kernel/linux.git/tools/testing/memblock/tests, branch v6.19.11

memblock: add MEMBLOCK_RSRV_KERN flag

2025-05-13T06:50:38+00:00

Patch series "kexec: introduce Kexec HandOver (KHO)", v8. Kexec today considers itself purely a boot loader: When we enter the new kernel, any state the previous kernel left behind is irrelevant and the new kernel reinitializes the system. However, there are use cases where this mode of operation is not what we actually want. In virtualization hosts for example, we want to use kexec to update the host kernel while virtual machine memory stays untouched. When we add device assignment to the mix, we also need to ensure that IOMMU and VFIO states are untouched. If we add PCIe peer to peer DMA, we need to do the same for the PCI subsystem. If we want to kexec while an SEV-SNP enabled virtual machine is running, we need to preserve the VM context pages and physical memory. See "pkernfs: Persisting guest memory and kernel/device state safely across kexec" Linux Plumbers Conference 2023 presentation for details: https://lpc.events/event/17/contributions/1485/ To start us on the journey to support all the use cases above, this patch implements basic infrastructure to allow hand over of kernel state across kexec (Kexec HandOver, aka KHO). As a really simple example target, we use memblock's reserve_mem. With this patchset applied, memory that was reserved using "reserve_mem" command line options remains intact after kexec and it is guaranteed to reside at the same physical address. == Alternatives == There are alternative approaches to (parts of) the problems above: * Memory Pools [1] - preallocated persistent memory region + allocator * PRMEM [2] - resizable persistent memory regions with fixed metadata pointer on the kernel command line + allocator * Pkernfs [3] - preallocated file system for in-kernel data with fixed address location on the kernel command line * PKRAM [4] - handover of user space pages using a fixed metadata page specified via command line All of the approaches above fundamentally have the same problem: They require the administrator to explicitly carve out a physical memory location because they have no mechanism outside of the kernel command line to pass data (including memory reservations) between kexec'ing kernels. KHO provides that base foundation. We will determine later whether we still need any of the approaches above for fast bulk memory handover of for example IOMMU page tables. But IMHO they would all be users of KHO, with KHO providing the foundational primitive to pass metadata and bulk memory reservations as well as provide easy versioning for data. == Overview == We introduce a metadata file that the kernels pass between each other. How they pass it is architecture specific. The file's format is a Flattened Device Tree (fdt) which has a generator and parser already included in Linux. KHO is enabled in the kernel command line by `kho=on`. When the root user enables KHO through /sys/kernel/debug/kho/out/finalize, the kernel invokes callbacks to every KHO users to register preserved memory regions, which contain drivers' states. When the actual kexec happens, the fdt is part of the image set that we boot into. In addition, we keep "scratch regions" available for kexec: physically contiguous memory regions that are guaranteed to not have any memory that KHO would preserve. The new kernel bootstraps itself using the scratch regions and sets all handed over memory as in use. When drivers initialize that support KHO, they introspect the fdt, restore preserved memory regions, and retrieve their states stored in the preserved memory. == Limitations == Currently KHO is only implemented for file based kexec. The kernel interfaces in the patch set are already in place to support user space kexec as well, but it is still not implemented it yet inside kexec tools. == How to Use == To use the code, please boot the kernel with the "kho=on" command line parameter. KHO will automatically create scratch regions. If you want to set the scratch size explicitly you can use "kho_scratch=" command line parameter. For instance, "kho_scratch=16M,512M,256M" will reserve a 16 MiB low memory scratch area, a 512 MiB global scratch region, and 256 MiB per NUMA node scratch regions on boot. Make sure to have a reserved memory range requested with reserv_mem command line option, for example, "reserve_mem=64m:4k:n1". Then before you invoke file based "kexec -l", finalize KHO FDT: # echo 1 > /sys/kernel/debug/kho/out/finalize You can preview the generated FDT using `dtc`, # dtc /sys/kernel/debug/kho/out/fdt # dtc /sys/kernel/debug/kho/out/sub_fdts/memblock `dtc` is available on ubuntu by `sudo apt-get install device-tree-compiler`. Now kexec into the new kernel, # kexec -l Image --initrd=initrd -s # kexec -e (The order of KHO finalization and "kexec -l" does not matter.) The new kernel will boot up and contain the previous kernel's reserve_mem contents at the same physical address as the first kernel. You can also review the FDT passed from the old kernel, # dtc /sys/kernel/debug/kho/in/fdt # dtc /sys/kernel/debug/kho/in/sub_fdts/memblock This patch (of 17): To denote areas that were reserved for kernel use either directly with memblock_reserve_kern() or via memblock allocations. Link: https://lore.kernel.org/lkml/20250424083258.2228122-1-changyuanl@google.com/ Link: https://lore.kernel.org/lkml/aAeaJ2iqkrv_ffhT@kernel.org/ Link: https://lore.kernel.org/lkml/35c58191-f774-40cf-8d66-d1e2aaf11a62@intel.com/ Link: https://lore.kernel.org/lkml/20250424093302.3894961-1-arnd@kernel.org/ Link: https://lkml.kernel.org/r/20250509074635.3187114-1-changyuanl@google.com Link: https://lkml.kernel.org/r/20250509074635.3187114-2-changyuanl@google.com Signed-off-by: Mike Rapoport (Microsoft) Co-developed-by: Changyuan Lyu Signed-off-by: Changyuan Lyu Cc: Alexander Graf Cc: Andy Lutomirski Cc: Anthony Yznaga Cc: Arnd Bergmann Cc: Ashish Kalra Cc: Ben Herrenschmidt Cc: Borislav Betkov Cc: Catalin Marinas Cc: David Woodhouse Cc: Eric Biederman Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: James Gowans Cc: Jonathan Corbet Cc: Krzysztof Kozlowski Cc: Marc Rutland Cc: Paolo Bonzini Cc: Pasha Tatashin Cc: Peter Zijlstra Cc: Pratyush Yadav Cc: Rob Herring Cc: Saravana Kannan Cc: Stanislav Kinsburskii Cc: Steven Rostedt Cc: Thomas Gleinxer Cc: Thomas Lendacky Cc: Will Deacon Cc: Dave Hansen Cc: Jason Gunthorpe Signed-off-by: Andrew Morton

memblock tests: add test for memblock_set_node

2025-04-07T06:28:01+00:00

Add a test to check memblock_set_node() behavior. And create a corner case in which the memblock.reserved array is doubled during memblock_set_node(). And finally make sure all regions in memblock.reserved are with valid node id. Signed-off-by: Wei Yang CC: Mike Rapoport CC: Yajun Deng Link: https://lore.kernel.org/r/20250318071948.23854-4-richard.weiyang@gmail.com Signed-off-by: Mike Rapoport (Microsoft)

memblock tests: add memblock_overlaps_region_checks

2024-06-05T07:22:22+00:00

Add a test case for memblock_overlaps_region(). Signed-off-by: Wei Yang Link: https://lore.kernel.org/r/20240507075833.6346-5-richard.weiyang@gmail.com Signed-off-by: Mike Rapoport (IBM)

memblock tests: add memblock_reserve_many_may_conflict_check()

2024-06-05T07:22:22+00:00

This may trigger the case fixed by commit 48c3b583bbdd ("mm/memblock: fix overlapping allocation when doubling reserved array"). This is done by adding the 129th reserve region into memblock.memory. If memblock_double_array() use this reserve region as new array, it fails. Signed-off-by: Wei Yang Link: https://lore.kernel.org/r/20240507075833.6346-3-richard.weiyang@gmail.com Signed-off-by: Mike Rapoport (IBM)

memblock tests: add memblock_reserve_all_locations_check()

2024-06-05T07:22:21+00:00

Instead of adding 129th memory block at the last position, let's try all possible position. Signed-off-by: Wei Yang Link: https://lore.kernel.org/r/20240507075833.6346-2-richard.weiyang@gmail.com Signed-off-by: Mike Rapoport (IBM)

mm/memblock: remove empty dummy entry

2024-06-05T07:21:47+00:00

The dummy entry is introduced in the initial implementation of lmb in commit 7c8c6b9776fb ("powerpc: Merge lmb.c and make MM initialization use it."). As the comment says the empty dummy entry is to simplify the code. /* Create a dummy zero size LMB which will get coalesced away later. * This simplifies the lmb_add() code below... */ While current code is reimplemented by Tejun in commit 784656f9c680 ("memblock: Reimplement memblock_add_region()"). This empty dummy entry seems not benefit the code any more. Let's remove it. Signed-off-by: Wei Yang CC: Paul Mackerras CC: Tejun Heo CC: Mike Rapoport Link: https://lore.kernel.org/r/20240405015821.13411-1-richard.weiyang@gmail.com Signed-off-by: Mike Rapoport (IBM)

memblock tests: fix warning ‘struct seq_file’ declared inside parameter list

2023-09-14T07:51:28+00:00

Building memblock tests produces the following warning: cc -I. -I../../include -Wall -O2 -fsanitize=address -fsanitize=undefined -D CONFIG_PHYS_ADDR_T_64BIT -c -o main.o main.c In file included from tests/common.h:9, from tests/basic_api.h:5, from main.c:2: ./linux/memblock.h:601:50: warning: ‘struct seq_file’ declared inside parameter list will not be visible outside of this definition or declaration 601 | static inline void memtest_report_meminfo(struct seq_file *m) { } | ^~~~~~~~ Add declaration of 'struct seq_file' to tools/include/linux/seq_file.h to fix it. Signed-off-by: Mike Rapoport (IBM)

Add tests for memblock_alloc_node()

2023-05-24T08:56:30+00:00

This test is aimed at verifying the memblock_alloc_node() to work as expected, so setting the correct NUMA node for the new allocated region. The memblock_alloc_node() is called directly without using any stub. The core check is between the requested NUMA node and the `nid` field inside the memblock_region structure. These two are supposed to be equal for the test to succeed. Signed-off-by: Claudio Migliorelli Link: https://lore.kernel.org/r/ea5e938e-6b74-b188-af59-4b94b18bc0@mail.polimi.it Signed-off-by: Mike Rapoport (IBM)

memblock tests: add generic NUMA tests for memblock_alloc_exact_nid_raw

2022-11-08T07:50:24+00:00

Add tests for memblock_alloc_exact_nid_raw() where the simulated physical memory is set up with multiple NUMA nodes. Additionally, all but one of these tests set nid != NUMA_NO_NODE. All tests are run for both top-down and bottom-up allocation directions. The tested scenarios are: Range unrestricted: - region cannot be allocated: + there are no previously reserved regions, but requested node is too small + the requested node is fully reserved + the requested node is partially reserved and does not have enough space + none of the nodes have enough memory to allocate the region Range restricted: - region can be allocated in the specific node requested without dropping min_addr: + the range fully overlaps with the node, and there are adjacent reserved regions - region cannot be allocated: + range partially overlaps with two different nodes, where the second node is the requested node + range overlaps with multiple nodes along node boundaries, and the requested node starts after max_addr + nid is set to NUMA_NO_NODE and the total range can fit the region, but the range is split between two nodes and everything else is reserved Acked-by: David Hildenbrand Signed-off-by: Rebecca Mckeever Signed-off-by: Mike Rapoport Link: https://lore.kernel.org/r/51b14da46e6591428df3aefc5acc7dca9341a541.1667802195.git.remckee0@gmail.com

memblock tests: add bottom-up NUMA tests for memblock_alloc_exact_nid_raw

2022-11-08T07:50:24+00:00

Add tests for memblock_alloc_exact_nid_raw() where the simulated physical memory is set up with multiple NUMA nodes. Additionally, all of these tests set nid != NUMA_NO_NODE. These tests are run with a bottom-up allocation direction. The tested scenarios are: Range unrestricted: - region can be allocated in the specific node requested: + there are no previously reserved regions + the requested node is partially reserved but has enough space Range restricted: - region can be allocated in the specific node requested after dropping min_addr: + range partially overlaps with two different nodes, where the first node is the requested node + range partially overlaps with two different nodes, where the requested node ends before min_addr + range overlaps with multiple nodes along node boundaries, and the requested node ends before min_addr Acked-by: David Hildenbrand Signed-off-by: Rebecca Mckeever Signed-off-by: Mike Rapoport Link: https://lore.kernel.org/r/935f0eed5e06fd44dc67d9f49b277923d7896bd3.1667802195.git.remckee0@gmail.com