kernel/linux.git/include/linux/pci_hotplug.h, branch v6.6.132

PCI: Change the type of probe argument in reset functions

2021-08-18T22:32:42+00:00

Change the type of probe argument in functions which implement reset methods from int to bool to make the context and intent clear. Suggested-by: Alex Williamson Link: https://lore.kernel.org/r/20210817180500.1253-10-ameynarkhede03@gmail.com Signed-off-by: Amey Narkhede Signed-off-by: Bjorn Helgaas

PCI: Fix kernel-doc formatting

2021-07-06T15:37:46+00:00

Fix kernel-doc formatting throughout drivers/pci and related include files. No change to functionality intended. Check for warnings: $ find include drivers/pci -type f -path "*pci*.[ch]" | xargs scripts/kernel-doc -none [bhelgaas: squashed to one commit] Link: https://lore.kernel.org/r/20210509030237.368540-1-kw@linux.com Link: https://lore.kernel.org/r/20210703151306.1922450-1-kw@linux.com Link: https://lore.kernel.org/r/20210703151306.1922450-2-kw@linux.com Link: https://lore.kernel.org/r/20210703151306.1922450-3-kw@linux.com Link: https://lore.kernel.org/r/20210703151306.1922450-4-kw@linux.com Link: https://lore.kernel.org/r/20210703151306.1922450-5-kw@linux.com Signed-off-by: Krzysztof Wilczyński Signed-off-by: Bjorn Helgaas

PCI/ACPI: Move _HPP & _HPX functions to pci-acpi.c

2019-08-28T20:25:53+00:00

Move program_hpx_type0(), program_hpx_type1(), etc., and enums hpx_type3_dev_type, hpx_type3_fn_type and hpx_type3_cfg_loc to drivers/pci/pci-acpi.c as these functions and enums are ACPI-specific. Move structs hpx_type0, hpx_type1, hpx_type2 and hpx_type3 to drivers/pci/pci.h as these are shared between drivers/pci/pci-acpi.c and drivers/pci/probe.c. Link: https://lore.kernel.org/r/20190827094951.10613-3-kw@linux.com Signed-off-by: Krzysztof Wilczynski Signed-off-by: Bjorn Helgaas

PCI/ACPI: Rename _HPX structs from hpp_* to hpx_*

2019-08-28T20:09:45+00:00

The names of the hpp_type0, hpp_type1 and hpp_type2 structs suggest that they're related to _HPP, when in fact they're related to _HPX. The struct hpp_type0 denotes an _HPX Type 0 setting record that supersedes the _HPP setting record, and it has been used interchangeably for _HPP as per the ACPI specification (see version 6.3, section 6.2.9.1) which states that it should be applied to PCI, PCI-X and PCI Express devices, with settings being ignored if they are not applicable. Rename them to hpx_type0, hpx_type1 and hpx_type2 to reflect their relation to _HPX rather than _HPP. Link: https://lore.kernel.org/r/20190827094951.10613-2-kw@linux.com Signed-off-by: Krzysztof Wilczynski Signed-off-by: Bjorn Helgaas

PCI/ACPI: Implement _HPX Type 3 Setting Record

2019-04-23T21:38:09+00:00

The _HPX Type 3 Setting Record is intended to be more generic and allow configuration of settings not possible with Type 2 records. For example, firmware could ensure that the completion timeout value is set accordingly throughout the PCI tree. Implement support for _HPX Type 3 Setting Records, which were added in the ACPI 6.3 spec. Link: https://lore.kernel.org/lkml/20190208162414.3996-4-mr.nuke.me@gmail.com Signed-off-by: Alexandru Gagniuc Signed-off-by: Bjorn Helgaas

PCI/ACPI: Remove the need for 'struct hotplug_params'

2019-04-23T21:38:05+00:00

We used to first parse all the _HPP and _HPX tables before using the information to program registers of PCIe devices. Up through HPX Type 2, there was only one structure of each type, so we could cheat and store it on the stack. With HPX Type 3 we get an arbitrary number of entries, so the above model doesn't scale that well. Instead of parsing all tables at once, parse and program each entry separately. For _HPP and _HPX Types 0 through 2, this is functionally equivalent. The change enables the upcoming _HPX Type 3 to integrate more easily. Link: https://lore.kernel.org/lkml/20190208162414.3996-3-mr.nuke.me@gmail.com Signed-off-by: Alexandru Gagniuc [bhelgaas: fix build errors] Signed-off-by: Bjorn Helgaas

PCI: hotplug: Embed hotplug_slot

2018-09-18T22:52:15+00:00

When the PCI hotplug core and its first user, cpqphp, were introduced in February 2002 with historic commit a8a2069f432c, cpqphp allocated a slot struct for its internal use plus a hotplug_slot struct to be registered with the hotplug core and linked the two with pointers: https://git.kernel.org/tglx/history/c/a8a2069f432c Nowadays, the predominant pattern in the tree is to embed ("subclass") such structures in one another and cast to the containing struct with container_of(). But it wasn't until July 2002 that container_of() was introduced with historic commit ec4f214232cf: https://git.kernel.org/tglx/history/c/ec4f214232cf pnv_php, introduced in 2016, did the right thing and embedded struct hotplug_slot in its internal struct pnv_php_slot, but all other drivers cargo-culted cpqphp's design and linked separate structs with pointers. Embedding structs is preferrable to linking them with pointers because it requires fewer allocations, thereby reducing overhead and simplifying error paths. Casting an embedded struct to the containing struct becomes a cheap subtraction rather than a dereference. And having fewer pointers reduces the risk of them pointing nowhere either accidentally or due to an attack. Convert all drivers to embed struct hotplug_slot in their internal slot struct. The "private" pointer in struct hotplug_slot thereby becomes unused, so drop it. Signed-off-by: Lukas Wunner Signed-off-by: Bjorn Helgaas Reviewed-by: Rafael J. Wysocki Acked-by: Tyrel Datwyler # drivers/pci/hotplug/rpa* Acked-by: Sebastian Ott # drivers/pci/hotplug/s390* Acked-by: Andy Shevchenko # drivers/platform/x86 Cc: Len Brown Cc: Scott Murray Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Oliver OHalloran Cc: Gavin Shan Cc: Gerald Schaefer Cc: Corentin Chary Cc: Darren Hart

PCI: hotplug: Drop hotplug_slot_info

2018-09-18T22:52:15+00:00

Ever since the PCI hotplug core was introduced in 2002, drivers had to allocate and register a struct hotplug_slot_info for every slot: https://git.kernel.org/tglx/history/c/a8a2069f432c Apparently the idea was that drivers furnish the hotplug core with an up-to-date card presence status, power status, latch status and attention indicator status as well as notify the hotplug core of changes thereof. However only 4 out of 12 hotplug drivers bother to notify the hotplug core with pci_hp_change_slot_info() and the hotplug core never made any use of the information: There is just a single macro in pci_hotplug_core.c, GET_STATUS(), which uses the hotplug_slot_info if the driver lacks the corresponding callback in hotplug_slot_ops. The macro is called when the user reads the attribute via sysfs. Now, if the callback isn't defined, the attribute isn't exposed in sysfs in the first place (see e.g. has_power_file()). There are only two situations when the hotplug_slot_info would actually be accessed: * If the driver defines ->enable_slot or ->disable_slot but not ->get_power_status. * If the driver defines ->set_attention_status but not ->get_attention_status. There is no driver doing the former and just a single driver doing the latter, namely pnv_php.c. Amend it with a ->get_attention_status callback. With that, the hotplug_slot_info becomes completely unused by the PCI hotplug core. But a few drivers use it internally as a cache: cpcihp uses it to cache the latch_status and adapter_status. cpqhp uses it to cache the adapter_status. pnv_php and rpaphp use it to cache the attention_status. shpchp uses it to cache all four values. Amend these drivers to cache the information in their private slot struct. shpchp's slot struct already contains members to cache the power_status and adapter_status, so additional members are only needed for the other two values. In the case of cpqphp, the cached value is only accessed in a single place, so instead of caching it, read the current value from the hardware. Caution: acpiphp, cpci, cpqhp, shpchp, asus-wmi and eeepc-laptop populate the hotplug_slot_info with initial values on probe. That code is herewith removed. There is a theoretical chance that the code has side effects without which the driver fails to function, e.g. if the ACPI method to read the adapter status needs to be executed at least once on probe. That seems unlikely to me, still maintainers should review the changes carefully for this possibility. Rafael adds: "I'm not aware of any case in which it will break anything, [...] but if that happens, it may be necessary to add the execution of the control methods in question directly to the initialization part." Signed-off-by: Lukas Wunner Signed-off-by: Bjorn Helgaas Reviewed-by: Rafael J. Wysocki Acked-by: Tyrel Datwyler # drivers/pci/hotplug/rpa* Acked-by: Sebastian Ott # drivers/pci/hotplug/s390* Acked-by: Andy Shevchenko # drivers/platform/x86 Cc: Len Brown Cc: Scott Murray Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Oliver OHalloran Cc: Gavin Shan Cc: Gerald Schaefer Cc: Corentin Chary Cc: Darren Hart

PCI: hotplug: Constify hotplug_slot_ops

2018-09-18T22:52:15+00:00

Hotplug drivers cannot declare their hotplug_slot_ops const, making them attractive targets for attackers, because upon registration of a hotplug slot, __pci_hp_initialize() writes to the "owner" and "mod_name" members in that struct. Fix by moving these members to struct hotplug_slot and constify every driver's hotplug_slot_ops except for pciehp. pciehp constructs its hotplug_slot_ops at runtime based on the PCIe port's capabilities, hence cannot declare them const. It can be converted to __write_rarely once that's mainlined: http://www.openwall.com/lists/kernel-hardening/2016/11/16/3 Signed-off-by: Lukas Wunner Signed-off-by: Bjorn Helgaas Reviewed-by: Rafael J. Wysocki Acked-by: Tyrel Datwyler # drivers/pci/hotplug/rpa* Acked-by: Andy Shevchenko # drivers/platform/x86 Cc: Len Brown Cc: Scott Murray Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Oliver OHalloran Cc: Gavin Shan Cc: Sebastian Ott Cc: Gerald Schaefer Cc: Corentin Chary Cc: Darren Hart

PCI: hotplug: Demidlayer registration with the core

2018-07-23T22:04:13+00:00

When a hotplug driver calls pci_hp_register(), all steps necessary for registration are carried out in one go, including creation of a kobject and addition to sysfs. That's a problem for pciehp once it's converted to enable/disable the slot exclusively from the IRQ thread: The thread needs to be spawned after creation of the kobject (because it uses the kobject's name), but before addition to sysfs (because it will handle enable/disable requests submitted via sysfs). pci_hp_deregister() does offer a ->release callback that's invoked after deletion from sysfs and before destruction of the kobject. But because pci_hp_register() doesn't offer a counterpart, hotplug drivers' ->probe and ->remove code becomes asymmetric, which is error prone as recently discovered use-after-free bugs in pciehp's ->remove hook have shown. In a sense, this appears to be a case of the midlayer antipattern: "The core thesis of the "midlayer mistake" is that midlayers are bad and should not exist. That common functionality which it is so tempting to put in a midlayer should instead be provided as library routines which can [be] used, augmented, or ignored by each bottom level driver independently. Thus every subsystem that supports multiple implementations (or drivers) should provide a very thin top layer which calls directly into the bottom layer drivers, and a rich library of support code that eases the implementation of those drivers. This library is available to, but not forced upon, those drivers." -- Neil Brown (2009), https://lwn.net/Articles/336262/ The presence of midlayer traits in the PCI hotplug core might be ascribed to its age: When it was introduced in February 2002, the blessings of a library approach might not have been well known: https://git.kernel.org/tglx/history/c/a8a2069f432c For comparison, the driver core does offer split functions for creating a kobject (device_initialize()) and addition to sysfs (device_add()) as an alternative to carrying out everything at once (device_register()). This was introduced in October 2002: https://git.kernel.org/tglx/history/c/8b290eb19962 The odd ->release callback in the PCI hotplug core was added in 2003: https://git.kernel.org/tglx/history/c/69f8d663b595 Clearly, a library approach would not force every hotplug driver to implement a ->release callback, but rather allow the driver to remove the sysfs files, release its data structures and finally destroy the kobject. Alternatively, a driver may choose to remove everything with pci_hp_deregister(), then release its data structures. To this end, offer drivers pci_hp_initialize() and pci_hp_add() as a split-up version of pci_hp_register(). Likewise, offer pci_hp_del() and pci_hp_destroy() as a split-up version of pci_hp_deregister(). Eliminate the ->release callback and move its code into each driver's teardown routine. Declare pci_hp_deregister() void, in keeping with the usual kernel pattern that enablement can fail, but disablement cannot. It only returned an error if the caller passed in a NULL pointer or a slot which has never or is no longer registered or is sharing its name with another slot. Those would be bugs, so WARN about them. Few hotplug drivers actually checked the return value and those that did only printed a useless error message to dmesg. Remove that. For most drivers the conversion was straightforward since it doesn't matter whether the code in the ->release callback is executed before or after destruction of the kobject. But in the case of ibmphp, it was unclear to me whether setting slot_cur->ctrl and slot_cur->bus_on to NULL needs to happen before the kobject is destroyed, so I erred on the side of caution and ensured that the order stays the same. Another nontrivial case is pnv_php, I've found the list and kref logic difficult to understand, however my impression was that it is safe to delete the list element and drop the references until after the kobject is destroyed. Signed-off-by: Lukas Wunner Signed-off-by: Bjorn Helgaas Acked-by: Andy Shevchenko # drivers/platform/x86 Cc: Rafael J. Wysocki Cc: Len Brown Cc: Scott Murray Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Cc: Michael Ellerman Cc: Gavin Shan Cc: Sebastian Ott Cc: Gerald Schaefer Cc: Corentin Chary Cc: Darren Hart Cc: Andy Shevchenko