From: Jake Oshins <jakeo@xxxxxxxxxxxxx> Hyper-V VMs expose paravirtual drivers through a mechanism called VMBus, which is managed by hv_vmbus.ko. For each paravirtual service instance, this driver exposes a new child device. Some of these child devices need memory address space, into which Hyper-V will map things like the virtual video framebuffer. This memory-mapped address space is chosen by the guest OS, not the hypervisor. This is difficult to map onto the Linux pnp layer, as the code in the pnp layer to choose MMIO space keys off of bus type and it doesn't know anything about VMBus. The maintainers of the pnp layer have asked that we not offer patches to it that make it understand VMBus, but that we rather find ways of using the code in its current state. So hv_vmbus.ko exports a function, vmbus_allocate_mmio() for choosing the address space for any child driver that needs this facility. The recently introduced PCI front-end driver for Hyper-V VMs (pci-hyperv.ko) uses vmbus_allocate_mmio() for choosing both the region of memory into which PCI configuration space can be mapped and the region of memory into which real PCI Express devices which are passed through to the VM should occupy. The regions allocated are made to look like root PCI bus bridge windows to the PCI driver, reusing all the code in the PCI driver for the rest of the PCI device management. The problem is that these bridge windows are marked in such a way that devices can still allocate from the memory space spanned by them, and this means that if two different PCI buses are created in the VM, each with devices under them, they may allocate the same memory space, leading to PCI Base Address Registers which overlap. This patch series fixes the problem by tracking allocations to child devices in a separate resource tree, marking them such that the bridge windows can't overlap. The main memory resource tree, iomem_resource, contains resources properly marked as bridge windows, allowing their children to overlap with them. Jake Oshins (5): hv: Make a function to free mmio regions through vmbus hv: Lock access to hyperv_mmio resource tree hv: Use new vmbus_mmio_free() from client drivers. hv: Reverse order of resources in hyperv_mmio hv: Track allocations of children of hv_vmbus in private resource tree drivers/hv/vmbus_drv.c | 56 +++++++++++++++++++++++++++++++++++------ drivers/pci/host/pci-hyperv.c | 14 +++++------ drivers/video/fbdev/hyperv_fb.c | 4 +-- include/linux/hyperv.h | 2 +- 4 files changed, 59 insertions(+), 17 deletions(-) -- 1.9.1 -- 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
