From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: Igor Druzhinin <igor.druzhinin@citrix.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: Fri, 6 Sep 2019 18:30:21 -0400 [thread overview]
Message-ID: <5054ad91-5b87-652c-873a-b31758948bd7@oracle.com> (raw)
In-Reply-To: <1567556431-9809-1-git-send-email-igor.druzhinin@citrix.com>
On 9/3/19 8:20 PM, Igor Druzhinin wrote:
> If MCFG area is not reserved in E820, Xen by default will defer its usage
> until Dom0 registers it explicitly after ACPI parser recognizes it as
> a reserved resource in DSDT. Having it reserved in E820 is not
> mandatory according to "PCI Firmware Specification, rev 3.2" (par. 4.1.2)
> and firmware is free to keep a hole E820 in that place. Xen doesn't know
> what exactly is inside this hole since it lacks full ACPI view of the
> platform therefore it's potentially harmful to access MCFG region
> without additional checks as some machines are known to provide
> inconsistent information on the size of the region.
>
> Now xen_mcfg_late() runs after acpi_init() which is too late as some basic
> PCI enumeration starts exactly there. Trying to register a device prior
> to MCFG reservation causes multiple problems with PCIe extended
> capability initializations in Xen (e.g. SR-IOV VF BAR sizing). There are
> no convenient hooks for us to subscribe to so try to register MCFG
> areas earlier upon the first invocation of xen_add_device().
Where is MCFG parsed? pci_arch_init()?
-boris
> Keep the
> existing initcall in case information of MCFG areas is updated later
> in acpi_init().
>
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next prev parent reply other threads:[~2019-09-06 22:32 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 [this message]
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
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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