From: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> mainline inclusion from mainline-v7.0-rc1 commit f909e3ee3ed1a44202f09ac7e637a0f9ec372225 category: bugfix bugzilla: 190863 Reference: https://web.git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/... -------------------------------- calculate_memsize() applies lower bound to the resource size before aligning the resource size making it impossible to shrink bridge window resources. I've not found any justification for this lower bound and nothing indicated it was to work around some HW issue. Prior to the commit 3baeae36039a ("PCI: Use pci_release_resource() instead of release_resource()"), releasing a bridge window during BAR resize resulted in clearing start and end address of the resource. Clearing addresses destroys the resource size as a side-effect, therefore nullifying the effect of the old size lower bound. After the commit 3baeae36039a ("PCI: Use pci_release_resource() instead of release_resource()"), BAR resize uses the aligned old size, which results in exceeding what fits into the parent window in some cases: xe 0030:03:00.0: [drm] Attempting to resize bar from 256MiB -> 16384MiB xe 0030:03:00.0: BAR 0 [mem 0x620c000000000-0x620c000ffffff 64bit]: releasing xe 0030:03:00.0: BAR 2 [mem 0x6200000000000-0x620000fffffff 64bit pref]: releasing pci 0030:02:01.0: bridge window [mem 0x6200000000000-0x620001fffffff 64bit pref]: releasing pci 0030:01:00.0: bridge window [mem 0x6200000000000-0x6203fbff0ffff 64bit pref]: releasing pci 0030:00:00.0: bridge window [mem 0x6200000000000-0x6203fbff0ffff 64bit pref]: was not released (still contains assigned resources) pci 0030:00:00.0: Assigned bridge window [mem 0x6200000000000-0x6203fbff0ffff 64bit pref] to [bus 01-04] free space at [mem 0x6200400000000-0x62007ffffffff 64bit pref] pci 0030:00:00.0: Assigned bridge window [mem 0x6200000000000-0x6203fbff0ffff 64bit pref] to [bus 01-04] cannot fit 0x4000000000 required for 0030:01:00.0 bridging to [bus 02-04] The old size of 0x6200000000000-0x6203fbff0ffff resource was used as the lower bound which results in 0x4000000000 size request due to alignment. That exceeds what can fit into the parent window. Since the lower bound never even was enforced fully because the resource addresses were cleared when the bridge window is released, remove the old_size lower bound entirely and trust the calculated bridge window size is enough. This same problem may occur on io window side but seems less likely to cause issues due to general difference in alignment. Removing the lower bound may have other unforeseen consequences in case of io window so it's better to leave it as -next material if no problem is reported related to io window sizing (BAR resize shouldn't touch io windows anyway). Fixes: 3baeae36039a ("PCI: Use pci_release_resource() instead of release_resource()") Reported-by: Simon Richter <Simon.Richter@hogyros.de> Link: https://lore.kernel.org/r/f9a8c975-f5d3-4dd2-988e-4371a1433a60@hogyros.de/ Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@linux.intel.com> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Link: https://patch.msgid.link/20251219174036.16738-6-ilpo.jarvinen@linux.intel.co... Conflicts: drivers/pci/setup-bus.c [conflicts due to not mergered prerequisites] Signed-off-by: Zhang Hongtao <zhanghongtao35@huawei.com> --- drivers/pci/setup-bus.c | 10 ++-------- 1 file changed, 2 insertions(+), 8 deletions(-) diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c index 39d19302f3cbe..fe6f68d9e465b 100644 --- a/drivers/pci/setup-bus.c +++ b/drivers/pci/setup-bus.c @@ -794,15 +794,10 @@ static resource_size_t calculate_iosize(resource_size_t size, static resource_size_t calculate_memsize(resource_size_t size, resource_size_t min_size, resource_size_t size1, - resource_size_t old_size, resource_size_t align) { if (size < min_size) size = min_size; - if (old_size == 1) - old_size = 0; - if (size < old_size) - size = old_size; size = ALIGN(size + size1, align); return size; } @@ -1041,13 +1036,12 @@ static int pbus_size_mem(struct pci_bus *bus, unsigned long mask, min_align = calculate_mem_align(aligns, max_order); min_align = max(min_align, window_alignment(bus, b_res->flags)); - size0 = calculate_memsize(size, min_size, 0, resource_size(b_res), min_align); + size0 = calculate_memsize(size, min_size, 0, min_align); add_align = max(min_align, add_align); if (children_add_size > add_size) add_size = children_add_size; size1 = (!realloc_head || (realloc_head && !add_size)) ? size0 : - calculate_memsize(size, min_size, add_size, - resource_size(b_res), add_align); + calculate_memsize(size, min_size, add_size, add_align); if (!size0 && !size1) { if (b_res->start || b_res->end) pci_info(bus->self, "disabling bridge window %pR to %pR (unused)\n", -- 2.43.0