On Tue, May 01, 2018 at 03:32:46PM -0500, Bjorn Helgaas wrote:
> This is where it gets hard for me -- I'm not really comfortable if we
> have to convince ourselves that code is correct by testing every
> scenario. It's a lot better if we can convince ourselves by reasoning
> about what the code does. That's not very reliable either, but if we
> understand the code, we at least have a hope of being able to fix the
> bugs we missed in our reasoning.
I took another look at the code and we can calculate everything upfront
before resources get distributed to hotplug bridges. I also tried and it
still works on my test systems. Does the below patch look more
acceptable to you?
diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c
index 072784f55ea5..cbc80dd5e8d8 100644
--- a/drivers/pci/setup-bus.c
+++ b/drivers/pci/setup-bus.c
@@ -1881,6 +1881,7 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus,
unsigned int normal_bridges = 0, hotplug_bridges = 0;
struct resource *io_res, *mmio_res, *mmio_pref_res;
struct pci_dev *dev, *bridge = bus->self;
+ resource_size_t align, io_align, mem_align;
io_res = &bridge->resource[PCI_BRIDGE_RESOURCES + 0];
mmio_res = &bridge->resource[PCI_BRIDGE_RESOURCES + 1];
@@ -1919,27 +1920,43 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus,
normal_bridges++;
}
+ io_align = window_alignment(bus, IORESOURCE_IO);
+ mem_align = window_alignment(bus, IORESOURCE_MEM);
+
for_each_pci_bridge(dev, bus) {
- const struct resource *res;
+ struct resource *res;
if (dev->is_hotplug_bridge)
continue;
/*
* Reduce the available resource space by what the
- * bridge and devices below it occupy.
+ * bridge and devices below it occupy taking into
+ * account alignment if it differs from the default.
*/
res = &dev->resource[PCI_BRIDGE_RESOURCES + 0];
- if (!res->parent && available_io > resource_size(res))
+ if (!res->parent && available_io > resource_size(res)) {
remaining_io -= resource_size(res);
+ align = pci_resource_alignment(dev, res);
+ if (align > io_align)
+ remaining_io -= align - io_align;
+ }
res = &dev->resource[PCI_BRIDGE_RESOURCES + 1];
- if (!res->parent && available_mmio > resource_size(res))
+ if (!res->parent && available_mmio > resource_size(res)) {
remaining_mmio -= resource_size(res);
+ align = pci_resource_alignment(dev, res);
+ if (align > mem_align)
+ remaining_mmio -= align - mem_align;
+ }
res = &dev->resource[PCI_BRIDGE_RESOURCES + 2];
- if (!res->parent && available_mmio_pref > resource_size(res))
+ if (!res->parent && available_mmio_pref > resource_size(res)) {
remaining_mmio_pref -= resource_size(res);
+ align = pci_resource_alignment(dev, res);
+ if (align > mem_align)
+ remaining_mmio_pref -= align - mem_align;
+ }
}
/*
@@ -1964,7 +1981,7 @@ static void pci_bus_distribute_available_resources(struct pci_bus *bus,
available_io, available_mmio,
available_mmio_pref);
} else if (dev->is_hotplug_bridge) {
- resource_size_t align, io, mmio, mmio_pref;
+ resource_size_t io, mmio, mmio_pref;
/*
* Distribute available extra resources equally
--
2.17.0
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