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 phobos.denx.de (phobos.denx.de [85.214.62.61]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 6E8EEC6FA82 for ; Wed, 28 Sep 2022 07:24:16 +0000 (UTC) Received: from h2850616.stratoserver.net (localhost [IPv6:::1]) by phobos.denx.de (Postfix) with ESMTP id 28DF784594; Wed, 28 Sep 2022 09:24:14 +0200 (CEST) Authentication-Results: phobos.denx.de; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: phobos.denx.de; spf=pass smtp.mailfrom=u-boot-bounces@lists.denx.de Authentication-Results: phobos.denx.de; dkim=pass (2048-bit key; unprotected) header.d=linaro.org header.i=@linaro.org header.b="QlziXzam"; dkim-atps=neutral Received: by phobos.denx.de (Postfix, from userid 109) id CABA28494B; Wed, 28 Sep 2022 09:24:12 +0200 (CEST) Received: from mail-pf1-x435.google.com (mail-pf1-x435.google.com [IPv6:2607:f8b0:4864:20::435]) (using TLSv1.3 with cipher TLS_AES_128_GCM_SHA256 (128/128 bits)) (No client certificate requested) by phobos.denx.de (Postfix) with ESMTPS id 6DECB8317B for ; Wed, 28 Sep 2022 09:24:09 +0200 (CEST) Authentication-Results: phobos.denx.de; dmarc=pass (p=none dis=none) header.from=linaro.org Authentication-Results: phobos.denx.de; spf=pass smtp.mailfrom=takahiro.akashi@linaro.org Received: by mail-pf1-x435.google.com with SMTP id 9so11747046pfz.12 for ; Wed, 28 Sep 2022 00:24:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linaro.org; s=google; h=in-reply-to:content-disposition:mime-version:references :mail-followup-to:message-id:subject:cc:to:from:date:from:to:cc :subject:date; bh=jmdpQqrVdlypAABRYY3QIQDkJ2FK/HwSr7VKKVp6T6I=; b=QlziXzamrFkaek7QtZp2Vm04P2mOLzLT/5ZvJqNYiU1tBy8M9dZvoSmhxlLwjGbdLZ Y0eOTJMFDPgHWNe+pExU/ildZp5SkUrLYQkn2+feaQw14GHh16su6gykEWSo/e9Ptbfb kwqwmzmnWCH/T7nIxEQfMeIW7PMd/6u4p00pQ+MiLPscXvA7MyaAwwZqWukPS0+kE84m YimgedtS3PuH9CxFdE+7lqPVaJ/yyO0NDM/4HjfGeTEuAlR8tmecaC1RA0eJGf3BYPd5 mBbGmb41tDjrUXSyCoc+KofGjdmWHq04ln/GuibSSaetB1Gao+9MZ+KWQIYZup/J8c+X r10Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=in-reply-to:content-disposition:mime-version:references :mail-followup-to:message-id:subject:cc:to:from:date :x-gm-message-state:from:to:cc:subject:date; bh=jmdpQqrVdlypAABRYY3QIQDkJ2FK/HwSr7VKKVp6T6I=; b=Ypl/gmH2uHEI4O3o23zE+WlFkom8R8CeenuAZ8vOdL6YB0lYIsygIpXYGT8ixFuLy5 u4jn+1+MFbi69Bp0xTv80smCLQ7MlP6fb9yB4Iy7NgoKBvYIRhNWRAEm/vYic1l8aEYD VYmNeThSI8XbUbgqGcUjvBpNjlyWdEKuFnAj+OmTtq8q4yIasYkEi9FNDVJJ0A9dhOxJ MkwJzrJp6Oz+29o4ILrSQbY6WNo1FHOVOUOfEB2Du/15XU9xFoqtI+ZAFcf0IZFcLh7N pffDPA9QNxI9iotOCQD0crPvfhUjOUxflvpcw8N4mWuHDtMDSptaemehXjcOr5hpKnOV fnsg== X-Gm-Message-State: ACrzQf3+pGp5t2RsCm0gRiX3tAI0OxWvTYUyLzZ4xyYpgFeMdEkIArBz rBADjaxBP12pVNjr6TbU1xhMwg== X-Google-Smtp-Source: AMsMyM5LP7ceQbvkYJi0HyfQkCsVVfLbnmAXwqLj/YsXpQoz+Fjagd0fGi5QiNuSyITUMfDquSsyWQ== X-Received: by 2002:a63:db4a:0:b0:43c:9d3b:9c4a with SMTP id x10-20020a63db4a000000b0043c9d3b9c4amr16376374pgi.474.1664349847623; Wed, 28 Sep 2022 00:24:07 -0700 (PDT) Received: from laputa ([2400:4050:c3e1:100:3e1:208a:af57:a9c8]) by smtp.gmail.com with ESMTPSA id l2-20020a170902f68200b001788ccecbf5sm2954406plg.31.2022.09.28.00.24.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 28 Sep 2022 00:24:06 -0700 (PDT) Date: Wed, 28 Sep 2022 16:24:03 +0900 From: AKASHI Takahiro To: Heinrich Schuchardt Cc: Simon Glass , Ilias Apalodimas , Masahisa Kojima , U-Boot Mailing List Subject: Re: [PATCH 0/2] efi_loader: provide media ID Message-ID: <20220928072403.GC57805@laputa> Mail-Followup-To: AKASHI Takahiro , Heinrich Schuchardt , Simon Glass , Ilias Apalodimas , Masahisa Kojima , U-Boot Mailing List References: <20220915200242.18358-1-heinrich.schuchardt@canonical.com> <20220916005805.GA45676@laputa> <933e5bf9-1eef-3e8b-c55d-dad943f9177f@canonical.com> <20220927015117.GA34139@laputa> <422e5a00-b71e-2223-2d36-a856277d8415@canonical.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-BeenThere: u-boot@lists.denx.de X-Mailman-Version: 2.1.39 Precedence: list List-Id: U-Boot discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: u-boot-bounces@lists.denx.de Sender: "U-Boot" X-Virus-Scanned: clamav-milter 0.103.6 at phobos.denx.de X-Virus-Status: Clean On Wed, Sep 28, 2022 at 08:57:43AM +0200, Heinrich Schuchardt wrote: > > > On 9/28/22 03:54, Simon Glass wrote: > > Hi, > > > > On Tue, 27 Sept 2022 at 00:53, Heinrich Schuchardt > > wrote: > > > > > > > > > > > > On 9/27/22 03:51, AKASHI Takahiro wrote: > > > > On Mon, Sep 26, 2022 at 08:06:52AM +0200, Heinrich Schuchardt wrote: > > > > > > > > > > > > > > > On 9/16/22 02:58, AKASHI Takahiro wrote: > > > > > > On Thu, Sep 15, 2022 at 10:02:40PM +0200, Heinrich Schuchardt wrote: > > > > > > > The medium a device like 'mmc 0' or 'usb 0' points to may change over > > > > > > > time. Hence device type and number are not sufficient to identify the > > > > > > > inserted medium. The same is true for the device path generated for > > > > > > > such a device. > > > > > > > > > > > > Well, it depends on how a device path is generated in U-Boot's UEFI > > > > > > implementation. I believe that a device path represents an "unique path" > > > > > > to a given device however this device is enumerated. > > > > > > In this sense, the current dp_fill()/efi_dp_from_part() is not a right > > > > > > implementation as it relies on device numbers. > > > > > > Furthermore, a generated device path here is different from one generated > > > > > > by EDK2 (even if both software are run on the same board). > > > > > > > > > > > > This is an issue that I used to tackle in > > > > > > https://lists.denx.de/pipermail/u-boot/2021-November/468216.html > > > > > > although I have since had no progress. > > > > > > > > > > > > > This is why the EFI_BLOCK_IO_PROTOCOL provides a field > > > > > > > MediaId. > > > > > > > > > > > > > > Whenever a removable medium is changed or a new block device with a > > > > > > > previously used device path is created we should provide a different > > > > > > > MediaID. > > > > > > > > > > > > > > This series adds a field media_id to the block device descriptor and fills > > > > > > > it after probing. The value of the field is then copied to the > > > > > > > EFI_BLOCK_IO_PROTOCOL. > > > > > > > > > > > > I'm afraid that your patch doesn't always work as you expect. > > > > > > When "scsi rescan" or "usb stop; usb start", for instance, is invoked, > > > > > > all the existing devices and associated blk_desc structures are once freed > > > > > > and even if nothing is changed, i.e. a device is neither removed nor added, > > > > > > the exact same structures will be re-created. > > > > > > With your patch applied, however, a new (and different) "media_id" will be > > > > > > assigned to an existing device. UEFI User may be notified of "media change". > > > > > > (To be honest, this is quite unlikely because the current UEFI implementation > > > > > > doesn't use BLOCK_IO_PROTOCOL internally, say, for file system access.) > > > > > > > > > > This behavior matches what EDK II does if you remove a device and create a > > > > > new device. > > > > > > > > I don't think that EDK2 has "scsi rescan" or others, which users can invoke > > > > at any time. Moreover, I believe that EDK2 code (drivers) checks whether a device > > > > is really changed or not before updating a MediaId. > > > > > > > > > If a device is removed and recreated anything could have happened in between > > > > > like complete repartitioning. We cannot assume that any cached state is > > > > > valid anymore even if GUIDs are the same. > > > > > > > > I'm not sure if you fully understand my point. > > > > My assumption is the case where a device is NOT removed around "scsi rescan" > > > > (or usb stop/start) and stays online. In this case, > > > > 1. access to, say, "scsi 0:1", via UEFI BLOCK_IO succeeds > > > > 2. "scsi rescan" > > > > 3. access to the same device, "scsi 0:1", via UEFI BLOCK_IO > > > > currently (3) succeeds, but with your patch, it may potentially fail because > > > > of media_id altered. > > > > > > > > I admit that it will not happen under the current UEFI implementation because > > > > non of UEFI applications will survive across command lines and none of information, > > > > including media_id or handle, can be carried over from (1) to (3). > > > > But unconditionally incrementing an internally-held media_id, as in your patch, > > > > is a wrong behavior. > > > > > > The patch issues a new media ID if a new device is probed which only > > > happens to have the same device number if another device of that number > > > was removed before. > > > > > > Commands like 'usb scan' don't necessarily issue the same numbers to the > > > same device as before the command if a new device has been attached in > > > the meanwhile. > > > > > > Assuming that a new device contains the same medium as an old one > > > because by chance it has the same device number is definitively unsafe. > > > > > > If a device is probed, we have to assume that it contains a new medium. > > > > Sorry if I repeat myself, but this sort of thing should be handled in > > the driver model code. Can we get some more progress on integrating > > the EFI layer better? > > The last mails where about *whether* the media ID should be bumped after a > block device has been created and not about where we will implement it. Indeed. I don't care "where" for now, but "how" or "whether". The most essential issue is that none of U-Boot block device drivers has ability of detecting media insertion or removal immediately (due to the lack of interrupt support). This is even not related to DM or not. -Takahiro Akashi > Best regards > > Heinrich