and instantly recognizable. I also use it when >> testing new firmware. >> >> What is the downside to allowing it? What bad things happen? > > It allows implementations to bypass the standardization process and > ship new root DSMs. It's always possible to patch the kernel locally > for development, so I see no reason to ship this capability globally. Actually, just the discovery portion does not lead to this leak, but it's redundant when we have the 'dsm_mask' sysfs attribute.