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Tue, 10 Sep 2019 17:48:21 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x8AHheAV006059; Tue, 10 Sep 2019 17:48:20 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3030.oracle.com with ESMTP id 2uwpjw4g6g-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 10 Sep 2019 17:48:20 +0000 Received: from abhmp0005.oracle.com (abhmp0005.oracle.com [141.146.116.11]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id x8AHmJ0k000816; Tue, 10 Sep 2019 17:48:19 GMT Received: from bostrovs-us.us.oracle.com (/10.152.32.65) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 10 Sep 2019 10:48:19 -0700 Subject: Re: [Xen-devel] [PATCH] xen/pci: try to reserve MCFG areas earlier To: Igor Druzhinin , xen-devel@lists.xenproject.org, linux-kernel@vger.kernel.org Cc: jgross@suse.com References: <1567556431-9809-1-git-send-email-igor.druzhinin@citrix.com> <5054ad91-5b87-652c-873a-b31758948bd7@oracle.com> <43b7da04-5c42-80d8-898b-470ee1c91ed2@oracle.com> <1695c88d-e5ad-1854-cdef-3cd95c812574@oracle.com> <4d3bf854-51de-99e4-9a40-a64c581bdd10@citrix.com> <43e492ff-f967-7218-65c4-d16581fabea3@oracle.com> <416ff4b7-3186-f61a-75fa-bcfc968f8117@citrix.com> From: Boris Ostrovsky Openpgp: preference=signencrypt Autocrypt: addr=boris.ostrovsky@oracle.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0 MIME-Version: 1.0 In-Reply-To: <416ff4b7-3186-f61a-75fa-bcfc968f8117@citrix.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Language: en-US X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9376 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=0 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1909100171 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9376 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1906280000 definitions=main-1909100171 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 9/10/19 5:46 AM, Igor Druzhinin wrote: > On 10/09/2019 02:47, Boris Ostrovsky wrote: >> On 9/9/19 5:48 PM, Igor Druzhinin wrote: >>> On 09/09/2019 20:19, Boris Ostrovsky wrote: >>>> On 9/8/19 7:37 PM, Igor Druzhinin wrote: >>>>> On 09/09/2019 00:30, Boris Ostrovsky wrote: >>>>>> On 9/8/19 5:11 PM, Igor Druzhinin wrote: >>>>>>> On 08/09/2019 19:28, Boris Ostrovsky wrote: >>>>>>>> Would it be possible for us to parse MCFG ourselves in pci_xen_init()? I >>>>>>>> realize that we'd be doing this twice (or maybe even three times since >>>>>>>> apparently both pci_arch_init()  and acpi_ini() do it). >>>>>>>> >>>>>>> I don't thine it makes sense: >>>>>>> a) it needs to be done after ACPI is initialized since we need to parse >>>>>>> it to figure out the exact reserved region - that's why it's currently >>>>>>> done in acpi_init() (see commit message for the reasons why) >>>>>> Hmm... We should be able to parse ACPI tables by the time >>>>>> pci_arch_init() is called. In fact, if you look at >>>>>> pci_mmcfg_early_init() you will see that it does just that. >>>>>> >>>>> The point is not to parse MCFG after acpi_init but to parse DSDT for >>>>> reserved resource which could be done only after ACPI initialization. >>>> OK, I think I understand now what you are trying to do --- you are >>>> essentially trying to account for the range inserted by >>>> setup_mcfg_map(), right? >>>> >>> Actually, pci_mmcfg_late_init() that's called out of acpi_init() - >>> that's where MCFG areas are properly sized. >> pci_mmcfg_late_init() reads the (static) MCFG, which doesn't need DSDT parsing, does it? setup_mcfg_map() OTOH does need it as it uses data from _CBA (or is it _CRS?), and I think that's why we can't parse MCFG prior to acpi_init(). So what I said above indeed won't work. >> > No, it uses is_acpi_reserved() (it's called indirectly so might be well > hidden) to parse DSDT to find a reserved resource in it and size MCFG > area accordingly. Right, I see it. Thanks for the explanation. > setup_mcfg_map() is called for every root bus > discovered and indeed tries to evaluate _CBA but at this point > pci_mmcfg_late_init() has already finished MCFG registration for every > cold-plugged bus (which information is described in MCFG table) so those > calls are dummy. > >>> setup_mcfg_map() is mostly >>> for bus hotplug where MCFG area is discovered by evaluating _CBA method; >>> for cold-plugged buses it just confirms that MCFG area is already >>> registered because it is mandated for them to be in MCFG table at boot time. >>> >>>> The other question I have is why you think it's worth keeping >>>> xen_mcfg_late() as a late initcall. How could MCFG info be updated >>>> between acpi_init() and late_initcalls being run? I'd think it can only >>>> happen when a new device is hotplugged. >>>> >>> It was a precaution against setup_mcfg_map() calls that might add new >>> areas that are not in MCFG table but for some reason have _CBA method. >>> It's obviously a "firmware is broken" scenario so I don't have strong >>> feelings to keep it here. Will prefer to remove in v2 if you want. >> Isn't setup_mcfg_map() called before the first xen_add_device() which is where you are calling xen_mcfg_late()? >> > setup_mcfg_map() calls are done in order of root bus discovery which > happens *after* the previous root bus has been enumerated. So the order > is: call setup_mcfg_map() for root bus 0, find that > pci_mmcfg_late_init() has finished MCFG area registration, perform PCI > enumeration of bus 0, call xen_add_device() for every device there, call > setup_mcfg_map() for root bus X, etc. Ah, yes. Multiple busses. If that's the case then why don't we need to call xen_mcfg_late() for the first device on each bus? -boris