Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Received-SPF: None (esa1.hc3370-68.iphmx.com: no sender
  authenticity information available from domain of
  igor.druzhinin@citrix.com) identity=pra;
  client-ip=162.221.158.21; receiver=esa1.hc3370-68.iphmx.com;
  envelope-from="igor.druzhinin@citrix.com";
  x-sender="igor.druzhinin@citrix.com";
  x-conformance=sidf_compatible
Received-SPF: Pass (esa1.hc3370-68.iphmx.com: domain of
  igor.druzhinin@citrix.com designates 162.221.158.21 as
  permitted sender) identity=mailfrom;
  client-ip=162.221.158.21; receiver=esa1.hc3370-68.iphmx.com;
  envelope-from="igor.druzhinin@citrix.com";
  x-sender="igor.druzhinin@citrix.com";
  x-conformance=sidf_compatible; x-record-type="v=spf1";
  x-record-text="v=spf1 ip4:209.167.231.154 ip4:178.63.86.133
  ip4:195.66.111.40/30 ip4:85.115.9.32/28 ip4:199.102.83.4
  ip4:192.28.146.160 ip4:192.28.146.107 ip4:216.52.6.88
  ip4:216.52.6.188 ip4:162.221.158.21 ip4:162.221.156.83 ~all"
Received-SPF: None (esa1.hc3370-68.iphmx.com: no sender
  authenticity information available from domain of
  postmaster@mail.citrix.com) identity=helo;
  client-ip=162.221.158.21; receiver=esa1.hc3370-68.iphmx.com;
  envelope-from="igor.druzhinin@citrix.com";
  x-sender="postmaster@mail.citrix.com";
  x-conformance=sidf_compatible
IronPort-SDR: AgY4YBa9SZqZDb2XZGfDW/N/bNhCxk6gnc2o2rZCbMaDE3QDyLj0qR8AcffIrNjy3l47IcJjCJ
 91YXehax9cFUWunmd/Pz0pRv3xtClo5f0V6h4T6tNLJKVz8gdGw0hvY4tfScQ9uGDkGrTb3lPd
 jVEIW6+6VXkyyzp6qeZXEAO668ZXtQkp/lanCnBB+8PbjgMffgZhu/vgbRBYC3VykCrFAiUV94
 X4OrxJH8BO0gmRkbvG4dkC3bW5UKNSy96+8lyfDkmj3cELv/B+rTFmV0J3pE+unFjDxCdUe0z4
 Lws=
Subject: Re: [Xen-devel] [PATCH] xen/pci: try to reserve MCFG areas earlier
To:     Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        <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>
 <e3114d56-51cd-b973-1ada-f6a60a7e99cc@citrix.com>
 <43b7da04-5c42-80d8-898b-470ee1c91ed2@oracle.com>
 <adefac87-c2b3-b67f-fb4d-d763ce920bef@citrix.com>
 <1695c88d-e5ad-1854-cdef-3cd95c812574@oracle.com>
 <4d3bf854-51de-99e4-9a40-a64c581bdd10@citrix.com>
 <bc3da154-d451-02cf-6154-5e0dc721a6e6@oracle.com>
 <c45b8786-5735-a95d-bc40-61372c326037@citrix.com>
 <43e492ff-f967-7218-65c4-d16581fabea3@oracle.com>
From:   Igor Druzhinin <igor.druzhinin@citrix.com>
Message-ID: <416ff4b7-3186-f61a-75fa-bcfc968f8117@citrix.com>
Date:   Tue, 10 Sep 2019 10:46:38 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101
 Thunderbird/60.8.0
MIME-Version: 1.0
In-Reply-To: <43e492ff-f967-7218-65c4-d16581fabea3@oracle.com>
Content-Type: text/plain; charset="utf-8"
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

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. 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.

Igor