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Re: [Xen-users] PCI Passthrough for an HVM?

On Mon, 2015-10-05 at 19:36 +0000, Eric wrote:
> ...I don't see anything that looks like it controls the permissive
> attribute of the device.
> What have I overlooked?

The permissiveness is set in the guest cfg file, either as a global option
or as an key in the pci= entry for the specific device. I've just noticed
that xl.cfg(5) describes both of these as PV only, which is not true. I'll
send a patch shortly.

For HVM guests pciback is not involved in passthrough, rather it is QEMU
which does this. Since XSA-131[0] qemu-xen (the upstream variant) has
defaulted to non-permissive mode, and you need to specify permissive in the
config file, which would require you to also have "tools: libxl: allow
permissive qemu-upstream pci passthrough."[1]. I could have sworn that it
was backported but I can't find it in 4.5 or earlier. I've just requested
that now.

Prior to XSA-130 qemu-xen was permissive by default. qemu-traditional (the
old fork) and PV using pciback have always defaulted to non-permissive,



[0] http://xenbits.xen.org/xsa/advisory-131.html

> Eric Pretorious
> Portland, OR
> * https://www.centos.org/forums/viewtopic.php?f=14&t=54409
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