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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 463FDC433EF for ; Tue, 28 Sep 2021 06:59:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2CBC7611C0 for ; Tue, 28 Sep 2021 06:59:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239132AbhI1HA5 (ORCPT ); Tue, 28 Sep 2021 03:00:57 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:57648 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239126AbhI1HAw (ORCPT ); Tue, 28 Sep 2021 03:00:52 -0400 Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 1E9E92233E; Tue, 28 Sep 2021 06:59:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1632812349; h=from:from:reply-to: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=8b2olotqmBe8T0BpUmGKRkSj3kbHQqlP9ZL2h4U6D6w=; b=phtozVx+GmmE9nDTx+OxHMDSUVol8CU7ms/13mLHmu9Ca7R51FPGBHNnO6DQZY0toZvuT8 MYN+ihzpcUVfI9Y7V8/UqlLTxosoHJ3IhShAIxiq7x1LXGoKXdTUZa+xbuvR4JR+pmAhG6 RZhIKpdgrV75Li7bMupdYD7AkDLDhGM= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id BB65113513; Tue, 28 Sep 2021 06:59:08 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id rB/CKzy9UmHWVwAAMHmgww (envelope-from ); Tue, 28 Sep 2021 06:59:08 +0000 Subject: Re: [PATCH v4 1/2] xen-pciback: prepare for the split for stub and PV To: Oleksandr Andrushchenko , Jan Beulich , Stefano Stabellini Cc: "boris.ostrovsky@oracle.com" , "julien@xen.org" , "xen-devel@lists.xenproject.org" , "linux-kernel@vger.kernel.org" References: <20210927065822.350973-1-andr2000@gmail.com> <1cf5fbf3-6453-e258-3940-8b5bb96117b6@suse.com> <0b952b8d-0ebd-1c8c-84d4-f02e05bc2a2b@suse.com> From: Juergen Gross Message-ID: Date: Tue, 28 Sep 2021 08:59:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="y4XK9qQ6Q6UB0y5bw2qxgXOrIOa8fCY7M" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --y4XK9qQ6Q6UB0y5bw2qxgXOrIOa8fCY7M Content-Type: multipart/mixed; boundary="WBDbVkRjhr2Xl4zRhV5ApKwybLg9i6LKa"; protected-headers="v1" From: Juergen Gross To: Oleksandr Andrushchenko , Jan Beulich , Stefano Stabellini Cc: "boris.ostrovsky@oracle.com" , "julien@xen.org" , "xen-devel@lists.xenproject.org" , "linux-kernel@vger.kernel.org" Message-ID: Subject: Re: [PATCH v4 1/2] xen-pciback: prepare for the split for stub and PV References: <20210927065822.350973-1-andr2000@gmail.com> <1cf5fbf3-6453-e258-3940-8b5bb96117b6@suse.com> <0b952b8d-0ebd-1c8c-84d4-f02e05bc2a2b@suse.com> In-Reply-To: --WBDbVkRjhr2Xl4zRhV5ApKwybLg9i6LKa Content-Type: multipart/mixed; boundary="------------2FAFFFE2618023AB1523ED08" Content-Language: en-US This is a multi-part message in MIME format. --------------2FAFFFE2618023AB1523ED08 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 28.09.21 08:56, Oleksandr Andrushchenko wrote: >=20 > On 28.09.21 09:42, Jan Beulich wrote: >> On 28.09.2021 06:18, Stefano Stabellini wrote: >>> On Mon, 27 Sep 2021, Juergen Gross wrote: >>>> On 27.09.21 09:35, Oleksandr Andrushchenko wrote: >>>>> On 27.09.21 10:26, Jan Beulich wrote: >>>>>> On 27.09.2021 08:58, Oleksandr Andrushchenko wrote: >>>>>>> From: Oleksandr Andrushchenko >>>>>>> >>>>>>> Currently PCI backend implements multiple functionalities at a ti= me. >>>>>>> To name a few: >>>>>>> 1. It is used as a database for assignable PCI devices, e.g. xl >>>>>>> pci-assignable-{add|remove|list} manipulates that list. So= , >>>>>>> whenever >>>>>>> the toolstack needs to know which PCI devices can be passe= d through >>>>>>> it reads that from the relevant sysfs entries of the pciba= ck. >>>>>>> 2. It is used to hold the unbound PCI devices list, e.g. when pas= sing >>>>>>> through a PCI device it needs to be unbound from the relev= ant >>>>>>> device >>>>>>> driver and bound to pciback (strictly speaking it is not r= equired >>>>>>> that the device is bound to pciback, but pciback is again = used as a >>>>>>> database of the passed through PCI devices, so we can re-b= ind the >>>>>>> devices back to their original drivers when guest domain s= huts >>>>>>> down) >>>>>>> 3. Device reset for the devices being passed through >>>>>>> 4. Para-virtualised use-cases support >>>>>>> >>>>>>> The para-virtualised part of the driver is not always needed as s= ome >>>>>>> architectures, e.g. Arm or x86 PVH Dom0, are not using backend-fr= ontend >>>>>>> model for PCI device passthrough. For such use-cases make the ver= y >>>>>>> first step in splitting the xen-pciback driver into two parts: Xe= n >>>>>>> PCI stub and PCI PV backend drivers. >>>>>>> >>>>>>> Signed-off-by: Oleksandr Andrushchenko >>>>>>> >>>>>>> >>>>>>> --- >>>>>>> Changes since v3: >>>>>>> - Move CONFIG_XEN_PCIDEV_STUB to the second patch >>>>>> I'm afraid this wasn't fully done: >>>>>> >>>>>>> --- a/drivers/xen/xen-pciback/Makefile >>>>>>> +++ b/drivers/xen/xen-pciback/Makefile >>>>>>> @@ -1,5 +1,6 @@ >>>>>>> # SPDX-License-Identifier: GPL-2.0 >>>>>>> obj-$(CONFIG_XEN_PCIDEV_BACKEND) +=3D xen-pciback.o >>>>>>> +obj-$(CONFIG_XEN_PCIDEV_STUB) +=3D xen-pciback.o >>>>>> While benign when added here, this addition still doesn't seem to >>>>>> belong here. >>>>> My bad. So, it seems without CONFIG_XEN_PCIDEV_STUB the change seem= s >>>>> >>>>> to be non-functional. With CONFIG_XEN_PCIDEV_STUB we fail to build = on 32-bit >>>>> >>>>> architectures... >>>>> >>>>> What would be the preference here? Stefano suggested that we still = define >>>>> >>>>> CONFIG_XEN_PCIDEV_STUB, but in disabled state, e.g. we add tristate= to it >>>>> >>>>> in the second patch >>>>> >>>>> Another option is just to squash the two patches. >>>> Squashing would be fine for me. >>> =20 >>> It is fine for me to squash the two patches. >>> >>> But in any case, wouldn't it be better to modify that specific change= to: >>> >>> diff --git a/drivers/xen/xen-pciback/Makefile b/drivers/xen/xen-pciba= ck/Makefile >>> index e2cb376444a6..e23c758b85ae 100644 >>> --- a/drivers/xen/xen-pciback/Makefile >>> +++ b/drivers/xen/xen-pciback/Makefile >>> @@ -1,6 +1,5 @@ >>> # SPDX-License-Identifier: GPL-2.0 >>> -obj-$(CONFIG_XEN_PCIDEV_BACKEND) +=3D xen-pciback.o >>> -obj-$(CONFIG_XEN_PCIDEV_STUB) +=3D xen-pciback.o >>> +obj-$(CONFIG_XEN_PCI_STUB) +=3D xen-pciback.o >> But that wouldn't allow the driver to be a module anymore, would it? >=20 > Exactly. I forgot that when playing with module/built-in I was not able= >=20 > to control that anymore because CONFIG_XEN_PCI_STUB will always be >=20 > in "y" state, thus even if you have CONFIG_XEN_PCIDEV_BACKEND=3Dm >=20 > you won't be able to build it as module. So, I will probably put a comm= ent >=20 > about that in the Makefile explaining the need for >=20 > obj-$(CONFIG_XEN_PCIDEV_BACKEND) +=3D xen-pciback.o > obj-$(CONFIG_XEN_PCIDEV_STUB) +=3D xen-pciback.o In case the real split between both parts of xen-pciback is done this will be needed anyway. 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