[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] intel IGD driver intel_detect_pch() failure
CC'ing some engineers that could have some useful suggestions On Mon, 10 Dec 2012, G.R. wrote: > Hello, could anybody help? > > On Sun, Dec 9, 2012 at 1:00 PM, G.R. <firemeteor@xxxxxxxxxxxxxxxxxxxxx> wrote: > I dug further and got confused. > The host ISA bridge 00:1f.0 is automatically passed-through as part of > the gfx_passthru magic. > However, it is passed through as a PCI bridge: > On host:  00:1f.0 ISA bridge [0601]: Intel Corporation H77 Express > Chipset LPC Controller [8086:1e4a] (rev 04) > On guest: 00:1f.0 PCI bridge [0604]: Intel Corporation H77 Express > Chipset LPC Controller [8086:1e4a] (rev 04) > > This is both the case for pure HVM && PVHVM. And this one exists for > both case too: > 00:01.0 ISA bridge [0601]: Intel Corporation 82371SB PIIX3 ISA > [Natoma/Triton II] [8086:7000] > > And the intel_detect_pch() function only check the first ISA bridge on > the PCI bus: > pch = pci_get_class(PCI_CLASS_BRIDGE_ISA << 8, NULL); > > Unless there are magic elsewhere, I can't imagine the code would behave > differently on the two builds. > But what's the magic behind this? > > Also, is there anyway to get rid of the ISA bridge emulated by qemu? > I don't think this is ever required for most case... > > Thanks, > Timothy > > > On Sun, Dec 9, 2012 at 1:43 AM, G.R. <firemeteor@xxxxxxxxxxxxxxxxxxxxx> > wrote: > > Hi all, > I'm debugging an issue that an HVM guest failed to produce any > output with IGD passed through. > This is an pure HVM linux guest with i915 driver directly > compiled in. > An PVHVM kernel with i915 driver compiled as module works without > issue. > I'm not yet sure which factor is more important, pure HVM or the > I915=y kernel config. > > The direct cause of no output is that the driver does not select > Display PLL properly, which is in turn > due to fail to detect pch type properly. > > Strange enough, the intel_detect_pch() function works by checking > the device ID of the ISA bridge > coming with the chipset: > > /* * The reason to probe ISA bridge instead of Dev31:Fun0 is to * > make graphics device passthrough > fwork easy for VMM, that only * need to expose ISA bridge to let > driver know the real hardware > underneath. This is a requirement from virtualization team. */ > > I added some debug output in this function and find out that it > obtained a strange device ID: > [ 1.005423] [drm] intel pch detect, found 00007000 > > This looks like the ISA bridge provided by qemu: > 00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA > [Natoma/Triton II] > 00:01.0 0601: 8086:7000 > > However, I can find the same device on a PVHVM linux guest, but > the intel_detect_pch() is not fooled by > that. Is it due to I915=m config or some magic played by PVOPS? > Any suggestion how to fix this? > > Thanks, > Timothy > > > > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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