On Thu, Nov 07, 2019 at 01:50:57PM +0000, Nicholas Johnson wrote: > Currently, the kernel can sometimes assign the MMIO_PREF window > additional size into the MMIO window, resulting in extra MMIO additional > size, despite the MMIO_PREF additional size being assigned successfully > into the MMIO_PREF window. > > 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). Hence, the size which is > actually allocated, but thought to have failed, is placed in the MMIO > window. > > 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. > > 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, > the MMIO window will likely fail to be assigned altogether due to lack > of 32-bit address space. > > Change find_free_bus_resource() to do the following: > - Return first unassigned resource of the correct type. > - If none of the above, return first assigned resource of the correct type. > - If none of the above, return NULL. > > Returning an assigned resource of the correct type allows the caller to > distinguish between already assigned and no resource of the correct type. > > Rename find_free_bus_resource to find_bus_resource_of_type(). > > 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. > > Link: https://lore.kernel.org/lkml/20190531171216.20532-2-logang@xxxxxxxxxxxx/T/#u > Link: https://bugzilla.kernel.org/show_bug.cgi?id=203243 > > Reported-by: Kit Chow <kchow@xxxxxxxxxx> > Reported-by: Nicholas Johnson <nicholas.johnson-opensource@xxxxxxxxxxxxxx> > Signed-off-by: Nicholas Johnson <nicholas.johnson-opensource@xxxxxxxxxxxxxx> Reviewed-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx> Minor nits below. > --- > drivers/pci/setup-bus.c | 34 +++++++++++++++++++++++----------- > 1 file changed, 23 insertions(+), 11 deletions(-) > > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c > index e7dbe2170..f97c36a1e 100644 > --- a/drivers/pci/setup-bus.c > +++ b/drivers/pci/setup-bus.c > @@ -752,24 +752,32 @@ 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. > + * Assigned resources have non-NULL parent resource. > + * > + * Return first unassigned resource of the correct type. > + * If none of the above, return first assigned resource of the correct type. > + * If none of the above, return NULL. > + * > + * Returning an assigned resource of the correct type allows the caller to > + * distinguish between already assigned and no resource of the correct type. > */ > -static struct resource *find_free_bus_resource(struct pci_bus *bus, > - unsigned long type_mask, > - unsigned long type) > +static struct resource *find_bus_resource_of_type(struct pci_bus *bus, > + unsigned long type_mask, > + unsigned long type) > { > int i; > - struct resource *r; > + struct resource *r, *r_assigned = NULL; Maybe order them struct resource *r, *r_assigned = NULL; int i; > > 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) > return r; > + if (r && (r->flags & type_mask) == type && !r_assigned) > + r_assigned = r; > } > - return NULL; > + return r_assigned; > } > > static resource_size_t calculate_iosize(resource_size_t size, > @@ -866,14 +874,16 @@ 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; I think it may be good to comment here that skip the resources that are assigned (->parent != NULL). > + if (b_res->parent) > + return; > > min_align = window_alignment(bus, IORESOURCE_IO); > list_for_each_entry(dev, &bus->devices, bus_list) { > @@ -978,7 +988,7 @@ 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 +996,8 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask, > > if (!b_res) > return -ENOSPC; Ditto. > + if (b_res->parent) > + return 0; > > memset(aligns, 0, sizeof(aligns)); > max_order = 0; > -- > 2.23.0
