From: Laszlo Ersek <lersek@redhat.com>
To: "Ni, Ruiyu" <ruiyu.ni@intel.com>, Gary Lin <glin@suse.com>
Cc: "Kinney, Michael D" <michael.d.kinney@intel.com>,
"edk2-devel@lists.01.org" <edk2-devel@ml01.01.org>,
Xen Devel <xen-devel@lists.xen.org>
Subject: Re: [edk2] OVMF broken under Xen (in PCI initialisation)
Date: Thu, 28 Apr 2016 12:35:40 +0200 [thread overview]
Message-ID: <5721E77C.7080701__16685.626973822$1461839820$gmane$org@redhat.com> (raw)
In-Reply-To: <734D49CCEBEEF84792F5B80ED585239D0DA29FD5@SHSMSX103.ccr.corp.intel.com>
On 04/28/16 07:08, Ni, Ruiyu wrote:
>>>> Do you know whether Xen passes the PCI device resource
>>>> information to firmware?
>>
>> I don't think so, no.
>>
>> But, given that the previous PciHostBridgeDxe driver was working on Xen,
>> can we perhaps emulate that behavior in
>> "OvmfPkg/Library/PciHostBridgeLib" somehow?
>
> Let me explain the reason why previous PciHostBridgeDxe driver was
> working on Xen:
> The PciRootBridgeIo.Configuration() in new driver only create resource
> descriptor when the resource status is allocated:
>
> if (ResAllocNode->Status != ResAllocated) {
> continue;
> }
>
> The same function in old driver doesn't check the Status field so it
> unconditionally returns BUS descriptor with AddrRangeMin and
> AddrRangeMax both equal 0. So that PciEnumeratorLight()
> in PciBus driver can still search the devices from starting bus 0.
> It just happened to work.
>
> I think the new driver's Configuration() implementation is correct
> while the old driver's one is wrong. So I don't want to change to
> wrong implementation to fix this issue.
Makes sense, thank you for the explanation.
> The issue can be resolved if we have a way to tell PciBus
> PciEnumeratorLight() which bus number to start searching.
>
> It's almost true that starting bus number for root bridge #0
> is 0. But it might not be true for the rest root bridges.
>
> OVMF's PciHostBridgeLib currently returns multiple root bridges
> and for root bridge #1, the starting bus number is obviously
> not 0 unless "etc/extra-pci-roots" doesn't exist or is 0 so there is
> only one root bridge.
>
> My question is in OVMF over Xen, does "etc/extra-pci-roots" exist?
> If it exists, device behind root bridge #1, #2... can *not* be found
> with the current implementation.
"etc/extra-pci-roots" (more precisely, fw_cfg in general) is specific to
QEMU. QemuFwCfgLib runs alright in Xen guests, but whenever you look for
an fw_cfg file, it is not found -- which is good behavior.
So, OVMF's PciHostBridgeLib produces exactly one PCI_ROOT_BRIDGE object
when it runs on Xen. ExtraRootBridges is set to zero, the loop runs zero
times, and the one InitRootBridge() call after the loop produces one
PCI_ROOT_BRIDGE object, with the following parameters:
- Bus.Base = 0
- Bus.Limit = PCI_MAX_BUS
Thanks
Laszlo
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next prev parent reply other threads:[~2016-04-28 10:35 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20160422144736.GD1885@perard.uk.xensource.com>
2016-04-25 11:43 ` [edk2] OVMF broken under Xen (in PCI initialisation) Laszlo Ersek
[not found] ` <571E02C5.1000906@redhat.com>
2016-04-26 6:29 ` Gary Lin
[not found] ` <20160426062914.GB3109@GaryWorkstation>
2016-04-26 6:45 ` Ni, Ruiyu
2016-04-26 6:43 ` Ni, Ruiyu
[not found] ` <734D49CCEBEEF84792F5B80ED585239D0DA25884@SHSMSX103.ccr.corp.intel.com>
2016-04-26 7:35 ` Gary Lin
[not found] ` <20160426073529.GC3109@GaryWorkstation>
2016-04-26 8:19 ` Ni, Ruiyu
[not found] ` <734D49CCEBEEF84792F5B80ED585239D0DA25B98@SHSMSX103.ccr.corp.intel.com>
2016-04-26 8:40 ` Gary Lin
[not found] ` <20160426084000.GD3109@GaryWorkstation>
2016-04-26 9:40 ` Ni, Ruiyu
[not found] ` <734D49CCEBEEF84792F5B80ED585239D0DA25D38@SHSMSX103.ccr.corp.intel.com>
2016-04-27 4:29 ` Gary Lin
[not found] ` <20160427042907.GH3109@GaryWorkstation>
2016-04-27 5:39 ` Ni, Ruiyu
[not found] ` <734D49CCEBEEF84792F5B80ED585239D0DA27D1E@SHSMSX103.ccr.corp.intel.com>
2016-04-27 6:54 ` Gary Lin
[not found] ` <20160427065428.GJ3109@GaryWorkstation>
2016-04-27 7:18 ` Ni, Ruiyu
[not found] ` <734D49CCEBEEF84792F5B80ED585239D0DA27F59@SHSMSX103.ccr.corp.intel.com>
2016-04-27 8:26 ` Gary Lin
[not found] ` <20160427082641.GK3109@GaryWorkstation>
2016-04-27 9:48 ` Ni, Ruiyu
2016-04-27 9:50 ` Ni, Ruiyu
[not found] ` <734D49CCEBEEF84792F5B80ED585239D0DA291E5@SHSMSX103.ccr.corp.intel.com>
2016-04-27 10:43 ` Laszlo Ersek
[not found] ` <572097E4.1070300@redhat.com>
2016-04-28 5:08 ` Ni, Ruiyu
[not found] ` <734D49CCEBEEF84792F5B80ED585239D0DA29FD5@SHSMSX103.ccr.corp.intel.com>
2016-04-28 9:12 ` Gary Lin
[not found] ` <20160428091209.GL3109@GaryWorkstation>
2016-04-28 9:44 ` Andrew Cooper
2016-04-28 10:35 ` Laszlo Ersek [this message]
[not found] ` <5721E77C.7080701@redhat.com>
2016-05-05 8:03 ` Ni, Ruiyu
[not found] ` <734D49CCEBEEF84792F5B80ED585239D0DA479DB@SHSMSX103.ccr.corp.intel.com>
2016-05-05 9:12 ` Wei Liu
2016-05-05 9:22 ` Gary Lin
2016-04-26 9:31 ` Andrew Cooper
2016-04-26 10:03 ` Gary Lin
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