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xl.cfg: gfx_passthru documentation improvements
gfx_passthru: Document gfx_passthru makes the GPU become primary in the guest and other generic info about gfx_passthru. Signed-off-by: Pasi Kärkkäinen <pasik@iki.fi> Acked-by: Ian Campbell <ian.campbell@citrix.com> Committed-by: Ian Campbell <ian.campbell@citrix.com>
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@@ -992,7 +992,44 @@ certainly belong in a more appropriate section.
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=item B<gfx_passthru=BOOLEAN>
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Enable graphics device PCI passthrough. XXX which device is passed through ?
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Enable graphics device PCI passthrough. This option makes the passthru
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graphics card become primary graphics card in the VM, so the Qemu emulated
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graphics adapter is disabled, and the VNC console for the VM won't have
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any graphics output. All graphics output, including boot time Qemu BIOS
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messages from the VM, will go to the physical outputs of the passed thru
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physical graphics card.
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Graphics card PCI device to passthru is chosen with B<pci> option,
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exactly in the same way as normal Xen PCI device passthru/assignment is done.
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Note that gfx_passthru doesn't do any kind of sharing
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of the GPU, so you can only assign the GPU to one single VM at a time.
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gfx_passthru also enables various legacy VGA memory ranges, BARs, MMIOs,
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and ioports to be passed thru to the VM, since those are required
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for correct operation of things like VGA BIOS, text mode, VBE, etc.
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Enabling gfx_passthru option also copies the physical graphics card
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video BIOS to the guest memory, and executes the VBIOS in the guest
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to get the graphics card initialized.
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Most graphics adapters require vendor specific tweaks for properly
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working graphics passthru. See the XenVGAPassthroughTestedAdapters
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L<http://wiki.xen.org/wiki/XenVGAPassthroughTestedAdapters>
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wiki page for currently supported graphics cards for gfx_passthru.
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gfx_passthru is currently only supported with the qemu-xen-traditional
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device-model. Upstream qemu-xen device-model currently doesn't have
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support for gfx_passthru.
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Note that some graphics adapters (AMD/ATI cards, for example) don't
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necessarily require gfx_passthru option, so you can use the normal
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Xen PCI passthru to assign the graphics card as a secondary graphics card
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to the VM. Qemu emulated graphics card stays as the primary graphics card,
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and you get VNC output from the Qemu-emulated primary adapter.
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More information about Xen gfx_passthru feature is available
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on the XenVGAPassthrough L<http://wiki.xen.org/wiki/XenVGAPassthrough>
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wiki page.
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=item B<nomigrate=BOOLEAN>
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