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 67B2CC433F5 for ; Tue, 28 Sep 2021 07:26:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 45BB261058 for ; Tue, 28 Sep 2021 07:26:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239256AbhI1H1u (ORCPT ); Tue, 28 Sep 2021 03:27:50 -0400 Received: from smtp-out1.suse.de ([195.135.220.28]:34268 "EHLO smtp-out1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239099AbhI1H1r (ORCPT ); Tue, 28 Sep 2021 03:27:47 -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 18DA522286; Tue, 28 Sep 2021 07:26:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1632813967; 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=jQCgZdE7pv4+WIIfiYvyIaTfRhRo+++4IApjitHJov8=; b=I2C+IOaATHyAeIyxWtVFlb9RqisPyWOEN27HuyFxgZ9RL0tG96ih6aiQvU+YtpnR3aXoUB pghBdJL07/kF3eHQM0cpHmBBB0ZhDZg+YQbIFy6gVJnOFED3tBwQRY6tZ0DMGxkL5lSRJJ N7txiTmBajKUXH+ru/zFjBPn2BOokZI= 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 D9A2413ACF; Tue, 28 Sep 2021 07:26:06 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id YTfDM47DUmGjZAAAMHmgww (envelope-from ); Tue, 28 Sep 2021 07:26:06 +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> <51e38ddc-49df-2e70-d094-71d045297ab1@epam.com> <2b4dc684-a00f-1a08-92b0-7b0b614aeb24@suse.com> From: Juergen Gross Message-ID: Date: Tue, 28 Sep 2021 09:26:06 +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="xIeC2D0vfBQmQvhVmgsuyjJnjFIpMibVn" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --xIeC2D0vfBQmQvhVmgsuyjJnjFIpMibVn Content-Type: multipart/mixed; boundary="bxvJ1mioIrQTt0VSI5fRg2vdvvJnyBynD"; 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> <51e38ddc-49df-2e70-d094-71d045297ab1@epam.com> <2b4dc684-a00f-1a08-92b0-7b0b614aeb24@suse.com> In-Reply-To: --bxvJ1mioIrQTt0VSI5fRg2vdvvJnyBynD Content-Type: multipart/mixed; boundary="------------30492A6117F16F81287211C1" Content-Language: en-US This is a multi-part message in MIME format. --------------30492A6117F16F81287211C1 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable On 28.09.21 09:24, Oleksandr Andrushchenko wrote: >=20 > On 28.09.21 10:20, Juergen Gross wrote: >> On 28.09.21 09:17, Oleksandr Andrushchenko wrote: >>> >>> On 28.09.21 09:59, Juergen Gross wrote: >>>> On 28.09.21 08:56, Oleksandr Andrushchenko wrote: >>>>> >>>>> 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 time. >>>>>>>>>>> To name a few: >>>>>>>>>>> 1. It is used as a database for assignable PCI devices, e.g. = xl >>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 pci-assignable-{a= dd|remove|list} manipulates that list. So, >>>>>>>>>>> whenever >>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 the toolstack nee= ds to know which PCI devices can be passed through >>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 it reads that fro= m the relevant sysfs entries of the pciback. >>>>>>>>>>> 2. It is used to hold the unbound PCI devices list, e.g. when= passing >>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 through a PCI dev= ice it needs to be unbound from the relevant >>>>>>>>>>> device >>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 driver and bound = to pciback (strictly speaking it is not required >>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 that the device i= s bound to pciback, but pciback is again used as a >>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 database of the p= assed through PCI devices, so we can re-bind the >>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 devices back to t= heir original drivers when guest domain shuts >>>>>>>>>>> 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 some >>>>>>>>>>> architectures, e.g. Arm or x86 PVH Dom0, are not using backen= d-frontend >>>>>>>>>>> model for PCI device passthrough. For such use-cases make the= very >>>>>>>>>>> first step in splitting the xen-pciback driver into two parts= : Xen >>>>>>>>>>> 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 @@ >>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 # SPDX-License-Identifier: GP= L-2.0 >>>>>>>>>>> =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 obj-$(CONFIG_XEN_PCIDEV_BACKE= ND) +=3D xen-pciback.o >>>>>>>>>>> +obj-$(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 = seems >>>>>>>>> >>>>>>>>> to be non-functional. With CONFIG_XEN_PCIDEV_STUB we fail to bu= ild on 32-bit >>>>>>>>> >>>>>>>>> architectures... >>>>>>>>> >>>>>>>>> What would be the preference here? Stefano suggested that we st= ill define >>>>>>>>> >>>>>>>>> CONFIG_XEN_PCIDEV_STUB, but in disabled state, e.g. we add tris= tate to it >>>>>>>>> >>>>>>>>> in the second patch >>>>>>>>> >>>>>>>>> Another option is just to squash the two patches. >>>>>>>> Squashing would be fine for me. >>>>>>> =C2=A0=C2=A0=C2=A0 It is fine for me to squash the two patches. >>>>>>> >>>>>>> But in any case, wouldn't it be better to modify that specific ch= ange to: >>>>>>> >>>>>>> diff --git a/drivers/xen/xen-pciback/Makefile b/drivers/xen/xen-p= ciback/Makefile >>>>>>> index e2cb376444a6..e23c758b85ae 100644 >>>>>>> --- a/drivers/xen/xen-pciback/Makefile >>>>>>> +++ b/drivers/xen/xen-pciback/Makefile >>>>>>> @@ -1,6 +1,5 @@ >>>>>>> =C2=A0=C2=A0=C2=A0 # 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-$(CONFIG_XEN_PCI_STUB) +=3D xen-pciback.o >>>>>> But that wouldn't allow the driver to be a module anymore, would i= t? >>>>> >>>>> Exactly. I forgot that when playing with module/built-in I was not = able >>>>> >>>>> to control that anymore because CONFIG_XEN_PCI_STUB will always be >>>>> >>>>> in "y" state, thus even if you have CONFIG_XEN_PCIDEV_BACKEND=3Dm >>>>> >>>>> you won't be able to build it as module. So, I will probably put a = comment >>>>> >>>>> about that in the Makefile explaining the need for >>>>> >>>>> obj-$(CONFIG_XEN_PCIDEV_BACKEND) +=3D xen-pciback.o >>>>> obj-$(CONFIG_XEN_PCIDEV_STUB) +=3D xen-pciback.o >>>> >>>> In case the real split between both parts of xen-pciback is done thi= s >>>> will be needed anyway. >>> >>> Yes, it will >>> >>> So, I'll put a comment in the Makefile: >>> >>> # N.B. This cannot be expressed with a single line using CONFIG_XEN_P= CI_STUB >>> >>> # as it always remains in "y" state, thus preventing the driver to be= built as >>> >>> # a module. >>> >>> obj-$(CONFIG_XEN_PCIDEV_BACKEND) +=3D xen-pciback.o >>> obj-$(CONFIG_XEN_PCIDEV_STUB) +=3D xen-pciback.o >>> >>> Will this be ok or needs some re-wording? >> >> I'd add that CONFIG_XEN_PCIDEV_BACKEND and CONFIG_XEN_PCIDEV_STUB are >> mutually exclusive. > # N.B. The below cannot be expressed with a single line using > # CONFIG_XEN_PCI_STUB as it always remains in "y" state, > # thus preventing the driver to be built as a module. > # Please note, that CONFIG_XEN_PCIDEV_BACKEND and > # CONFIG_XEN_PCIDEV_STUB are mutually exclusive. > obj-$(CONFIG_XEN_PCIDEV_BACKEND) +=3D xen-pciback.o > obj-$(CONFIG_XEN_PCIDEV_STUB) +=3D xen-pciback.o Yes, that's fine. 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