diff options
Diffstat (limited to 'Documentation/admin-guide')
| -rw-r--r-- | Documentation/admin-guide/devices.txt | 2 | ||||
| -rw-r--r-- | Documentation/admin-guide/gpio/gpio-mockup.rst | 11 | ||||
| -rw-r--r-- | Documentation/admin-guide/kernel-parameters.txt | 65 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/memory-hotplug.rst | 9 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/transhuge.rst | 2 | ||||
| -rw-r--r-- | Documentation/admin-guide/mm/userfaultfd.rst | 107 | ||||
| -rw-r--r-- | Documentation/admin-guide/reporting-issues.rst | 49 | ||||
| -rw-r--r-- | Documentation/admin-guide/sysctl/net.rst | 13 |
8 files changed, 178 insertions, 80 deletions
diff --git a/Documentation/admin-guide/devices.txt b/Documentation/admin-guide/devices.txt index ef41f77cb979..9c2be821c225 100644 --- a/Documentation/admin-guide/devices.txt +++ b/Documentation/admin-guide/devices.txt @@ -4,7 +4,7 @@ 1 char Memory devices 1 = /dev/mem Physical memory access - 2 = /dev/kmem Kernel virtual memory access + 2 = /dev/kmem OBSOLETE - replaced by /proc/kcore 3 = /dev/null Null device 4 = /dev/port I/O port access 5 = /dev/zero Null byte source diff --git a/Documentation/admin-guide/gpio/gpio-mockup.rst b/Documentation/admin-guide/gpio/gpio-mockup.rst index 9fa1618b3adc..493071da1738 100644 --- a/Documentation/admin-guide/gpio/gpio-mockup.rst +++ b/Documentation/admin-guide/gpio/gpio-mockup.rst @@ -17,17 +17,18 @@ module. gpio_mockup_ranges This parameter takes an argument in the form of an array of integer - pairs. Each pair defines the base GPIO number (if any) and the number - of lines exposed by the chip. If the base GPIO is -1, the gpiolib - will assign it automatically. + pairs. Each pair defines the base GPIO number (non-negative integer) + and the first number after the last of this chip. If the base GPIO + is -1, the gpiolib will assign it automatically. while the following + parameter is the number of lines exposed by the chip. - Example: gpio_mockup_ranges=-1,8,-1,16,405,4 + Example: gpio_mockup_ranges=-1,8,-1,16,405,409 The line above creates three chips. The first one will expose 8 lines, the second 16 and the third 4. The base GPIO for the third chip is set to 405 while for two first chips it will be assigned automatically. - gpio_named_lines + gpio_mockup_named_lines This parameter doesn't take any arguments. It lets the driver know that GPIO lines exposed by it should be named. diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 5c949c12ed07..cb89dbdedc46 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -1469,6 +1469,12 @@ Don't use this when you are not running on the android emulator + gpio-mockup.gpio_mockup_ranges + [HW] Sets the ranges of gpiochip of for this device. + Format: <start1>,<end1>,<start2>,<end2>... + gpio-mockup.gpio_mockup_named_lines + [HW] Let the driver know GPIO lines should be named. + gpt [EFI] Forces disk with valid GPT signature but invalid Protective MBR to be treated as GPT. If the primary GPT is corrupted, it enables the backup/alternate @@ -1492,10 +1498,6 @@ Format: <unsigned int> such that (rxsize & ~0x1fffc0) == 0. Default: 1024 - gpio-mockup.gpio_mockup_ranges - [HW] Sets the ranges of gpiochip of for this device. - Format: <start1>,<end1>,<start2>,<end2>... - hardlockup_all_cpu_backtrace= [KNL] Should the hard-lockup detector generate backtraces on all cpus. @@ -1833,6 +1835,18 @@ initcall functions. Useful for debugging built-in modules and initcalls. + initramfs_async= [KNL] + Format: <bool> + Default: 1 + This parameter controls whether the initramfs + image is unpacked asynchronously, concurrently + with devices being probed and + initialized. This should normally just work, + but as a debugging aid, one can get the + historical behaviour of the initramfs + unpacking being completed before device_ and + late_ initcalls. + initrd= [BOOT] Specify the location of the initial ramdisk initrdmem= [KNL] Specify a physical address and size from which to @@ -1877,13 +1891,6 @@ bypassed by not enabling DMAR with this option. In this case, gfx device will use physical address for DMA. - forcedac [X86-64] - With this option iommu will not optimize to look - for io virtual address below 32-bit forcing dual - address cycle on pci bus for cards supporting greater - than 32-bit addressing. The default is to look - for translation below 32-bit and if not available - then look in the higher range. strict [Default Off] With this option on every unmap_single operation will result in a hardware IOTLB flush operation as opposed @@ -1972,6 +1979,14 @@ nobypass [PPC/POWERNV] Disable IOMMU bypass, using IOMMU for PCI devices. + iommu.forcedac= [ARM64, X86] Control IOVA allocation for PCI devices. + Format: { "0" | "1" } + 0 - Try to allocate a 32-bit DMA address first, before + falling back to the full range if needed. + 1 - Allocate directly from the full usable range, + forcing Dual Address Cycle for PCI cards supporting + greater than 32-bit addressing. + iommu.strict= [ARM64] Configure TLB invalidation behaviour Format: { "0" | "1" } 0 - Lazy mode. @@ -2801,7 +2816,24 @@ seconds. Use this parameter to check at some other rate. 0 disables periodic checking. - memtest= [KNL,X86,ARM,PPC] Enable memtest + memory_hotplug.memmap_on_memory + [KNL,X86,ARM] Boolean flag to enable this feature. + Format: {on | off (default)} + When enabled, runtime hotplugged memory will + allocate its internal metadata (struct pages) + from the hotadded memory which will allow to + hotadd a lot of memory without requiring + additional memory to do so. + This feature is disabled by default because it + has some implication on large (e.g. GB) + allocations in some configurations (e.g. small + memory blocks). + The state of the flag can be read in + /sys/module/memory_hotplug/parameters/memmap_on_memory. + Note that even when enabled, there are a few cases where + the feature is not effective. + + memtest= [KNL,X86,ARM,PPC,RISCV] Enable memtest Format: <integer> default : 0 <disable> Specifies the number of memtest passes to be @@ -3250,6 +3282,8 @@ nohugeiomap [KNL,X86,PPC,ARM64] Disable kernel huge I/O mappings. + nohugevmalloc [PPC] Disable kernel huge vmalloc mappings. + nosmt [KNL,S390] Disable symmetric multithreading (SMT). Equivalent to smt=1. @@ -4996,6 +5030,10 @@ slram= [HW,MTD] + slab_merge [MM] + Enable merging of slabs with similar size when the + kernel is built without CONFIG_SLAB_MERGE_DEFAULT. + slab_nomerge [MM] Disable merging of slabs with similar size. May be necessary if there is some reason to distinguish @@ -5043,6 +5081,9 @@ lower than slub_max_order. For more information see Documentation/vm/slub.rst. + slub_merge [MM, SLUB] + Same with slab_merge. + slub_nomerge [MM, SLUB] Same with slab_nomerge. This is supported for legacy. See slab_nomerge for more information. diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst index 5307f90738aa..05d51d2d8beb 100644 --- a/Documentation/admin-guide/mm/memory-hotplug.rst +++ b/Documentation/admin-guide/mm/memory-hotplug.rst @@ -357,6 +357,15 @@ creates ZONE_MOVABLE as following. Unfortunately, there is no information to show which memory block belongs to ZONE_MOVABLE. This is TBD. +.. note:: + Techniques that rely on long-term pinnings of memory (especially, RDMA and + vfio) are fundamentally problematic with ZONE_MOVABLE and, therefore, memory + hot remove. Pinned pages cannot reside on ZONE_MOVABLE, to guarantee that + memory can still get hot removed - be aware that pinning can fail even if + there is plenty of free memory in ZONE_MOVABLE. In addition, using + ZONE_MOVABLE might make page pinning more expensive, because pages have to be + migrated off that zone first. + .. _memory_hotplug_how_to_offline_memory: How to offline memory diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/admin-guide/mm/transhuge.rst index 3b8a336511a4..c9c37f16eef8 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -402,7 +402,7 @@ compact_fail but failed. It is possible to establish how long the stalls were using the function -tracer to record how long was spent in __alloc_pages_nodemask and +tracer to record how long was spent in __alloc_pages() and using the mm_page_alloc tracepoint to identify which allocations were for huge pages. diff --git a/Documentation/admin-guide/mm/userfaultfd.rst b/Documentation/admin-guide/mm/userfaultfd.rst index 65eefa66c0ba..3aa38e8b8361 100644 --- a/Documentation/admin-guide/mm/userfaultfd.rst +++ b/Documentation/admin-guide/mm/userfaultfd.rst @@ -63,36 +63,36 @@ the generic ioctl available. The ``uffdio_api.features`` bitmask returned by the ``UFFDIO_API`` ioctl defines what memory types are supported by the ``userfaultfd`` and what -events, except page fault notifications, may be generated. - -If the kernel supports registering ``userfaultfd`` ranges on hugetlbfs -virtual memory areas, ``UFFD_FEATURE_MISSING_HUGETLBFS`` will be set in -``uffdio_api.features``. Similarly, ``UFFD_FEATURE_MISSING_SHMEM`` will be -set if the kernel supports registering ``userfaultfd`` ranges on shared -memory (covering all shmem APIs, i.e. tmpfs, ``IPCSHM``, ``/dev/zero``, -``MAP_SHARED``, ``memfd_create``, etc). - -The userland application that wants to use ``userfaultfd`` with hugetlbfs -or shared memory need to set the corresponding flag in -``uffdio_api.features`` to enable those features. - -If the userland desires to receive notifications for events other than -page faults, it has to verify that ``uffdio_api.features`` has appropriate -``UFFD_FEATURE_EVENT_*`` bits set. These events are described in more -detail below in `Non-cooperative userfaultfd`_ section. - -Once the ``userfaultfd`` has been enabled the ``UFFDIO_REGISTER`` ioctl should -be invoked (if present in the returned ``uffdio_api.ioctls`` bitmask) to -register a memory range in the ``userfaultfd`` by setting the +events, except page fault notifications, may be generated: + +- The ``UFFD_FEATURE_EVENT_*`` flags indicate that various other events + other than page faults are supported. These events are described in more + detail below in the `Non-cooperative userfaultfd`_ section. + +- ``UFFD_FEATURE_MISSING_HUGETLBFS`` and ``UFFD_FEATURE_MISSING_SHMEM`` + indicate that the kernel supports ``UFFDIO_REGISTER_MODE_MISSING`` + registrations for hugetlbfs and shared memory (covering all shmem APIs, + i.e. tmpfs, ``IPCSHM``, ``/dev/zero``, ``MAP_SHARED``, ``memfd_create``, + etc) virtual memory areas, respectively. + +- ``UFFD_FEATURE_MINOR_HUGETLBFS`` indicates that the kernel supports + ``UFFDIO_REGISTER_MODE_MINOR`` registration for hugetlbfs virtual memory + areas. + +The userland application should set the feature flags it intends to use +when invoking the ``UFFDIO_API`` ioctl, to request that those features be +enabled if supported. + +Once the ``userfaultfd`` API has been enabled the ``UFFDIO_REGISTER`` +ioctl should be invoked (if present in the returned ``uffdio_api.ioctls`` +bitmask) to register a memory range in the ``userfaultfd`` by setting the uffdio_register structure accordingly. The ``uffdio_register.mode`` bitmask will specify to the kernel which kind of faults to track for -the range (``UFFDIO_REGISTER_MODE_MISSING`` would track missing -pages). The ``UFFDIO_REGISTER`` ioctl will return the +the range. The ``UFFDIO_REGISTER`` ioctl will return the ``uffdio_register.ioctls`` bitmask of ioctls that are suitable to resolve userfaults on the range registered. Not all ioctls will necessarily be -supported for all memory types depending on the underlying virtual -memory backend (anonymous memory vs tmpfs vs real filebacked -mappings). +supported for all memory types (e.g. anonymous memory vs. shmem vs. +hugetlbfs), or all types of intercepted faults. Userland can use the ``uffdio_register.ioctls`` to manage the virtual address space in the background (to add or potentially also remove @@ -100,21 +100,46 @@ memory from the ``userfaultfd`` registered range). This means a userfault could be triggering just before userland maps in the background the user-faulted page. -The primary ioctl to resolve userfaults is ``UFFDIO_COPY``. That -atomically copies a page into the userfault registered range and wakes -up the blocked userfaults -(unless ``uffdio_copy.mode & UFFDIO_COPY_MODE_DONTWAKE`` is set). -Other ioctl works similarly to ``UFFDIO_COPY``. They're atomic as in -guaranteeing that nothing can see an half copied page since it'll -keep userfaulting until the copy has finished. +Resolving Userfaults +-------------------- + +There are three basic ways to resolve userfaults: + +- ``UFFDIO_COPY`` atomically copies some existing page contents from + userspace. + +- ``UFFDIO_ZEROPAGE`` atomically zeros the new page. + +- ``UFFDIO_CONTINUE`` maps an existing, previously-populated page. + +These operations are atomic in the sense that they guarantee nothing can +see a half-populated page, since readers will keep userfaulting until the +operation has finished. + +By default, these wake up userfaults blocked on the range in question. +They support a ``UFFDIO_*_MODE_DONTWAKE`` ``mode`` flag, which indicates +that waking will be done separately at some later time. + +Which ioctl to choose depends on the kind of page fault, and what we'd +like to do to resolve it: + +- For ``UFFDIO_REGISTER_MODE_MISSING`` faults, the fault needs to be + resolved by either providing a new page (``UFFDIO_COPY``), or mapping + the zero page (``UFFDIO_ZEROPAGE``). By default, the kernel would map + the zero page for a missing fault. With userfaultfd, userspace can + decide what content to provide before the faulting thread continues. + +- For ``UFFDIO_REGISTER_MODE_MINOR`` faults, there is an existing page (in + the page cache). Userspace has the option of modifying the page's + contents before resolving the fault. Once the contents are correct + (modified or not), userspace asks the kernel to map the page and let the + faulting thread continue with ``UFFDIO_CONTINUE``. Notes: -- If you requested ``UFFDIO_REGISTER_MODE_MISSING`` when registering then - you must provide some kind of page in your thread after reading from - the uffd. You must provide either ``UFFDIO_COPY`` or ``UFFDIO_ZEROPAGE``. - The normal behavior of the OS automatically providing a zero page on - an anonymous mmaping is not in place. +- You can tell which kind of fault occurred by examining + ``pagefault.flags`` within the ``uffd_msg``, checking for the + ``UFFD_PAGEFAULT_FLAG_*`` flags. - None of the page-delivering ioctls default to the range that you registered with. You must fill in all fields for the appropriate @@ -122,9 +147,9 @@ Notes: - You get the address of the access that triggered the missing page event out of a struct uffd_msg that you read in the thread from the - uffd. You can supply as many pages as you want with ``UFFDIO_COPY`` or - ``UFFDIO_ZEROPAGE``. Keep in mind that unless you used DONTWAKE then - the first of any of those IOCTLs wakes up the faulting thread. + uffd. You can supply as many pages as you want with these IOCTLs. + Keep in mind that unless you used DONTWAKE then the first of any of + those IOCTLs wakes up the faulting thread. - Be sure to test for all errors including (``pollfd[0].revents & POLLERR``). This can happen, e.g. when ranges diff --git a/Documentation/admin-guide/reporting-issues.rst b/Documentation/admin-guide/reporting-issues.rst index 48b4d0ef2b09..18d8e25ba9df 100644 --- a/Documentation/admin-guide/reporting-issues.rst +++ b/Documentation/admin-guide/reporting-issues.rst @@ -24,7 +24,8 @@ longterm series? One still supported? Then search the `LKML you don't find any, install `the latest release from that series <https://kernel.org/>`_. If it still shows the issue, report it to the stable mailing list (stable@vger.kernel.org) and CC the regressions list -(regressions@lists.linux.dev). +(regressions@lists.linux.dev); ideally also CC the maintainer and the mailing +list for the subsystem in question. In all other cases try your best guess which kernel part might be causing the issue. Check the :ref:`MAINTAINERS <maintainers>` file for how its developers @@ -48,8 +49,9 @@ before the issue occurs. If you are facing multiple issues with the Linux kernel at once, report each separately. While writing your report, include all information relevant to the issue, like the kernel and the distro used. In case of a regression, CC the -regressions mailing list (regressions@lists.linux.dev) to your report; also try -to include the commit-id of the change causing it, which a bisection can find. +regressions mailing list (regressions@lists.linux.dev) to your report. Also try +to pin-point the culprit with a bisection; if you succeed, include its +commit-id and CC everyone in the sign-off-by chain. Once the report is out, answer any questions that come up and help where you can. That includes keeping the ball rolling by occasionally retesting with newer @@ -198,10 +200,11 @@ report them: * Send a short problem report to the Linux stable mailing list (stable@vger.kernel.org) and CC the Linux regressions mailing list - (regressions@lists.linux.dev). Roughly describe the issue and ideally - explain how to reproduce it. Mention the first version that shows the - problem and the last version that's working fine. Then wait for further - instructions. + (regressions@lists.linux.dev); if you suspect the cause in a particular + subsystem, CC its maintainer and its mailing list. Roughly describe the + issue and ideally explain how to reproduce it. Mention the first version + that shows the problem and the last version that's working fine. Then + wait for further instructions. The reference section below explains each of these steps in more detail. @@ -768,7 +771,9 @@ regular internet search engine and add something like the results to the archives at that URL. It's also wise to check the internet, LKML and maybe bugzilla.kernel.org again -at this point. +at this point. If your report needs to be filed in a bug tracker, you may want +to check the mailing list archives for the subsystem as well, as someone might +have reported it only there. For details how to search and what to do if you find matching reports see "Search for existing reports, first run" above. @@ -1249,9 +1254,10 @@ and the oldest where the issue occurs (say 5.8-rc1). When sending the report by mail, CC the Linux regressions mailing list (regressions@lists.linux.dev). In case the report needs to be filed to some web -tracker, proceed to do so; once filed, forward the report by mail to the -regressions list. Make sure to inline the forwarded report, hence do not attach -it. Also add a short note at the top where you mention the URL to the ticket. +tracker, proceed to do so. Once filed, forward the report by mail to the +regressions list; CC the maintainer and the mailing list for the subsystem in +question. Make sure to inline the forwarded report, hence do not attach it. +Also add a short note at the top where you mention the URL to the ticket. When mailing or forwarding the report, in case of a successful bisection add the author of the culprit to the recipients; also CC everyone in the signed-off-by @@ -1536,17 +1542,20 @@ Report the regression *Send a short problem report to the Linux stable mailing list (stable@vger.kernel.org) and CC the Linux regressions mailing list - (regressions@lists.linux.dev). Roughly describe the issue and ideally - explain how to reproduce it. Mention the first version that shows the - problem and the last version that's working fine. Then wait for further - instructions.* + (regressions@lists.linux.dev); if you suspect the cause in a particular + subsystem, CC its maintainer and its mailing list. Roughly describe the + issue and ideally explain how to reproduce it. Mention the first version + that shows the problem and the last version that's working fine. Then + wait for further instructions.* When reporting a regression that happens within a stable or longterm kernel line (say when updating from 5.10.4 to 5.10.5) a brief report is enough for -the start to get the issue reported quickly. Hence a rough description is all -it takes. +the start to get the issue reported quickly. Hence a rough description to the +stable and regressions mailing list is all it takes; but in case you suspect +the cause in a particular subsystem, CC its maintainers and its mailing list +as well, because that will speed things up. -But note, it helps developers a great deal if you can specify the exact version +And note, it helps developers a great deal if you can specify the exact version that introduced the problem. Hence if possible within a reasonable time frame, try to find that version using vanilla kernels. Lets assume something broke when your distributor released a update from Linux kernel 5.10.5 to 5.10.8. Then as @@ -1563,7 +1572,9 @@ pinpoint the exact change that causes the issue (which then can easily get reverted to fix the issue quickly). Hence consider to do a proper bisection right away if time permits. See the section 'Special care for regressions' and the document 'Documentation/admin-guide/bug-bisect.rst' for details how to -perform one. +perform one. In case of a successful bisection add the author of the culprit to +the recipients; also CC everyone in the signed-off-by chain, which you find at +the end of its commit message. Reference for "Reporting issues only occurring in older kernel version lines" diff --git a/Documentation/admin-guide/sysctl/net.rst b/Documentation/admin-guide/sysctl/net.rst index f2ab8a5b6a4b..4150f74c521a 100644 --- a/Documentation/admin-guide/sysctl/net.rst +++ b/Documentation/admin-guide/sysctl/net.rst @@ -64,6 +64,7 @@ two flavors of JITs, the newer eBPF JIT currently supported on: - arm64 - arm32 - ppc64 + - ppc32 - sparc64 - mips64 - s390x @@ -73,7 +74,6 @@ two flavors of JITs, the newer eBPF JIT currently supported on: And the older cBPF JIT supported on the following archs: - mips - - ppc - sparc eBPF JITs are a superset of cBPF JITs, meaning the kernel will @@ -311,6 +311,17 @@ permit to distribute the load on several cpus. If set to 1 (default), timestamps are sampled as soon as possible, before queueing. +netdev_unregister_timeout_secs +------------------------------ + +Unregister network device timeout in seconds. +This option controls the timeout (in seconds) used to issue a warning while +waiting for a network device refcount to drop to 0 during device +unregistration. A lower value may be useful during bisection to detect +a leaked reference faster. A larger value may be useful to prevent false +warnings on slow/loaded systems. +Default value is 10, minimum 1, maximum 3600. + optmem_max ---------- |