From: Igor Druzhinin <igor.druzhinin@citrix.com>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
<xen-devel@lists.xenproject.org>, <linux-kernel@vger.kernel.org>
Cc: jgross@suse.com
Subject: Re: [Xen-devel] [PATCH] xen/pci: try to reserve MCFG areas earlier
Date: Sun, 8 Sep 2019 22:11:39 +0100 [thread overview]
Message-ID: <adefac87-c2b3-b67f-fb4d-d763ce920bef@citrix.com> (raw)
In-Reply-To: <43b7da04-5c42-80d8-898b-470ee1c91ed2@oracle.com>
On 08/09/2019 19:28, Boris Ostrovsky wrote:
> On 9/6/19 7:00 PM, Igor Druzhinin wrote:
>>
>> On 06/09/2019 23:30, Boris Ostrovsky wrote:
>>>
>>> Where is MCFG parsed? pci_arch_init()?
>>>> It happens twice:
>> 1) first time early one in pci_arch_init() that is arch_initcall - that
>> time pci_mmcfg_list will be freed immediately there because MCFG area is
>> not reserved in E820;
>> 2) second time late one in acpi_init() which is subsystem_initcall right
>> before where PCI enumeration starts - this time ACPI tables will be
>> checked for a reserved resource and pci_mmcfg_list will be finally
>> populated.
>>
>> The problem is that on a system that doesn't have MCFG area reserved in
>> E820 pci_mmcfg_list is empty before acpi_init() and our PCI hooks are
>> called in the same place. So MCFG is still not in use by Xen at this
>> point since we haven't reached our xen_mcfg_late().
>
>
> 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)
b) given (a) we cannot do it ourselves before acpi_init and after is too
late as we're already past ACPI PCI enumeration
c) we'd have to do it in the same place I call xen_mcfg_late() and it'd
be code duplication of what's already done by the existing code.
Igor
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next prev parent reply other threads:[~2019-09-08 21:12 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 [this message]
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
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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