From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E8F5E8612C; Tue, 30 Jan 2024 16:44:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706633046; cv=none; b=cLXjpcX0Xej2T8NeumuJi1KjULIsi+t2E2cHPuzMQ0sZZCxZh/C1Mz7KYFyr5J1Kwi8ksKQbo9oFsQtehELtIm/N39LoCjjOXoMWSnpYtQCDKUZhNXVeFg+fP2ZYlb8lZwBC28wOhMI/9ZJNwb12CE0hvJLQgSwKlzopVyv/W+4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706633046; c=relaxed/simple; bh=QgABafDNsktgkXRudOCLlwXhcYXw4Ycvqs7d0i/LQ1U=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XcbUSyMx655xevO71/iiR6rWZQQVmpIi7aZCmKXB+2pDPedW0GY/3oUdA5N/HM7vB1kcH88swf4WlAv72BO5ZXtZqc/BXpDgoQpmYjVLVLgUcHlR0NkMa/qsTocjczk+0gqJ5HTJSAqTMMW6IQM1vKm4Y45AlXIPxD/Ot87CDyE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=uzqAZKLn; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="uzqAZKLn" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7ADF1C433F1; Tue, 30 Jan 2024 16:44:05 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1706633045; bh=QgABafDNsktgkXRudOCLlwXhcYXw4Ycvqs7d0i/LQ1U=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=uzqAZKLnLfqAX16wTaHfxzIhJle9n1YAO75dG0h3i7HfVla1jerWbReyXqYPut88f Y0Lft1wcBTSuVpW2zVmxysZP8URMLHnmB5qI8n9dmNgfb7keXFOZTJh6ncc3YYSouz KOofi6pqU7s2S/17CPUT1SNuEz0vb8M/cZYNJEAI= Date: Tue, 30 Jan 2024 08:44:04 -0800 From: Greg KH To: Dan Williams Cc: linux-coco@lists.linux.dev, linux-pci@vger.kernel.org Subject: Re: [RFC PATCH 4/5] sysfs: Introduce a mechanism to hide static attribute_groups Message-ID: <2024013016-sank-idly-dd6b@gregkh> References: <170660662589.224441.11503798303914595072.stgit@dwillia2-xfh.jf.intel.com> <170660664848.224441.8152468052311375109.stgit@dwillia2-xfh.jf.intel.com> Precedence: bulk X-Mailing-List: linux-pci@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <170660664848.224441.8152468052311375109.stgit@dwillia2-xfh.jf.intel.com> On Tue, Jan 30, 2024 at 01:24:08AM -0800, Dan Williams wrote: > Add a mechanism for named attribute_groups to hide their directory at > sysfs_update_group() time, or otherwise skip emitting the group > directory when the group is first registered. It piggybacks on > is_visible() in a similar manner as SYSFS_PREALLOC, i.e. special flags > in the upper bits of the returned mode. To use it, specify a symbol > prefix to DEFINE_SYSFS_GROUP_VISIBLE(), and then pass that same prefix > to SYSFS_GROUP_VISIBLE() when assigning the @is_visible() callback: > > DEFINE_SYSFS_GROUP_VISIBLE($prefix) > > struct attribute_group $prefix_group = { > .name = $name, > .is_visible = SYSFS_GROUP_VISIBLE($prefix), > }; > > SYSFS_GROUP_VISIBLE() expects a definition of $prefix_group_visible() > and $prefix_attr_visible(), where $prefix_group_visible() just returns > true / false and $prefix_attr_visible() behaves as normal. > > The motivation for this capability is to centralize PCI device > authentication in the PCI core with a named sysfs group while keeping > that group hidden for devices and platforms that do not meet the > requirements. In a PCI topology, most devices will not support > authentication, a small subset will support just PCI CMA (Component > Measurement and Authentication), a smaller subset will support PCI CMA + > PCIe IDE (Link Integrity and Encryption), and only next generation > server hosts will start to include a platform TSM (TEE Security > Manager). > > Without this capability the alternatives are: > > * Check if all attributes are invisible and if so, hide the directory. > Beyond trouble getting this to work [1], this is an ABI change for > scenarios if userspace happens to depend on group visibility absent any > attributes. I.e. this new capability avoids regression since it does > not retroactively apply to existing cases. > > * Publish an empty /sys/bus/pci/devices/$pdev/tsm/ directory for all PCI > devices (i.e. for the case when TSM platform support is present, but > device support is absent). Unfortunate that this will be a vestigial > empty directory in the vast majority of cases. > > * Reintroduce usage of runtime calls to sysfs_{create,remove}_group() > in the PCI core. Bjorn has already indicated that he does not want to > see any growth of pci_sysfs_init() [2]. > > * Drop the named group and simulate a directory by prefixing all > TSM-related attributes with "tsm_". Unfortunate to not use the naming > capability of a sysfs group as intended. > > In comparison, there is a small potential for regression if for some > reason an @is_visible() callback had dependencies on how many times it > was called. Additionally, it is no longer an error to update a group > that does not have its directory already present, and it is no longer a > WARN() to remove a group that was never visible. > > Link: https://lore.kernel.org/all/2024012321-envious-procedure-4a58@gregkh/ [1] > Link: https://lore.kernel.org/linux-pci/20231019200110.GA1410324@bhelgaas/ [2] > Signed-off-by: Dan Williams > --- > fs/sysfs/group.c | 45 ++++++++++++++++++++++++++++------- > include/linux/sysfs.h | 63 ++++++++++++++++++++++++++++++++++++++++--------- > 2 files changed, 87 insertions(+), 21 deletions(-) You beat me to this again :) I have tested this patch, and it looks good, I'll send out my series that uses it for a different subsystem as well. I guess I can take this as a static tag for others to pull from for this rc development cycle? thanks, greg k-h