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 D9E2F2209F; Mon, 19 Feb 2024 08:57:50 +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=1708333070; cv=none; b=AxJyO48IIi4SlaUn3biYosttVWQ/kopb/1zLsvD/oRBLn7W9diSIqsuJmF5Bcqq02imAvSeFAo80Gw1ZfDbfVmMxUXnnJyuSOm0gHYngTziAT/pDbGb6gYuhTZsKpr+7NiEknOCvOItTGz1m7XwURtsgLjXpAnp2kqqrAbNnKsc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708333070; c=relaxed/simple; bh=W5gz7RMXrw90JHSAorCY56w4sEZ+6vgfrsPlqOLhK3I=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=PDfWjqkd0rgdjLjuPku1Lr4Y0/hh73n+t1aG3ZgWiSN4xiasX9m+6TylF90HJaCwxk3Fy8O7V9rp3OzbueGg2BLxdUvaoplPsN/gFt0s6Svg7vPl6wBsqR8jUKIRsX8sMguC3ST/G/oHnHlBBa2AuPG3j7KFVJk14uACYCgOU4A= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=d+jMNdMU; 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="d+jMNdMU" Received: by smtp.kernel.org (Postfix) with ESMTPSA id EDB74C433F1; Mon, 19 Feb 2024 08:57:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708333070; bh=W5gz7RMXrw90JHSAorCY56w4sEZ+6vgfrsPlqOLhK3I=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=d+jMNdMUnY4SA9y3fIl2HfSZqdLHuiyL039fZrDWwOcm57cQj0gWGhkctiQaZBXeH JdaemzmMmW/jvNCcAJSB0v6cF01sb0fNU5KvCOLkBw0Y2ivV29dLarhm1K7WUmvADH +pyo3w6uq8l7BGYe+y8azIX9PwmU2DMk8MS5CKow= Date: Mon, 19 Feb 2024 09:57:47 +0100 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: <2024021910-paced-hazing-9c7a@gregkh> References: <170660662589.224441.11503798303914595072.stgit@dwillia2-xfh.jf.intel.com> <170660664848.224441.8152468052311375109.stgit@dwillia2-xfh.jf.intel.com> <2024013016-sank-idly-dd6b@gregkh> <65b9285a93e42_5cc6f294ac@dwillia2-mobl3.amr.corp.intel.com.notmuch> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <65b9285a93e42_5cc6f294ac@dwillia2-mobl3.amr.corp.intel.com.notmuch> On Tue, Jan 30, 2024 at 08:48:26AM -0800, Dan Williams wrote: > Greg KH wrote: > > 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 :) > > Pardon the spam, was just showing it in context of the patchset I was > developing. > > > 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? > > That works for me. Thanks Greg! I've applied this to my testing branch right now, and if 0-day passes everything (it's done so in other branches), I can create a static tag for everyone to pull from. thanks, greg k-h