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 X-Spam-Level: X-Spam-Status: No, score=-2.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3DDF3C433DB for ; Thu, 18 Mar 2021 17:45:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E5FD264F10 for ; Thu, 18 Mar 2021 17:45:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231847AbhCRRoc (ORCPT ); Thu, 18 Mar 2021 13:44:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40860 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230409AbhCRRo3 (ORCPT ); Thu, 18 Mar 2021 13:44:29 -0400 Received: from mail-pl1-x62a.google.com (mail-pl1-x62a.google.com [IPv6:2607:f8b0:4864:20::62a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 752EFC06175F; Thu, 18 Mar 2021 10:44:29 -0700 (PDT) Received: by mail-pl1-x62a.google.com with SMTP id k4so1668609plk.5; Thu, 18 Mar 2021 10:44:29 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=silYB0ReWesGT2gy/SuDL9rDUPXG+HkXO/MQkv5g2jM=; b=YxJy+2UgFvhSJ5sTGc0AonW0IZ31y/JHYc5PyZwE49qDmVAEEQ9+U/DGwEZ6jcM9fT d0wM0A4wLR82s+Dj4vfSKOnU65Aq3EU+Mx5lkuFMTye1/4jwFGr1vKqGYHZf+NDhO/ii ToUw1j51g717tBLanTwR6ESRQXPnNd5aw6Qsqyphail9J2gKNh5vEg2lTCT69KYh96Cs fppNOCZ0ZUHrtfq16NQsTtEIVfXEQ7YcZAMNidIeKniAARkWn/Jhet3dNZqFbekIqRk4 NvlkXdcgRSkM/tJJMkUlB0PN5sT60k+Y2dJUL7KhJpoCHn5ahOwpQ88RzhVDJC/2aX5m 5WnA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=silYB0ReWesGT2gy/SuDL9rDUPXG+HkXO/MQkv5g2jM=; b=GseHYUTUTUUunao6GYgjL6zUCZ0NCp9/hhpQDTklMQGWWWvXlAfIZMk+Yo0od7vlSb E9J63PmYM7WN0IBPKghC5FX7zYi4C++brYXX1FAVNBDy68LI3LJsDeqGUFGmm0EmxhYZ 0evGa7W1hcwza934FeTYNSNh0ouiUOSv5ihTFNcPvabu/RS8k3SmIMvk0SnThlEv1umQ NdIAPBrv+NZ/95F8wZ2UtGDwj07dS75kifjeZTBNTPNmWYTAKxWTZrrF5ATZ86voGMUa gb+WHawYvYMnleRFi96ezdjciGs7PLm/1XY8yKWrs54HW7i8fGhA6YMPcUkUrwZRT0pF 4yFQ== X-Gm-Message-State: AOAM531ICYYEcbc5fC1cJhHTgu6PrKmryW/Edmqe0YJMyww3b4U+P5wb EtweXS76nKBjOl2x3qz3c3s= X-Google-Smtp-Source: ABdhPJxuSldlAiWbBW+PuJ6B4npIGUgS2l3D+DC6H4/WS6Uxgd7pNyalUYjxERzIB65Y7cuWxdD90w== X-Received: by 2002:a17:90b:100a:: with SMTP id gm10mr5487372pjb.0.1616089468752; Thu, 18 Mar 2021 10:44:28 -0700 (PDT) Received: from localhost ([103.248.31.158]) by smtp.gmail.com with ESMTPSA id w22sm2884164pfi.133.2021.03.18.10.44.27 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Mar 2021 10:44:28 -0700 (PDT) Date: Thu, 18 Mar 2021 23:13:44 +0530 From: Amey Narkhede To: Leon Romanovsky Cc: raphael.norwitz@nutanix.com, linux-pci@vger.kernel.org, bhelgaas@google.com, linux-kernel@vger.kernel.org, alay.shah@nutanix.com, suresh.gumpula@nutanix.com, shyam.rajendran@nutanix.com, felipe@nutanix.com, alex.williamson@redhat.com Subject: Re: [PATCH 4/4] PCI/sysfs: Allow userspace to query and set device reset mechanism Message-ID: <20210318174344.yslqpfyct6ziwypd@archlinux> References: <20210317112309.nborigwfd26px2mj@archlinux> <20210317131718.3uz7zxnvoofpunng@archlinux> <20210317113140.3de56d6c@omen.home.shazbot.org> <20210318142252.fqi3das3mtct4yje@archlinux> <20210318170143.ustrbjaqdl644ozj@archlinux> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On 21/03/18 07:35PM, Leon Romanovsky wrote: > On Thu, Mar 18, 2021 at 10:31:43PM +0530, Amey Narkhede wrote: > > On 21/03/18 04:57PM, Leon Romanovsky wrote: > > > On Thu, Mar 18, 2021 at 07:52:52PM +0530, Amey Narkhede wrote: > > > > On 21/03/18 11:09AM, Leon Romanovsky wrote: > > > > > On Wed, Mar 17, 2021 at 11:31:40AM -0600, Alex Williamson wrote: > > > > > > On Wed, 17 Mar 2021 15:58:40 +0200 > > > > > > Leon Romanovsky wrote: > > <...> > > > > > > I'm lost here, does vfio-pci use sysfs interface or internal to the kernel API? > > > > > > > > > > If it is latter then we don't really need sysfs, if not, we still need > > > > > some sort of DB to create second policy, because "supported != working". > > > > > What am I missing? > > > > > > > > > > Thanks > > > > > > > > > Can you explain bit more about why supported != working? > > > > > > It is written in the commit message of this patch. > > > https://lore.kernel.org/lkml/20210312173452.3855-1-ameynarkhede03@gmail.com/ > > > "This feature aims to allow greater control of a device for use cases > > > as device assignment, where specific device or platform issues may > > > interact poorly with a given reset method, and for which device specific > > > quirks have not been developed." > > > > > > You wrote it and also repeated it a couple of times during the discussion. > > > > > > If device can understand that specific reset doesn't work, it won't > > > perform it in first place. > > > > > > Thanks > > Is it possible for device to understand whether or not specific reset > > will work or not prior to performing reset and after it indicates > > support for that reset method? Maybe theres problem with that particular > > piece of hardware in that machine. > > How can database be maintained if a particular machines have > > particular piece of faulty HW? > > It was exactly the reason why I think that VM usecase presented by > you is not viable. > Well I didn't present it as new use case. I just gave existing usecase based on existing reset attribute. Nothing new here. Nothing really changes wrt that use case. > > If for some reason reset doesn't work it will just give -ENOTTY. > > This isn't any different from existing behavior.Actually it informs user > > that the reset method didn't reset the device and user can use different > > reset method instead of implicitly using different reset method. > > If user doesn't explicitly set preferred reset method then > > we go ahead with existing implicit fall through behavior which will try all > > available reset methods until any one of them works. > > If you have device that doesn't support reset at all then you have > > option to completely disable it unlike existing reset attribute where > > you cannot disable reset. So it gives greater control where you can > > disable the reset altogether when quirk isn't developed yet. > > I explicitly asked to hear usecase, right now, I got an explanation from > Alex for policy decision (which doesn't need sysfs) and from you about > overcoming HW bugs with expectation that user will be guru of PCI reset > methods. > > > > > We can't expect to develop quirk for every device in existence. > > It doesn't give us an excuse do not try. > > > For example on my laptop elantech touchpad still doesn't work in 2021 > > with vanilla kernel, arch linux applies the patch which was reverted in > > mainline kernel for some reason. > > I see it as a good example of cheap solution. Vendor won't fix your > touchpad because distros provide workaround. The same will be with reset. > > Thanks > As mentioned earlier not all vendors care about Linux and not all of the population can afford to buy new HW just to run Linux. Thanks, Amey