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Re: [Xen-users] VGA PASSTHROUGH not working :(

So the iommu /should/ be working at this point. Now we just need to hide the graphics card from the Dom0 operating system.

Check if xen-pciback is a module using `modprobe -v xen-pciback` or `lsmod | grep xen-pciback`. If xen-pciback is built as a module on your system, you need to make sure that your graphics driver a) is a module and not compiled-in, and b) the graphics driver cannot be loaded before xen-pciback (the article tells you how to achieve this), even in early userspace! I would recommend blacklisting the graphics driver too, just to be safe.

See this article for the various methods of hiding PCI devices and the syntax to do so.

As I said before, you'll want your DomU utilizing passthrough to be automatically started up on boot, because you probably won't be able to see anything on the screen until the DomU starts.

Quoting Jason Long <hack3rcon@xxxxxxxxx>:

I added but :
[root@localhost ~]# xl dmesg | grep iommu
(XEN) Command line: intel_iommu=on placeholder
[root@localhost ~]# xl pci-
pci-assignable-add      pci-assignable-remove   pci-detach 
pci-assignable-list     pci-attach              pci-list 
[root@localhost ~]# xl pci-assignable-list 
[root@localhost ~]# 

On Monday, May 16, 2016 12:56 PM, De Coro Guillaume <guillaumedecoro@xxxxxxxxx> wrote:


I'm not a great user of xen but I known several things. sm8ax1 is right. It seems you are missing IOMMU. Don't forget to add "intel_iommu=on" in your grub default. If it works you can see that in your dmesg:
[    0.000000] DMAR: IOMMU enabled
[    0.078793] DMAR-IR: IOAPIC id 2 under DRHD base  0xfed91000 IOMMU 1
[    0.865169] iommu: Adding device 0000:00:00.0 to group 0
[    0.865179] iommu: Adding device 0000:00:02.0 to group 1
[    0.865194] iommu: Adding device 0000:00:14.0 to group 2
[    0.865204] iommu: Adding device 0000:00:14.2 to group 2
[    0.865215] iommu: Adding device 0000:00:16.0 to group 3
[    0.865225] iommu: Adding device 0000:00:17.0 to group 4
[    0.865243] iommu: Adding device 0000:00:1c.0 to group 5
[    0.865257] iommu: Adding device 0000:00:1c.2 to group 5
[    0.865280] iommu: Adding device 0000:00:1f.0 to group 6
[    0.865294] iommu: Adding device 0000:00:1f.2 to group 6
[    0.865303] iommu: Adding device 0000:00:1f.3 to group 6
[    0.865312] iommu: Adding device 0000:00:1f.4 to group 6
[    0.865321] iommu: Adding device 0000:00:1f.6 to group 6
[    0.865329] iommu: Adding device 0000:01:00.0 to group 5
[    0.865338] iommu: Adding device 0000:02:00.0 to group 5

and about DMAR:

[    0.000000] ACPI: DMAR 0x00000000A52B3000 0000A8 (v01 INTEL  SKL      00000001 INTL 00000001)
[    0.000000] DMAR: IOMMU enabled
[    0.078747] DMAR: Host address width 39
[    0.078751] DMAR: DRHD base: 0x000000fed90000 flags: 0x0
[    0.078769] DMAR: dmar0: reg_base_addr fed90000 ver 1:0 cap 1c0000c40660462 ecap 7e3ff0505e
[    0.078775] DMAR: DRHD base: 0x000000fed91000 flags: 0x1
[    0.078781] DMAR: dmar1: reg_base_addr fed91000 ver 1:0 cap d2008c40660462 ecap f050da
[    0.078786] DMAR: RMRR base: 0x000000a4eff000 end: 0x000000a4f1efff
[    0.078789] DMAR: RMRR base: 0x000000a5800000 end: 0x000000a7ffffff
[    0.078793] DMAR-IR: IOAPIC id 2 under DRHD base  0xfed91000 IOMMU 1
[    0.078796] DMAR-IR: HPET id 0 under DRHD base 0xfed91000
[    0.078799] DMAR-IR: x2apic is disabled because BIOS sets x2apic opt out bit.
[    0.078801] DMAR-IR: Use 'intremap=no_x2apic_optout' to override the BIOS setting.
[    0.080255] DMAR-IR: Enabled IRQ remapping in xapic mode
[    0.864755] DMAR: No ATSR found
[    0.864868] DMAR: dmar0: Using Queued invalidation
[    0.864992] DMAR: dmar1: Using Queued invalidation
[    0.865000] DMAR: Setting RMRR:
[    0.865022] DMAR: Setting identity map for device 0000:00:02.0 [0xa5800000 - 0xa7ffffff]
[    0.865037] DMAR: Setting identity map for device 0000:00:14.0 [0xa4eff000 - 0xa4f1efff]
[    0.865047] DMAR: Prepare 0-16MiB unity mapping for LPC
[    0.865093] DMAR: Setting identity map for device 0000:00:1f.0 [0x0 - 0xffffff]
[    0.865112] DMAR: Intel(R) Virtualization Technology for Directed I/O

It's important not to claim your passthroughed hardware by dom0. Just use "pci_stub" parameters in your grub default. After that, your command "xl pci-assignable-list" will give your video card available.

About IGD passthrough, I'm working on it without success for monthes. Maybe I'm wrong, but XenGT build fail for me. I'm using an Intel i3 6100T with Intel HD 530. I saw that Xen 4.7 will handle some igd passthrough parameters. So wait and see... and try it :)


Le 14/05/2016 14:56, sm8ax1@xxxxxxxxxxx a écrit :


Well, it looks to me like you don't have an IOMMU. You can check your Intel processor http://ark.intel.com/ and look for "VT-d" support. There is probably a similar site for AMD, but they call it "IOMMU" support; same thing just different names. There might also be some way to check through `lshw` or `/proc/cpuinfo` or the like, but I don't know for sure.

The wiki mentions that generic PCI passthrough might still work on some graphics cards, even without an IOMMU, but I imagine your chances are pretty slim. Something to try perhaps is setting up your HVM to automatically start when the system is booted, with generic PCI passthrough enabled, and blacklist the module on the Dom0 and reboot. In theory this prevents the Dom0 driver from interfering with the HVM's configuration of the graphics card, but once again, it might work or it might not.


If that doesn't work, your options are buy a new PC/processor with an IOMMU, or use VNC, Spice, SDL, GTK, etc. with userspace frontends in the Dom0. Spice with the QXL video driver is likely to give you the best performance, but even it won't compete with that of VGA passthrough.


If you go the route of upgrading your hardware, XenGT (now called "GVT-v for Xen") is something else to look into. The idea behind it is to allow multiple VMs to simultaneously use VGA passthrough in a safe and performant manner by creating multiple virtual graphics cards at the hardware level. At least as of Jan 2015, XenGT is being developed out-of-tree, but I haven't followed up on it as to whether it's been merged (or abandoned). If I recall correctly, this is supported on Intel 6th generation and newer processors with Intel HD 6000+ graphics, but you should definitely double check that.


There used to be something called "Paravirtualized DRM", which probably worked like the paravirtualized framebuffer, only using the newer and faster Linux DRM API. This, I guess, would have allowed multiple rendering clients across multiple VMs to directly render their window contents just as they would on baremetal (with the PV DRM driver acting as a shim), without any kind of VGA/PCI passthrough. Unfortunately this effort has been abandoned, and I've been unable to track down the author or even the original code.


Quoting Jason Long <hack3rcon@xxxxxxxxx>:
I want to use my VGA in VM that running Windows 7, My VGA information is :
01:00.0 VGA compatible controller: NVIDIA Corporation GT218 [GeForce 210] (rev a2)
Subsystem: ASUSTeK Computer Inc. Device 8354
Kernel driver in use: nouveau
Kernel modules: nouveau
And :
[root@localhost ~]# xl pci-assignable-list 
[root@localhost ~]# 
And I added below lines to my VM config file :
pci=['01:00.0 ']
but when I want fire my VM, It show me below error :
libxl: error: libxl_pci.c:1089:libxl__device_pci_add: PCI device 0000:01:00.0 cannot be assigned - no IOMMU?
libxl: error: libxl_create.c:1405:domcreate_attach_pci: libxl_device_pci_add failed: -1
libxl: info: libxl.c:1698:devices_destroy_cb: forked pid 3365 for destroy of domain 3
How can I solve it?


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