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 C99CCC433FE for ; Fri, 1 Apr 2022 07:42:52 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244090AbiDAHoj (ORCPT ); Fri, 1 Apr 2022 03:44:39 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36688 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S236779AbiDAHoi (ORCPT ); Fri, 1 Apr 2022 03:44:38 -0400 Received: from galois.linutronix.de (Galois.linutronix.de [IPv6:2a0a:51c0:0:12e:550::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 728D525ECAF; Fri, 1 Apr 2022 00:42:49 -0700 (PDT) Date: Fri, 1 Apr 2022 09:42:46 +0200 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020; t=1648798967; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=TrMSX3+gQilz8a7VNHdVxgsogGZEoAnFBXl8tPxCkps=; b=xRcTCcl+csECfBYuNeNbcoKWCk5bkTzdHZkh5H4ondpwyQ+mRfNAxVURLZ7BZMZ1nXodyz 0RdC+akthA17UUMCGhlJJGtTRKpueBs+Mv0k07cJ0OQyxrvgsPNrQZDxjKTzAbDXkK3O3k K/76cJx6ROrJi1G0DpVO/Qed01wyS1nCY/CNwBzsweCWieBVUi+jK6mJolTX4GWKFZmaJh xPBXvtjwjN4BOJPzegIWlxJ85o4ZDRJp6XnOG8IcMcERx1iHygjV9hYJ6uiRCBtQZ7TyPO mJ8wQzuIVRADijqlu6b8jOb0rZuUVe7njPkkt5K3wFpYzrgKpftD5QDE0NT4nA== DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=linutronix.de; s=2020e; t=1648798967; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=TrMSX3+gQilz8a7VNHdVxgsogGZEoAnFBXl8tPxCkps=; b=vntOswetkOSyBNw8nZmY0lvQccpo4n9jTQXXWNro3shzUqYzmw8U7y18KhVz7XtmsQ0jUP lu4mxX+xZNpxX9DA== From: Sebastian Andrzej Siewior To: Javier Martinez Canillas Cc: "Ahmed S. Darwish" , Ard Biesheuvel , Linux Kernel Mailing List , linux-efi , Brian Masney , Al Stone , Peter Robinson , Robbie Harwood , Peter Jones , Alexander Larsson , Andrew Halaney , linux-rt-users@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCH v2] efi: Allow to enable EFI runtime services by default on RT Message-ID: References: <20220331151654.184433-1-javierm@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-rt-users@vger.kernel.org On 2022-04-01 00:19:57 [+0200], Javier Martinez Canillas wrote: > > In case of (CONFIG_PREEMPT_RT=y && CONFIG_EFI_DISABLE_RUNTIME=n), > > shouldn't we add a small message in the kernel log warning that EFI > > runtime services are enabled for the RT kernel? > > > > In almost all HW, except custom ones with "verified" firmware, such a > > warning would be useful... This is especially true since in the embedded > > I considered that as well but was not sure about what that message should be. This makes sense and we had this in the past but dropped it for some reason. > Since it will be printed even on systems whose EFI firmwares do not > have such long call times as the ones described in the commit that > disabled the runtime services for RT. > > And in that case the warning may be misleading and make users believe > that a problem exists, which might not be accurate. Does this matter? The efi-rtc driver is known to cause latencies but it does not happen if the driver is not used. The same is probably true for efi-vars: It won't cause high latencies on _read_ but then a certain number of bit flips during read _may_ lead to write+erase which will cause higher latencies. Having a warning at boot (similar to trace_printk's warning) with the options listed that are known to case high latencies might be a help. There are some options that nobody will argue about like LOCKDEP. Then there are other like WATCHDOG or this one, where a debate might start ;) > Best regards, > Javier Sebastian