Background ========================================================================== Solve bug report: https://bugzilla.kernel.org/show_bug.cgi?id=203243 Currently, the kernel can sometimes assign the MMIO_PREF window additional size into the MMIO window, resulting in double the MMIO additional size, even if the MMIO_PREF window was successful. This happens if in the first pass, the MMIO_PREF succeeds but the MMIO fails. In the next pass, because MMIO_PREF is already assigned, the attempt to assign MMIO_PREF returns an error code instead of success (nothing more to do, already allocated). Example of problem (more context can be found in the bug report URL): Mainline kernel: pci 0000:06:01.0: BAR 14: assigned [mem 0x90100000-0xa00fffff] = 256M pci 0000:06:04.0: BAR 14: assigned [mem 0xa0200000-0xb01fffff] = 256M Patched kernel: pci 0000:06:01.0: BAR 14: assigned [mem 0x90100000-0x980fffff] = 128M pci 0000:06:04.0: BAR 14: assigned [mem 0x98200000-0xa01fffff] = 128M This was using pci=realloc,hpmemsize=128M,nocrs - on the same machine with the same configuration, with a Ubuntu mainline kernel and a kernel patched with this patch series. This patch is vital for the next patch in the series. The next patch allows the user to specify MMIO and MMIO_PREF independently. If the MMIO_PREF is set to be very large, this bug will end up more than doubling the MMIO size. The bug results in the MMIO_PREF being added to the MMIO window, which means doubling if MMIO_PREF size == MMIO size. With a large MMIO_PREF, without this patch, the MMIO window will likely fail to be assigned altogether due to lack of 32-bit address space. Patch notes ========================================================================== Change find_free_bus_resource() to not skip assigned resources with non-null parent. Add checks in pbus_size_io() and pbus_size_mem() to return success if resource returned from find_free_bus_resource() is already allocated. This avoids pbus_size_io() and pbus_size_mem() returning error code to __pci_bus_size_bridges() when a resource has been successfully assigned in a previous pass. This fixes the existing behaviour where space for a resource could be reserved multiple times in different parent bridge windows. This also greatly reduces the number of failed BAR messages in dmesg when Linux assigns resources. Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@xxxxxxxxxxxxxx> --- drivers/pci/setup-bus.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-) diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c index 5675254fa..8e1bc7ee7 100644 --- a/drivers/pci/setup-bus.c +++ b/drivers/pci/setup-bus.c @@ -752,13 +752,18 @@ static void pci_bridge_check_ranges(struct pci_bus *bus) } /* - * Helper function for sizing routines: find first available bus resource - * of a given type. Note: we intentionally skip the bus resources which - * have already been assigned (that is, have non-NULL parent resource). + * Helper function for sizing routines: find first bus resource of a given + * type. Note: we do not skip the bus resources which have already been + * assigned (r->parent != NULL). This is because a resource that is already + * assigned (nothing more to be done) will be indistinguishable from one that + * failed due to lack of space if we skip assigned resources. If the caller + * function cannot tell the difference then it might try to place the + * resources in a different window, doubling up on resources or causing + * unforeseeable issues. */ -static struct resource *find_free_bus_resource(struct pci_bus *bus, - unsigned long type_mask, - unsigned long type) +struct resource *find_bus_resource_of_type(struct pci_bus *bus, + unsigned long type_mask, + unsigned long type) { int i; struct resource *r; @@ -766,7 +771,7 @@ static struct resource *find_free_bus_resource(struct pci_bus *bus, pci_bus_for_each_resource(bus, r, i) { if (r == &ioport_resource || r == &iomem_resource) continue; - if (r && (r->flags & type_mask) == type && !r->parent) + if (r && (r->flags & type_mask) == type) return r; } return NULL; @@ -866,14 +871,16 @@ static void pbus_size_io(struct pci_bus *bus, resource_size_t min_size, struct list_head *realloc_head) { struct pci_dev *dev; - struct resource *b_res = find_free_bus_resource(bus, IORESOURCE_IO, - IORESOURCE_IO); + struct resource *b_res = find_bus_resource_of_type(bus, IORESOURCE_IO, + IORESOURCE_IO); resource_size_t size = 0, size0 = 0, size1 = 0; resource_size_t children_add_size = 0; resource_size_t min_align, align; if (!b_res) return; + if (b_res->parent) + return; min_align = window_alignment(bus, IORESOURCE_IO); list_for_each_entry(dev, &bus->devices, bus_list) { @@ -978,7 +985,7 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask, resource_size_t min_align, align, size, size0, size1; resource_size_t aligns[18]; /* Alignments from 1MB to 128GB */ int order, max_order; - struct resource *b_res = find_free_bus_resource(bus, + struct resource *b_res = find_bus_resource_of_type(bus, mask | IORESOURCE_PREFETCH, type); resource_size_t children_add_size = 0; resource_size_t children_add_align = 0; @@ -986,6 +993,8 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask, if (!b_res) return -ENOSPC; + if (b_res->parent) + return 0; memset(aligns, 0, sizeof(aligns)); max_order = 0; -- 2.20.1
