From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (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 12B2B3236 for ; Tue, 4 Jun 2024 12:28:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717504141; cv=none; b=TnftQoavdattTELupqKHnt0VdrshpjlWAuFKeHqcsU57z6dDEo8UoHg+1Vy+vV1OMhhplWiCDNJ1tm+zm4fWeZm8GHz+LRuIAdbLb6J8IlfaU4SY/eqT7Q/RnaFF13GXBK+V4Yp2Q7B9NY9N/xmtej+eT1UaBrOdZxxnkuoEaxc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1717504141; c=relaxed/simple; bh=Zs2KBbYyC9T6QGVbBph93WydZMEkAGWxFBsrOnMNj28=; h=From:To:Cc:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=rTXhllVXTTt1smASF8XUahDiUlF3d9r/uIjUvCXYbSi4x3AeE0xs5Cz7qhm2Ie4daiwIz93iFdXCXwlbkEx5Cf8EZobVzU+Rjyyc4pjyG4QxcIaH5DrOrGYlAPzq6ZJ93Yq19hTY1cnDcERjvaKWyu0pzoVCPlB6BpBDFWNckDA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=a7ZCcok5; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="a7ZCcok5" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1717504139; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=8xDFsrXwaNaInsZ8AxXaZ9DH8FqH1/zcsyoVrAYeJ0o=; b=a7ZCcok5qvs08BI/M8DGHSLmQt+/Ue1N3Edu05hJZOarlTmc8buFY8asvpMW0v7icrVAt9 buGjlBLKzE6VTD0b66yiStT25r9FTh9tG0fsWdGvOIGHN73hzP+WdzZBBBbwYXhq3FyRII XGqXRGYx7XmWM46ZMvO+sOrKUZMmsus= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-111-eD-6wDx8MLqxw7m7qm4rvA-1; Tue, 04 Jun 2024 08:28:57 -0400 X-MC-Unique: eD-6wDx8MLqxw7m7qm4rvA-1 Received: from smtp.corp.redhat.com (int-mx10.intmail.prod.int.rdu2.redhat.com [10.11.54.10]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id BC137811E85; Tue, 4 Jun 2024 12:28:56 +0000 (UTC) Received: from blackfin.pond.sub.org (unknown [10.39.192.93]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6B461492BD1; Tue, 4 Jun 2024 12:28:55 +0000 (UTC) Received: by blackfin.pond.sub.org (Postfix, from userid 1000) id 8BF7A21E66E5; Tue, 4 Jun 2024 14:28:54 +0200 (CEST) From: Markus Armbruster To: Jonathan Cameron Cc: Markus Armbruster , fan , , , , , , , , , , , , Fan Ni Subject: Re: [PATCH v7 09/12] hw/cxl/events: Add qmp interfaces to add/release dynamic capacity extents In-Reply-To: <20240604125428.00003a1d@Huawei.com> (Jonathan Cameron's message of "Tue, 4 Jun 2024 12:54:28 +0100") References: <20240418232902.583744-1-fan.ni@samsung.com> <20240418232902.583744-10-fan.ni@samsung.com> <877cgkxzal.fsf@pond.sub.org> <87h6fkob0t.fsf@pond.sub.org> <20240501155812.00002ec3@Huawei.com> <87cyox9icl.fsf@pond.sub.org> <20240604125428.00003a1d@Huawei.com> Date: Tue, 04 Jun 2024 14:28:54 +0200 Message-ID: <87h6e87uyh.fsf@pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-cxl@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.10 Jonathan Cameron writes: > On Tue, 04 Jun 2024 11:18:18 +0200 > Markus Armbruster wrote: > >> I finally got around to read this slowly. Thank you, Fan and Jonathan! >> >> I'm getting some "incomplete" vibes: "if we ever implement", "patches >> for this on list", "we aren't emulating this yet at all", and ... > > Absolutely. There is a bunch of stuff that we reject today but > the interfaces allow you to specify it and align with the CXL specification > Fabric Management API definition which is the spec used to control this > stuff from a BMC etc. If that doesn't work we have a hardware errata > problem, so hopefully that is fairly stable. > > I think I can publicly confirm there are some related errata in flight, > seeing as we said we'd raise questions on some aspects in the kernel and > QEMU series preceding this one (so no IP secrecy issues). These are as a > result of this work from Fan, but we have carefully avoided implementing > anything that 'may' change. > > >> >> Jonathan Cameron writes: >> >> [...] >> >> > Only thing I'd add is that for now (because we don't need it for testing >> > the kernel flows) is that this does not provide any way for external >> > agents (e.g. our 'fabric manager' to find out what the state is - i.e. >> > if the extents have been accepted by the host etc). That stuff is all >> > defined by the spec, but not yet in the QMP interface. At somepoint >> > we may want to add that as a state query type interface. >> >> ... this, too. >> >> In review of v5, I asked whether this interface needs to be stable. >> >> "Not stable" doesn't mean we change an interface without thought. It >> merely means we can change it much, much faster, and with much less >> overhead. >> >> I understand you want it chiefly for CXL development. Development aids >> commonly don't need to be stable. > > Ok. If it makes sense to make this unstable for now I'm fine with that. > I don't see why it would change beyond in backwards compatible fashion > with new optional fields to cover future specification updates allowing > for more information. However I've been wrong on such things before. > > So I'm fine adding a patch on top of v8 marking them unstable for now. I'd squash it into v8, but follow-up patch works for me, too. >> If you're aiming for stable, you need to convince us the interface can >> support the foreseeable purposes without incompatible changes. In >> particular, I'd like to see how you intend to support "finding out what >> the state is". I suspect that's related to my question in review of v8: >> how to detect completion, and maybe track progress. > > There is a need for completion information but given it's completely > asynchronous to the commands defined here (Can be out of order, lots of > ongoing capacity add / remove flows in flight etc) and for the hardware > definition the feedback occurs via an event record log I'm not expecting it > to affect the interfaces added so far. > >> >> There's infrastructure for background jobs: job.json. We might be >> better off using it, unless completion is trivial and progress tracking >> unnecessary. > > I'll take a look, but these are not conventional background commands > (We do have those as well, but that's a whole different set of future > problems!) > > The actual command itself completes synchronously but not the flow > it kicked off which is not background as such because it may never > finish and involves lots of moving parts. This is similar to any > form of error injection. We inject the error synchronously and that > creates a bunch of records in various registers / firmware etc but > the actions the host OS takes are asynchronous and may only happen > when it decides to poll some register or a driver loads much later. > > So I'm not sure if job.json approach fits. Neither am I, but I want you to be aware of it, so you can make an informed decision :) >> [...]