From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755951AbeCHOIq (ORCPT ); Thu, 8 Mar 2018 09:08:46 -0500 Received: from mail.skyhub.de ([5.9.137.197]:34942 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755027AbeCHOIo (ORCPT ); Thu, 8 Mar 2018 09:08:44 -0500 Date: Thu, 8 Mar 2018 15:08:31 +0100 From: Borislav Petkov To: "Prakhya, Sai Praneeth" Cc: "linux-efi@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Chun-Yi Lee , "Luck, Tony" , Will Deacon , "Hansen, Dave" , Mark Rutland , Bhupesh Sharma , "Neri, Ricardo" , "Shankar, Ravi V" , Matt Fleming , "Zijlstra, Peter" , Ard Biesheuvel , "Williams, Dan J" Subject: Re: [PATCH V2 2/3] efi: Introduce efi_rts_workqueue and some infrastructure to invoke all efi_runtime_services() Message-ID: <20180308140830.GE21166@pd.tnic> References: <1520292190-5027-1-git-send-email-sai.praneeth.prakhya@intel.com> <1520292190-5027-3-git-send-email-sai.praneeth.prakhya@intel.com> <20180307121047.GG23662@pd.tnic> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.9.3 (2018-01-21) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Mar 08, 2018 at 05:31:03AM +0000, Prakhya, Sai Praneeth wrote: > Another warning by checkpatch is "use of in_atomic() in drivers code" I'm assuming it warns because you're touching files in drivers/ but the efi fun is not really a driver... But looking at patch 3, that thing looks like a real mess. Some of the things - pstore, it seems - do stuff in atomic context and yet you want to do efi stuff in a workqueue which doesn't stomach atomic context to begin with. So if you wanna do workqueue, you should make sure all efi stuff gets delayed to process context and queued properly. For example, we log MCEs from atomic context by putting them on a lockless buffer and then kicking irq_work to queue the work when we return to process context. Can you do something like that? "Hence, pstore calls efi_runtime_services() without using efi_rts_wq" - that doesn't sound like optimal design to me. I would try to shove them all through the workqueue - not have exceptions. Then this: > A potential issue could be, for instance, an NMI interrupt (like perf) > trying to profile some user data while in efi_pgd. I can't understand. How did we handle this until now and why is it a problem all of a sudden? Because I don't recall being unable to run perf while efi runtime services are happening. -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.