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 56DE0C54EE9 for ; Wed, 28 Sep 2022 01:56:10 +0000 (UTC) Received: from h2850616.stratoserver.net (localhost [IPv6:::1]) by phobos.denx.de (Postfix) with ESMTP id 5126684CFE; Wed, 28 Sep 2022 03:55:36 +0200 (CEST) Authentication-Results: phobos.denx.de; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: phobos.denx.de; spf=pass smtp.mailfrom=u-boot-bounces@lists.denx.de Authentication-Results: phobos.denx.de; dkim=pass (1024-bit key; unprotected) header.d=chromium.org header.i=@chromium.org header.b="iPFiey/4"; dkim-atps=neutral Received: by phobos.denx.de (Postfix, from userid 109) id EBABE84BCD; Wed, 28 Sep 2022 03:55:15 +0200 (CEST) Received: from mail-wr1-x42b.google.com (mail-wr1-x42b.google.com [IPv6:2a00:1450:4864:20::42b]) (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 218A8803D2 for ; Wed, 28 Sep 2022 03:55:10 +0200 (CEST) Authentication-Results: phobos.denx.de; dmarc=pass (p=none dis=none) header.from=chromium.org Authentication-Results: phobos.denx.de; spf=pass smtp.mailfrom=sjg@google.com Received: by mail-wr1-x42b.google.com with SMTP id bq9so17550444wrb.4 for ; Tue, 27 Sep 2022 18:55:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date; bh=dwBCHqj2tzfG2jLezsc2eO5sntdfD9qYk+oC3QODzjQ=; b=iPFiey/4W9sP5Rx7RICFu5kTWS7wrORqIpWPbC7QJO81Cx33ZJoYljYavBZQlZIde8 /py4vYcuTjwcB/GNV0roySVQwXLX/npuDhVv5Ll9QFevNjxTn87wrr3s1zsUaNFvttoK /TfyOjb7yVNmf+OsYAIgES2siTUD9s3x62PYg= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=dwBCHqj2tzfG2jLezsc2eO5sntdfD9qYk+oC3QODzjQ=; b=kN3fvuCEaNmQ9SspGJglqhdaKpaemdl5X746MIm74VGFAzh17oLtO+UwPQOOAGicSJ 9GJ4QhCWF8w0O4wRHwWYsLUMyHBjgs4dLx0u2cHGGPhEjWD14WaL3FZ8kbQ+51nFg7co /9xHOWmarHJlUJxJIg0FVrz+Jnf8K42JVRVoq7mfPIzGe24GOjhhjGA0jqJmsJmqvfVe tmJXZTFQLX82CHIjthn61D36ax7+yt0VrSq267GKz0Zsg8/FL0TArfPvJ/hG/jS+ZhFX 21Vq2tC2qjg9UWCYULKs3rBVrTHSkESA5d6PGQL23CoaTZUVWMeig9h0K67ibOZ1o6bK 6cXw== X-Gm-Message-State: ACrzQf2CVnCywVDC9rR5+9NbPHAc32WVNs03tXSsvfxLq4fjUYbDZvKP tJI/nUtgyR6u0p2YuND8Gs+c3csFLwj17VEAUaXEcQ== X-Google-Smtp-Source: AMsMyM5zEP02FuVxZkALOYhYjKXECVT03PHpQDASTL6q4HG6YeJd1Hir0IgcPV6RhE0nsqsHtyUywVhrevEq+t4D188= X-Received: by 2002:a05:6000:1b03:b0:22a:7d12:db2b with SMTP id f3-20020a0560001b0300b0022a7d12db2bmr19001929wrz.268.1664330109305; Tue, 27 Sep 2022 18:55:09 -0700 (PDT) MIME-Version: 1.0 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> In-Reply-To: <422e5a00-b71e-2223-2d36-a856277d8415@canonical.com> From: Simon Glass Date: Tue, 27 Sep 2022 19:54:55 -0600 Message-ID: Subject: Re: [PATCH 0/2] efi_loader: provide media ID To: Heinrich Schuchardt Cc: AKASHI Takahiro , Ilias Apalodimas , Masahisa Kojima , U-Boot Mailing List Content-Type: text/plain; charset="UTF-8" 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 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? Regards, Simon