Re: [PATCH] radeon: Test for PCI root bus before assuming bus->self

From: Dave Airlie
Date: Wed Aug 27 2014 - 21:33:06 EST

> On Wed, Aug 27, 2014 at 3:01 PM, Alex Williamson
> <alex.williamson@xxxxxxxxxx> wrote:
>> If we assign a Radeon device to a virtual machine, we can no longer
>> assume a fixed hardware topology, like the GPU having a parent device.
>> This patch simply adds a few pci_is_root_bus() tests to avoid passing
>> a NULL pointer to PCI access functions, allowing the radeon driver to
>> work in a QEMU 440FX machine with an assigned HD8570 on the emulated
>> PCI root bus.
>> Signed-off-by: Alex Williamson <alex.williamson@xxxxxxxxxx>

Does this mean inside a VM we can't enable pcie 2 speeds?

This could lead to a quite disappointing speed decrease for DMA transfers.

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