Re: Question about hotplugging NIC devices to an empty pci-bridge

["Yao, Jiewen" <jiewen.yao@intel.com>]

Maybe you can use EFI_PCI_HOT_PLUG_INIT_PROTOCOL to reserve some resource.

See MdePkg\Include\Protocol\PciHotPlugInit.h

Thank you
Yao Jiewen

> -----Original Message-----
> From: edk2-devel [mailto:edk2-devel-bounces@lists.01.org] On Behalf Of
> Zhoujian (jay)
> Sent: Thursday, December 20, 2018 7:34 PM
> To: edk2-devel@lists.01.org
> Cc: Huangweidong (C) <weidong.huang@huawei.com>; liujunjie (A)
> <liujunjie23@huawei.com>; wangxin (U) <wangxinxin.wang@huawei.com>;
> wujing (O) <wujing42@huawei.com>; dengkai (A) <dengkai1@huawei.com>
> Subject: [edk2] Question about hotplugging NIC devices to an empty
> pci-bridge
> 
> Hi all,
> 
> The issue occurs when I started a virtual machine in UEFI way by libvirt on
> qemu-kvm platform, the vm is configured with 8 pci-bridges on root bus0. I
> hotplug a device like virtual nic to an empty pci-bridge which has no device
> connected. Login the vm, I can see the device by "lspci"", but it didn't show
> by "ifconfig -a". Dmesg shows like below:
> pci 0000:04:01.0: BAR 0: no space for [mem size 0x00010000 64bit pref] pci
> 0000:04:01.0: BAR 0: failed to assign [mem size 0x00010000 64bit pref] pci
> 0000:04:01.0: BAR 3: no space for [mem size 0x00004000 64bit pref] pci
> 0000:04:01.0: BAR 3: failed to assign [mem size 0x00004000 64bit pref]
> 
> Reboot the vm, everything turns back to normal and I can see the new
> hotplugged nic by "ifconfig -a".
> 
> Use the OVMF compiling from latest edk2 source code, the same problem
> arises.
> 
> So, my questions are:
> 1) the generic PCI bus driver in edk2 does not allocate IO and/or MMIO for a
> bridge if there is no device behind the bridge that consume that kind of
> resource?
> 2) What's the purpose of this strategy?
> 3) Why don't allocate resource to all bridges like seabios?
> 4) Is there any switch for me to turn off this constraint so that every
> pci-bridge including empty ones can be assigned IO and memory window?
> Otherwise, each time I hotplug a device to empty pci-bridge, a reboot
> operation should be implemented to use the device?
> 
> Any help will be appreciated, Thanks!
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