On Tue, Nov 12, 2019 at 11:39:53AM +0200, mika.westerberg@xxxxxxxxxxxxxxx wrote: > 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> Thanks for reviewing. > > 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; Well, technically "r" is used before "i", although "r_assigned" is after "i", so I could change it, but it was not in reverse tree order, and I tend to leave things as they are. I will consider it. > > > > > 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). Something like /* If resource is already assigned, nothing more to do. */ OR /* If resource is already assigned (->parent != NULL), nothing more to do */ OR something else? > > > + 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. Same as above, will use the same comment if I do one. > > > + if (b_res->parent) > > + return 0; > > > > memset(aligns, 0, sizeof(aligns)); > > max_order = 0; > > -- > > 2.23.0 Thanks, Kind regards, Nicholas
