On Mon, Nov 25, 2013 at 6:28 PM, Yinghai Lu <yinghai@xxxxxxxxxx> wrote:
> Some x86 systems expose above 4G 64bit mmio in _CRS as non-pref mmio range.
> [ 49.415281] PCI host bridge to bus 0000:00
> [ 49.419921] pci_bus 0000:00: root bus resource [bus 00-1e]
> [ 49.426107] pci_bus 0000:00: root bus resource [io 0x0000-0x0cf7]
> [ 49.433041] pci_bus 0000:00: root bus resource [io 0x1000-0x5fff]
> [ 49.440010] pci_bus 0000:00: root bus resource [mem 0x000a0000-0x000bffff]
> [ 49.447768] pci_bus 0000:00: root bus resource [mem 0xfed8c000-0xfedfffff]
> [ 49.455532] pci_bus 0000:00: root bus resource [mem 0x90000000-0x9fffbfff]
> [ 49.463259] pci_bus 0000:00: root bus resource [mem 0x380000000000-0x381fffffffff]
>
> During assign unassigned 64bit mmio resource, it will go through
> every non-pref mmio for root bus in pci_bus_alloc_resource().
> As the loop is with pci_bus_for_each_resource(), and could have chance
> to use under 4G mmio range instead of above 4G mmio range if the requested
> range is not big enough, even it could handle above 4G 64bit pref mmio.
>
> For root bus, we can order list from high to low in pci_add_resource_offset(),
> during creating root bus, it will still keep the same order in final bus
> resource list.
> pci_acpi_scan_root
> ==> add_resources
> ==> pci_add_resource_offset: # Add to temp resources
> ==> pci_create_root_bus
> ==> pci_bus_add_resource # add to final bus resources.
>
> After that, we can make sure 64bit pref mmio for pci bridges will be allocated
> higest of mmio non-pref, and in this case it is above 4G instead of under 4G.
Sorry I'm so slow; I'd like to know what problem this solves, too.
I'm trying to help people at distros figure out whether they will need
to backport this change.
> Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
> ---
> drivers/pci/bus.c | 15 +++++++++++++--
> 1 file changed, 13 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/pci/bus.c b/drivers/pci/bus.c
> index f801f6a..adf17858 100644
> --- a/drivers/pci/bus.c
> +++ b/drivers/pci/bus.c
> @@ -21,7 +21,8 @@
> void pci_add_resource_offset(struct list_head *resources, struct resource *res,
> resource_size_t offset)
> {
> - struct pci_host_bridge_window *window;
> + struct pci_host_bridge_window *window, *tmp;
> + struct list_head *n;
>
> window = kzalloc(sizeof(struct pci_host_bridge_window), GFP_KERNEL);
> if (!window) {
> @@ -31,7 +32,17 @@ void pci_add_resource_offset(struct list_head *resources, struct resource *res,
>
> window->res = res;
> window->offset = offset;
> - list_add_tail(&window->list, resources);
> +
> + /* sorted it according to res end */
> + n = resources;
> + list_for_each_entry(tmp, resources, list)
> + if (window->res->end > tmp->res->end) {
> + n = &tmp->list;
> + break;
> + }
> +
> + /* Insert it just before n */
> + list_add_tail(&window->list, n);
> }
> EXPORT_SYMBOL(pci_add_resource_offset);
>
> --
> 1.8.1.4
>
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