This comments the less obvious portion of the code for setting up memory windows, and the platform dependency for initializing the h/w with appropriate resources. Signed-off-by: Keith Busch <keith.busch@xxxxxxxxx> --- arch/x86/pci/vmd.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/x86/pci/vmd.c b/arch/x86/pci/vmd.c index d57e480..68faa5e 100644 --- a/arch/x86/pci/vmd.c +++ b/arch/x86/pci/vmd.c @@ -532,6 +532,23 @@ static int vmd_enable_domain(struct vmd_dev *vmd) .flags = IORESOURCE_BUS | IORESOURCE_PCI_FIXED, }; + /* + * If the window is below 4GB, clear IORESOURCE_MEM_64 so we can + * put 32-bit resources in the window. + * + * There's no hardware reason why a 64-bit window *couldn't* + * contain a 32-bit resource, but pbus_size_mem() computes the + * bridge window size assuming a 64-bit window will contain no + * 32-bit resources. __pci_assign_resource() enforces that + * artificial restriction to make sure everything will fit. + * + * The only way we could use a 64-bit non-prefechable MEMBAR is + * if its address is <4GB so that we can convert it to a 32-bit + * resource. To be visible to the host OS, all VMD endpoints must + * be initially configured by platform BIOS, which includes setting + * up these resources. We can assume the device is configured + * according to the platform needs. + */ res = &vmd->dev->resource[VMD_MEMBAR1]; upper_bits = upper_32_bits(res->end); flags = res->flags & ~IORESOURCE_SIZEALIGN; -- 2.7.2 -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
