On 2019-11-13 8:25 a.m., 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> You can add mine as well: Reviewed-by: Logan Gunthorpe <logang@xxxxxxxxxxxx> Thanks, Logan
