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[Xen-devel] VT-D CPU ressources

  • To: <xen-devel@xxxxxxxxxxxxx>
  • From: "amiard brice" <perso@xxxxxxxxxxxxxxx>
  • Date: Tue, 3 Jul 2012 13:09:15 +0200
  • Delivery-date: Tue, 03 Jul 2012 11:09:22 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xen.org>
  • Thread-index: Ac1YQ6ip6DjfhtQhSiKyn9pet1/2EgAyJX1w



I’ve post a message on xen-users@xxxxxxxxxxxx , according to a member of this list, I’ve decide to post it on xen-devel.


See mailing-list copy above :


This sounds like a question it would be useful to ask on xen-devel.

(Unfortuantely I'm not familiar enough with PCIe-to-PCI bridges to give you a good answer.)





> In my opinion it could be due to the EPT table. In my "xm dmesg" I

> could see "EPT not enable" and "CPU capabilities :  EPT table 2Mo",

> but I can't active it (I've try different options in default/grub

> without succes)


> (if devices behind the same pci bridges could not be allocated to

> different VMs, it' simply because VT-d use specific interruption

> command call MSI-X in aim to identify a domU, and those interruptions

> commands  could be possible only with PCIe, you can have more information in the pdf intel VT-d).


> thank you for your help in advance

> Amiard Brice



>> 2012/6/22 amiard brice <perso@xxxxxxxxxxxxxxx>:


>> I want create four domU with 2 PCI device per dom.


>> I've bought a backplane ("motherboard extension") with 4 bridges PCIe 1x to PCI

>> directly connected to the PCH (Q67).

>>And I have one domU for each "PCI-e to PCI

>> bridge", so according to the intel_VT-d pdf, it could be possible in

>> my case to have 4 domU (one for each PCIe to PCI bridges).



>> (Moreover PCI card (ethernet card) are composed with a PCI bridge)




>> I've succefuly created 4 domU with bakend devices, with option

>> "pci-backend-strict-check" disable.


>> I’ve try with it but even if all PCI ports behind “PCIe to PCI bridge “

>> appears in  pci-list-assignable-devices, domU won’t start, with an

>> error message "device XX:XX.X need to be co-assigned with XX:XX.X,

>> but it's not owned by pci-backend




>> The probleme is :  even if my domU are configuer with 1 VCPUs for

>> each of them, when domU acces to I/O devices, VCPUs aren't separated

>> (I've notice this using virt-manager charts). During a basic CPU

>> benchmark on a domU, VCPUs are isolated.




>> I Have attached "lspci-v", "xm dmesg", "xm

>> pci-list-assignable-devices", "default-grub", "xm info" and a “domU

>> cfg file”


>> For example when I transfer some file between

>> a other PC and a domU through the Ethernet card

>> connected using VT-d, VCPU's charts are identical between each

>> domU (it's like if I/O instruction aren't separated between CPU cores,

>> I think XEN can't determine CPU cores assignation for d'I/O,

>>so it execute instruction on each CPU,

>>and after DMA remapping transfer data to the correct domU).





>> A share core is very problematic my RT application




>> thank you for your help in advance



Attachment: default_grub.txt
Description: Text document

Attachment: lspci_v.txt
Description: Text document

Attachment: qnx_1.config
Description: Binary data

Attachment: xm_dmesg.txt
Description: Text document

Attachment: xm_info.txt
Description: Text document

Attachment: xm_pci_list_assi.txt
Description: Text document

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