Messages in this thread | | | Date | Sun, 22 Jun 2014 16:25:29 +0800 | From | "Chen, Tiejun" <> | Subject | Re: [RFC][PATCH] gpu:drm:i915:intel_detect_pch: back to check devfn instead of check class type |
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On 2014/6/20 20:48, Paolo Bonzini wrote: > Il 19/06/2014 11:53, Tiejun Chen ha scritto: >> so this mean that isa bridge is still represented with Dev31:Func0 >> like the native OS. Furthermore, currently we're pushing VGA >> passthrough support into qemu upstream, and with some discussion, >> we wouldn't set the bridge class type and just expose this devfn. > > Even this is not really optimal. It just happens to work just because > QEMU's machine is currently a PCI machine with the ISA bridge on 00:01.0. > > As soon as you'll try doing integrated graphics passthrough on a PCIe > machine type (such as QEMU's "-M q35") things will break down just as > badly. >
Sorry, I can't understand why this is related to the ISA bridge, 00:01.0 or even other PCIe machine type.
In virtualized case we always need to create this ISA bridge as a devfn, 00:15.0, work for the i915 driver to support IGD passthrough.
In qemu-xen-traditional, this ISA bridge is already created as follows:
1> We set this ISA type explicitly; 2> We register that as 00:15.0.
In qemu-upstream, as you commented we can't create this as a ISA class type explicitly. So we compromise by faking this ISA bridge without ISA class type setting (as I recall you already said this way is slightly better). Maybe we will figure better way in the future. But anyway, this is always registered as 00:15.0, right? So I think the i915 driver can go back to probe the devfn like the native environment.
If I'm wrong please correct me.
Thanks Tiejun
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