From: Igor Druzhinin <igor.druzhinin@citrix.com>
To: Jan Beulich <jbeulich@suse.com>,
Boris Ostrovsky <boris.ostrovsky@oracle.com>,
<linux-kernel@vger.kernel.org>
Cc: Juergen Gross <jgross@suse.com>, xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] [PATCH] xen/pci: try to reserve MCFG areas earlier
Date: Tue, 10 Sep 2019 11:08:59 +0100 [thread overview]
Message-ID: <8fa50f93-bc83-3474-8bca-3437f3b47a6e@citrix.com> (raw)
In-Reply-To: <64d52960-28d5-fb23-8892-35c9d4ed9d90@suse.com>
On 10/09/2019 10:55, Jan Beulich wrote:
> On 10.09.2019 11:46, Igor Druzhinin wrote:
>> On 10/09/2019 02:47, Boris Ostrovsky wrote:
>>> On 9/9/19 5:48 PM, Igor Druzhinin wrote:
>>>> 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.
>
> I don't think they're strictly dummy. Even for boot time available devices
> iirc there's no strict requirement for there to be respective data in MCFG.
> Such a requirement exists only for devices which are actually needed to
> start the OS (disk or network, perhaps video or alike), or maybe even just
> its loader.
>
This was my interpretation of 4.1.3 of "PCI Frimware specification":
"Memory mapped configuration base addresses for non-hot pluggable host
bridges must be described using MCFG table." Although, I admit that
"non-hot pluggable" might mean available at boot as well.
Igor
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next prev parent reply other threads:[~2019-09-10 10:10 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-04 0:20 [Xen-devel] [PATCH] xen/pci: try to reserve MCFG areas earlier Igor Druzhinin
2019-09-04 9:08 ` Jan Beulich
2019-09-04 11:36 ` Igor Druzhinin
2019-09-04 12:09 ` Jan Beulich
2019-09-06 22:30 ` Boris Ostrovsky
2019-09-06 23:00 ` Igor Druzhinin
2019-09-08 18:28 ` Boris Ostrovsky
2019-09-08 21:11 ` Igor Druzhinin
2019-09-08 23:30 ` Boris Ostrovsky
2019-09-08 23:37 ` Igor Druzhinin
2019-09-09 19:19 ` Boris Ostrovsky
2019-09-09 21:48 ` Igor Druzhinin
2019-09-10 1:47 ` Boris Ostrovsky
2019-09-10 9:46 ` Igor Druzhinin
2019-09-10 9:55 ` Jan Beulich
2019-09-10 10:08 ` Igor Druzhinin [this message]
2019-09-10 17:48 ` Boris Ostrovsky
2019-09-10 20:36 ` Igor Druzhinin
2019-09-10 21:19 ` Boris Ostrovsky
2019-09-11 1:15 ` Igor Druzhinin
2019-09-11 9:13 ` Jan Beulich
2019-09-12 17:33 ` Boris Ostrovsky
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