[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] intel IGD driver intel_detect_pch() failure
On Tue, Dec 11, 2012 at 8:01 PM, Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx> wrote: > > On Tue, 11 Dec 2012, G.R. wrote: > > > > On Tue, Dec 11, 2012 at 2:15 AM, Kay, Allen M <allen.m.kay@xxxxxxxxx> wrote: > > My understanding is that i915 driver needs to looks at the real PCH's device ID to apply HW workarounds. > > > > One way to fix this is to make the device ID of the first PCH's (00:01.0) device ID reflect the device ID of > > 00:1f.0 on the host. This way, when i915 running as a guest will find the valid PCH device ID to make workaround > > decisions with. > > > > > > I don't know why it would make a difference if i915 is built into the kernel or as a module though. > > > > Allen > > > > Thanks Allen for your input. > > But module v.s. built-in is not the only difference. Another difference is the PVHVM build vs. pure HVM build. > > Both share the same PCI layout but different result. Any theory how to explain the difference? What makes the PVHVM version > > work? > > Please don't use HTML in emails. > I'm using gmail and not sure how to control html formatting. I explicitly use 'remove formatting' this time, does it look better now? Sorry for the inconvenience. > > PVHVM Linux guests setup interrupts differently: they request an event > channel for each legacy interrupt or MSI/MSI-X, then the hypervisor uses > these event channels to inject notifications into the guest, rather > than emulated interrupts or emulated MSIs. > Will this affect the result of pci_get_class() as called by the intel driver? If not, this can still not explain the different behavior. Maybe I need to do one more experiment when I got time. > > Reading again the description of the bug, wouldn't it be better to just > the fix the problem in Linux? > In fact this looks like a bug in intel_detect_pch(): QEMU is emulating a > PCI-PCI bridge and the driver is checking for an PCI-ISA bridge (to help > with virtualization?). Moreover it only checks the first PCI-ISA bridge. > > As far as I know Xen has never exposed a PCI-ISA bridge with vendor == > Intel to the guest. > But why do xen expose the PCI-ISA bridge in host as a PCI-PCI bridge, doesn't it sounds strange? _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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