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 2C1831F429C; Mon, 16 Jun 2025 21:05:31 +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=1750107933; cv=none; b=leHiinfxTGWHuXW2bbwaEK8jq87lRtcO3rC1vHtVJA8YzNCnVFQQphWzOt3k9OJrhtWCud/NSxy86NIjspROcOGDnyyneqSG/B3iJNfJNhDEwzGBxBbz8Tu94vlY9gG+zBqOETyBHHGonA149rFaKgqnKl3eLAn/a563tul5Is4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750107933; c=relaxed/simple; bh=0W3oaKucpq4l/BVEw8nroG4LqtFe0etV3ZPi0IaCQ2U=; h=Date:From:To:Cc:Subject:Message-ID:MIME-Version:Content-Type: Content-Disposition:In-Reply-To; b=XGxc4lAY4WcqmF13o3O0iUcYRKze477lKRW3H00JdwWRR8JIjWRXECga+UQgkFqn0rCIVDwNHCQKf9OyAxM0jd6ka9+U+spDo6YOEXwJIE8BlZfVCW7WEU+vkq3S0SUpDgD9J4sVgWxFISt3qDDagX7TIpPz5TSwfoyN9exgqzQ= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=UL/gkN/S; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="UL/gkN/S" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 7A9B0C4CEEA; Mon, 16 Jun 2025 21:05:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1750107931; bh=0W3oaKucpq4l/BVEw8nroG4LqtFe0etV3ZPi0IaCQ2U=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=UL/gkN/SKre6OQ5X/2Uls97pnva5BO/5/U4mQ4utL3gqDmKY/PhDB5FWFIJEFGI/3 pWncB5M6cmngqDJw2gTW+ZZKepwp8OnByujelWvg/LikasnF4zwAvLn/li0WJIJ2Gt u4I0aRoXRJJxqqDYYjSqYvDs/S1a5qrvGoxvIwQMxYKQyDdaHnUKHrkrwhzjPytoGF ekraTpUnYjyBalWCoPZ/9509yfkIj7UDA+3K+R/mDsuaQJLvUEgQMP1z+ovzWlVjcy In5HGUVE/B1650hoHh6EHbgtzIKUluNUMwrMA+VIM+4IaTwBuD/VJXpw3HyfxclNEb ubSMnzCQH4ZaQ== Date: Mon, 16 Jun 2025 16:05:30 -0500 From: Bjorn Helgaas To: Graham Whyte Cc: Christoph Hellwig , Niklas Cassel , linux-pci@vger.kernel.org, shyamsaini@linux.microsoft.com, code@tyhicks.com, Okaya@kernel.org, bhelgaas@google.com, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3 0/2] PCI: Reduce FLR delay to 10ms for MSFT devices Message-ID: <20250616210530.GA1106466@bhelgaas> 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: <56b926e8-4b5c-45a8-882e-7c6be0e2fd26@linux.microsoft.com> On Mon, Jun 16, 2025 at 12:02:41PM -0700, Graham Whyte wrote: > On 6/13/2025 8:33 AM, Bjorn Helgaas wrote: > > On Thu, Jun 12, 2025 at 09:41:45AM -0700, Graham Whyte wrote: > >> On 6/11/2025 11:31 PM, Christoph Hellwig wrote: > >>> On Wed, Jun 11, 2025 at 01:08:21PM -0700, Graham Whyte wrote: > >>>> We can ask our HW engineers to implement function readiness but we need > >>>> to be able to support exiting products, hence why posting it as a quirk. > >>> > >>> Your report sounds like it works perfectly fine, it's just that you > >>> want to reduce the delay. For that you'll need to stick to the standard > >>> methods instead of adding quirks, which are for buggy hardware that does > >>> not otherwise work. > >> > >> Bjorn, what would you recommend as next steps here? > > > > This is a tough call and I don't pretend to have an obvious answer. I > > understand the desire to improve performance. On the other hand, PCI > > has been successful over the long term because devices adhere to > > standardized ways of doing things, which makes generic software > > possible. Quirks degrade that story, of course, especially when there > > is an existing standardized solution that isn't being used. I'm not > > at all happy about vendors that decide against the standard solution > > and then ask OS folks to do extra work to compensate. > > Should someone want to implement readiness time reporting down the road, > they'll need to do the same work as patch 1 in this series (making the > flr delay a configurable parameter). Sure. That's a trivial change. The problem is the quirk itself. The Readiness Time Reporting Extended Capability is read-only with no control bits in it so it requires no actual logic in the device. Maybe you can just implement that capability with a firmware change on the device and add the corresponding Linux support for it.