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[23.128.96.37]) by mx.google.com with ESMTPS id h24-20020a17090aa89800b0027ced9acac0si11052721pjq.2.2023.10.24.06.21.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 24 Oct 2023 06:21:31 -0700 (PDT) Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) client-ip=23.128.96.37; Authentication-Results: mx.google.com; dkim=pass header.i=@linutronix.de header.s=2020 header.b=ZJVq0c9E; dkim=neutral (no key) header.i=@linutronix.de header.s=2020e header.b="f/qj2GnE"; spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.37 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=pass (p=NONE sp=QUARANTINE dis=NONE) header.from=linutronix.de Received: from out1.vger.email (depot.vger.email [IPv6:2620:137:e000::3:0]) by snail.vger.email (Postfix) with ESMTP id 8880A802C8CB; Tue, 24 Oct 2023 06:21:30 -0700 (PDT) X-Virus-Status: Clean X-Virus-Scanned: clamav-milter 0.103.10 at snail.vger.email Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234500AbjJXNVU (ORCPT + 26 others); Tue, 24 Oct 2023 09:21:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44176 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234484AbjJXNUz (ORCPT ); Tue, 24 Oct 2023 09:20:55 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DE5DE10E5; Tue, 24 Oct 2023 06:20:50 -0700 (PDT) Date: Tue, 24 Oct 2023 13:20:48 -0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1698153649; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=T/33YqcWY5VD1riO4uCxfHce6JOJnAKqF5C2JA5Vw18=; b=ZJVq0c9EZDvcaMHSUU/c1+WLr0mN7MaVDwEwTCXMmkAnRZHBc+JPlqhvRjim2bf/XDJZG3 uu6ElCKsQ2bbAeAkIoFOHYyr/bcJG3ZTZFvKJwT3TvQT15k7XP842mvKtVOnEllFChPLY1 AUeToqs5Sn97XfgQKwGOUh/txGmyA6mrQwVT8aVC9DuKMyiHS3dOjmuIyfV8bM7gEZ7vDE dN6c9IaMP2EpppBp267QzPZPW+h/inI7CNMN7CzbiVlrJCqtuVX5ldbESMa5op8iqziLQh ZA44vCNIVey2yNEok1r5VE3YWm/sT2KnRZmmSVeKsNkjJRbwzinYLSfofrhsjQ== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1698153649; h=from:from:sender:sender:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=T/33YqcWY5VD1riO4uCxfHce6JOJnAKqF5C2JA5Vw18=; b=f/qj2GnEYhXS9VZK2fajSt+Fy2vkoNaqCaDABUaks1mLmJe8DsMAbnOEjOgQKODcliqAjd 2gcGbeDk6PXvUFAg== From: "tip-bot2 for Thomas Gleixner" Sender: tip-bot2@linutronix.de Reply-to: linux-kernel@vger.kernel.org To: linux-tip-commits@vger.kernel.org Subject: [tip: x86/microcode] x86/microcode: Prepare for minimal revision check Cc: Thomas Gleixner , "Borislav Petkov (AMD)" , x86@kernel.org, linux-kernel@vger.kernel.org In-Reply-To: <20231017211724.079611170@linutronix.de> References: <20231017211724.079611170@linutronix.de> MIME-Version: 1.0 Message-ID: <169815364859.3135.1392271485663377022.tip-bot2@tip-bot2> Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails X-Spam-Status: No, score=-4.4 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_MED,SPF_HELO_NONE, SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-Greylist: Sender passed SPF test, not delayed by milter-greylist-4.6.4 (snail.vger.email [0.0.0.0]); Tue, 24 Oct 2023 06:21:30 -0700 (PDT) X-getmail-retrieved-from-mailbox: INBOX X-GMAIL-THRID: 1780039595682541456 X-GMAIL-MSGID: 1780643204877640099 The following commit has been merged into the x86/microcode branch of tip: Commit-ID: 9407bda845dd19756e276d4f3abc15a20777ba45 Gitweb: https://git.kernel.org/tip/9407bda845dd19756e276d4f3abc15a20777ba45 Author: Thomas Gleixner AuthorDate: Tue, 17 Oct 2023 23:24:16 +02:00 Committer: Borislav Petkov (AMD) CommitterDate: Tue, 24 Oct 2023 15:05:55 +02:00 x86/microcode: Prepare for minimal revision check Applying microcode late can be fatal for the running kernel when the update changes functionality which is in use already in a non-compatible way, e.g. by removing a CPUID bit. There is no way for admins which do not have access to the vendors deep technical support to decide whether late loading of such a microcode is safe or not. Intel has added a new field to the microcode header which tells the minimal microcode revision which is required to be active in the CPU in order to be safe. Provide infrastructure for handling this in the core code and a command line switch which allows to enforce it. If the update is considered safe the kernel is not tainted and the annoying warning message not emitted. If it's enforced and the currently loaded microcode revision is not safe for late loading then the load is aborted. Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Link: https://lore.kernel.org/r/20231017211724.079611170@linutronix.de --- Documentation/admin-guide/kernel-parameters.txt | 5 +++- arch/x86/Kconfig | 23 +++++++++++++++- arch/x86/kernel/cpu/microcode/amd.c | 3 ++- arch/x86/kernel/cpu/microcode/core.c | 19 +++++++++---- arch/x86/kernel/cpu/microcode/intel.c | 3 ++- arch/x86/kernel/cpu/microcode/internal.h | 2 +- 6 files changed, 49 insertions(+), 6 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 0a1731a..d762e17 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -3275,6 +3275,11 @@ mga= [HW,DRM] + microcode.force_minrev= [X86] + Format: + Enable or disable the microcode minimal revision + enforcement for the runtime microcode loader. + min_addr=nn[KMG] [KNL,BOOT,IA-64] All physical memory below this physical address is ignored. diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index db75120..cadea3f 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -1326,7 +1326,28 @@ config MICROCODE_LATE_LOADING is a tricky business and should be avoided if possible. Just the sequence of synchronizing all cores and SMT threads is one fragile dance which does not guarantee that cores might not softlock after the loading. Therefore, - use this at your own risk. Late loading taints the kernel too. + use this at your own risk. Late loading taints the kernel unless the + microcode header indicates that it is safe for late loading via the + minimal revision check. This minimal revision check can be enforced on + the kernel command line with "microcode.minrev=Y". + +config MICROCODE_LATE_FORCE_MINREV + bool "Enforce late microcode loading minimal revision check" + default n + depends on MICROCODE_LATE_LOADING + help + To prevent that users load microcode late which modifies already + in use features, newer microcode patches have a minimum revision field + in the microcode header, which tells the kernel which minimum + revision must be active in the CPU to safely load that new microcode + late into the running system. If disabled the check will not + be enforced but the kernel will be tainted when the minimal + revision check fails. + + This minimal revision check can also be controlled via the + "microcode.minrev" parameter on the kernel command line. + + If unsure say Y. config X86_MSR tristate "/dev/cpu/*/msr - Model-specific register support" diff --git a/arch/x86/kernel/cpu/microcode/amd.c b/arch/x86/kernel/cpu/microcode/amd.c index 102aebc..9373ec0 100644 --- a/arch/x86/kernel/cpu/microcode/amd.c +++ b/arch/x86/kernel/cpu/microcode/amd.c @@ -888,6 +888,9 @@ static enum ucode_state request_microcode_amd(int cpu, struct device *device) enum ucode_state ret = UCODE_NFOUND; const struct firmware *fw; + if (force_minrev) + return UCODE_NFOUND; + if (c->x86 >= 0x15) snprintf(fw_name, sizeof(fw_name), "amd-ucode/microcode_amd_fam%.2xh.bin", c->x86); diff --git a/arch/x86/kernel/cpu/microcode/core.c b/arch/x86/kernel/cpu/microcode/core.c index 718d648..666d25b 100644 --- a/arch/x86/kernel/cpu/microcode/core.c +++ b/arch/x86/kernel/cpu/microcode/core.c @@ -46,6 +46,9 @@ static struct microcode_ops *microcode_ops; bool dis_ucode_ldr = true; +bool force_minrev = IS_ENABLED(CONFIG_MICROCODE_LATE_FORCE_MINREV); +module_param(force_minrev, bool, S_IRUSR | S_IWUSR); + /* * Synchronization. * @@ -531,15 +534,17 @@ static int load_cpus_stopped(void *unused) return 0; } -static int load_late_stop_cpus(void) +static int load_late_stop_cpus(bool is_safe) { unsigned int cpu, updated = 0, failed = 0, timedout = 0, siblings = 0; unsigned int nr_offl, offline = 0; int old_rev = boot_cpu_data.microcode; struct cpuinfo_x86 prev_info; - pr_err("Attempting late microcode loading - it is dangerous and taints the kernel.\n"); - pr_err("You should switch to early loading, if possible.\n"); + if (!is_safe) { + pr_err("Late microcode loading without minimal revision check.\n"); + pr_err("You should switch to early loading, if possible.\n"); + } atomic_set(&late_cpus_in, num_online_cpus()); atomic_set(&offline_in_nmi, 0); @@ -589,7 +594,9 @@ static int load_late_stop_cpus(void) return -EIO; } - add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK); + if (!is_safe || failed || timedout) + add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK); + pr_info("load: updated on %u primary CPUs with %u siblings\n", updated, siblings); if (failed || timedout) { pr_err("load incomplete. %u CPUs timed out or failed\n", @@ -679,7 +686,9 @@ static int load_late_locked(void) switch (microcode_ops->request_microcode_fw(0, µcode_pdev->dev)) { case UCODE_NEW: - return load_late_stop_cpus(); + return load_late_stop_cpus(false); + case UCODE_NEW_SAFE: + return load_late_stop_cpus(true); case UCODE_NFOUND: return -ENOENT; default: diff --git a/arch/x86/kernel/cpu/microcode/intel.c b/arch/x86/kernel/cpu/microcode/intel.c index 905ed3b..14aa4c6 100644 --- a/arch/x86/kernel/cpu/microcode/intel.c +++ b/arch/x86/kernel/cpu/microcode/intel.c @@ -480,6 +480,9 @@ static enum ucode_state parse_microcode_blobs(int cpu, struct iov_iter *iter) unsigned int curr_mc_size = 0; u8 *new_mc = NULL, *mc = NULL; + if (force_minrev) + return UCODE_NFOUND; + while (iov_iter_count(iter)) { struct microcode_header_intel mc_header; unsigned int mc_size, data_size; diff --git a/arch/x86/kernel/cpu/microcode/internal.h b/arch/x86/kernel/cpu/microcode/internal.h index 1a396fc..f8047b1 100644 --- a/arch/x86/kernel/cpu/microcode/internal.h +++ b/arch/x86/kernel/cpu/microcode/internal.h @@ -13,6 +13,7 @@ struct device; enum ucode_state { UCODE_OK = 0, UCODE_NEW, + UCODE_NEW_SAFE, UCODE_UPDATED, UCODE_NFOUND, UCODE_ERROR, @@ -88,6 +89,7 @@ static inline unsigned int x86_cpuid_family(void) } extern bool dis_ucode_ldr; +extern bool force_minrev; #ifdef CONFIG_CPU_SUP_AMD void load_ucode_amd_bsp(unsigned int family);