On Fri, 22 Aug 2025, Ilpo Järvinen wrote: > This series is based on top of the three resource fitting and > assignment algorithm fixes (v3).
I realized I didn't include a link to those patches. It's this series: https://lore.kernel.org/linux-pci/20250822123359.16305-1-ilpo.jarvi...@linux.intel.com/ I'm sorry about the extra hassle. -- i. > PCI resource fitting and assignment code needs to find the bridge > window a resource belongs to in multiple places, yet, no common > function for that exists. Thus, each site has its own version of > the decision, each with their own corner cases, misbehaviors, and > some resulting in complex interfaces between internal functions. > > This series tries to rectify the situation by adding two new functions > to select the bridge window. To support these functions, bridge windows > must always contain their type information in flags which requires > modifying the flags behavior for bridge window resources. > > I've hit problems related to zeroed resource flags so many times by now > that I've already lost count which has highlighted over and over again > that clearing type information is not a good idea. As also proven by > some changes of this series, retaining the flags for bridge windows > ended up fixing existing issues (although kernel ended up recovering > from the worst problem graciously and the other just results in dormant > code). > > This series only changes resource flags behavior for bridge windows. > The sensible direction is to make a similar change for the other > resources as well eventually but making that change involves more > uncertainty and is not strictly necessary yet. Driver code outside of > PCI core could have assumptions about the flags, whereas bridge windows > are mostly internal to PCI core code (or should be, sane endpoint > drivers shouldn't be messing with the bridge windows). Thus, limiting > the flags behavior changes to bridge windows for now is safer than > attempting full behavioral change in a single step. > > > I've tried to look out for any trouble that code under arch/ could > cause after the flags start to behave differently and therefore ended > up consolidating arch/ code to use pci_enable_resources(). My > impression is that strictly speaking only the MIPS code would break > similar to PCI core's copy of pci_enable_resources(), the others were > much more lax in checking so they'd likely keep working but > consolidation seemed still the best approach there as the enable checks > seemed diverging for no apparent reason. > > Most sites are converted by this change. There are three known places > that are not yet converted: > > - fail_type based logic in __assign_resources_sorted(): > I'm expecting to cover this along with the resizable BAR > changes as I need to change the fallback logic anyway (one > of the motivators what got me started with this series, > I need an easy way to acquire the bridge window during > retries/fallbacks if maximum sized BARs do not fit, which > is what this series provides). > > - Failure detection after BAR resize: Keeps using the type > based heuristic for failure detection. It isn't very clear how > to decide which assignment failures should be counted and which > not. There could be pre-existing failures that keep happening > that end up blocking BAR resize but that's no worse than behavior > before this series. How to identify the relevant failures does > not look straightforward given the current structures. This > clearly needs more thought before coding any solution. > > - resource assignment itself: This is a very complex change > due to bus and kernel resources abstractions and might not be > realistic any time soon. > > I'd have wanted to also get rid of pci_bridge_check_ranges() that > (re)adds type information which seemed now unnecessary. It turns out, > however, that root windows still require so it will have to wait for > now. > > This change has been tested on a large number of machine I've access to > which come with heterogeneous PCI configurations. Some resources > retained their original addresses now also with pci=realloc because > this series fixed the unnecessary release(+assign) of those resources. > Other than that, nothing worth of note from that testing. > > > My test coverage is x86 centric unfortunately so I'd appreciate if > somebody with access to non-x86 archs takes the effort to test this > series. > > Info for potential testers: > > Usually, it's enough to gather lspci -vvv pre and post the series, and > use diff to see whether the resources remained the same and also check > that the same drivers are still bound to the devices to confirm that > devices got properly enabled (also shown by lspci -vvv). I normally > test both with and without pci=realloc. In case of a trouble, besides > lspci -vvv output, providing pre and post dmesg and /proc/iomem > contents would be helpful, please take the dmesg with dyndbg="file > drivers/pci/*.c +p" on the kernel cmdline. > > Ilpo Järvinen (24): > m68k/PCI: Use pci_enable_resources() in pcibios_enable_device() > sparc/PCI: Remove pcibios_enable_device() as they do nothing extra > MIPS: PCI: Use pci_enable_resources() > PCI: Move find_bus_resource_of_type() earlier > PCI: Refactor find_bus_resource_of_type() logic checks > PCI: Always claim bridge window before its setup > PCI: Disable non-claimed bridge window > PCI: Use pci_release_resource() instead of release_resource() > PCI: Enable bridge even if bridge window fails to assign > PCI: Preserve bridge window resource type flags > PCI: Add defines for bridge window indexing > PCI: Add bridge window selection functions > PCI: Fix finding bridge window in pci_reassign_bridge_resources() > PCI: Warn if bridge window cannot be released when resizing BAR > PCI: Use pbus_select_window() during BAR resize > PCI: Use pbus_select_window_for_type() during IO window sizing > PCI: Rename resource variable from r to res > PCI: Use pbus_select_window() in space available checker > PCI: Use pbus_select_window_for_type() during mem window sizing > PCI: Refactor distributing available memory to use loops > PCI: Refactor remove_dev_resources() to use pbus_select_window() > PCI: Add pci_setup_one_bridge_window() > PCI: Pass bridge window to pci_bus_release_bridge_resources() > PCI: Alter misleading recursion to pci_bus_release_bridge_resources() > > arch/m68k/kernel/pcibios.c | 39 +- > arch/mips/pci/pci-legacy.c | 38 +- > arch/sparc/kernel/leon_pci.c | 27 -- > arch/sparc/kernel/pci.c | 27 -- > arch/sparc/kernel/pcic.c | 27 -- > drivers/pci/bus.c | 3 + > drivers/pci/pci-sysfs.c | 27 +- > drivers/pci/pci.h | 8 +- > drivers/pci/probe.c | 35 +- > drivers/pci/setup-bus.c | 798 ++++++++++++++++++----------------- > drivers/pci/setup-res.c | 46 +- > include/linux/pci.h | 5 +- > 12 files changed, 504 insertions(+), 576 deletions(-) > > > base-commit: 8f5ae30d69d7543eee0d70083daf4de8fe15d585 > prerequisite-patch-id: 801e8dd3aa9847d4945cb7d8958574a6006004ab > prerequisite-patch-id: 0233311f04e3ea013676b6cc00626410bbe11e41 > prerequisite-patch-id: 9841faf37d56c1acf1167559613e862ef62e509d >
