kernel/linux.git/tools/testing/memblock, 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: Fix mutex related build error

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

Fix mutex and free_reserved_area() related build errors which have been introduced by commit 74e2498ccf7b ("mm/memblock: Add reserved memory release function"). Fixes: 74e2498ccf7b ("mm/memblock: Add reserved memory release function") Reported-by: Wei Yang Closes: https://lore.kernel.org/all/20250405023018.g2ae52nrz2757b3n@master/ Signed-off-by: Masami Hiramatsu (Google) Link: https://lore.kernel.org/r/174399023133.47537.7375975856054461445.stgit@devnote2 Signed-off-by: Mike Rapoport (Microsoft)

Merge tag 'memblock-v6.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock

2024-09-25T18:35:19+00:00

Pull memblock updates from Mike Rapoport: - new memblock_estimated_nr_free_pages() helper to replace totalram_pages() which is less accurate when CONFIG_DEFERRED_STRUCT_PAGE_INIT is set - fixes for memblock tests * tag 'memblock-v6.12-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/rppt/memblock: s390/mm: get estimated free pages by memblock api kernel/fork.c: get estimated free pages by memblock api mm/memblock: introduce a new helper memblock_estimated_nr_free_pages() memblock test: fix implicit declaration of function 'strscpy' memblock test: fix implicit declaration of function 'isspace' memblock test: fix implicit declaration of function 'memparse' memblock test: add the definition of __setup() memblock test: fix implicit declaration of function 'virt_to_phys' tools/testing: abstract two init.h into common include directory memblock tests: include export.h in linkage.h as kernel dose memblock tests: include memory_hotplug.h in mmzone.h as kernel dose

mm: rework accept memory helpers

2024-09-02T03:26:07+00:00

Make accept_memory() and range_contains_unaccepted_memory() take 'start' and 'size' arguments instead of 'start' and 'end'. Remove accept_page(), replacing it with direct calls to accept_memory(). The accept_page() name is going to be used for a different function. Link: https://lkml.kernel.org/r/20240809114854.3745464-6-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov Suggested-by: David Hildenbrand Cc: Borislav Petkov Cc: Johannes Weiner Cc: Matthew Wilcox Cc: Mel Gorman Cc: Mike Rapoport (Microsoft) Cc: Tom Lendacky Cc: Vlastimil Babka Signed-off-by: Andrew Morton

memblock test: fix implicit declaration of function 'isspace'

2024-08-06T05:21:25+00:00

Commit 1e4c64b71c9b ("mm/memblock: Add "reserve_mem" to reserved named memory at boot up") introduce usage of isspace(). Let's include in kernel.h to fix this. Signed-off-by: Wei Yang Link: https://lore.kernel.org/r/20240806010319.29194-4-richard.weiyang@gmail.com Signed-off-by: Mike Rapoport (Microsoft)

memblock test: fix implicit declaration of function 'memparse'

2024-08-06T05:21:25+00:00

Commit 1e4c64b71c9b ("mm/memblock: Add "reserve_mem" to reserved named memory at boot up") introduce the usage of memparse(), which is not defined in memblock test. Add the definition and link it to fix the build. Signed-off-by: Wei Yang Link: https://lore.kernel.org/r/20240806010319.29194-3-richard.weiyang@gmail.com Signed-off-by: Mike Rapoport (Microsoft)

tools/testing: abstract two init.h into common include directory

2024-08-06T05:17:50+00:00

Currently we have two test suits define its own init.h. This is a little redundant. Let's create a init.h in common include directory and merge these two into it. Signed-off-by: Wei Yang CC: Mike Rapoport CC: Liam R. Howlett Link: https://lore.kernel.org/r/20240712035138.24674-3-richard.weiyang@gmail.com Signed-off-by: Mike Rapoport (Microsoft)

memblock tests: include export.h in linkage.h as kernel dose

2024-08-06T05:17:49+00:00

In kernel code, linkage.h includes export.h. Let's sync with kernel. This is a preparation for move init.h in common include directory. Signed-off-by: Wei Yang CC: Mike Rapoport Link: https://lore.kernel.org/r/20240712035138.24674-2-richard.weiyang@gmail.com Signed-off-by: Mike Rapoport (Microsoft)

memblock tests: include memory_hotplug.h in mmzone.h as kernel dose

2024-08-06T05:17:49+00:00

In kernel code, memory_hotplug.h is included in mmzone.h instead of in init.h. Let's sync with kernel. This is a preparation for move init.h in common include directory. Signed-off-by: Wei Yang CC: Mike Rapoport Link: https://lore.kernel.org/r/20240712035138.24674-1-richard.weiyang@gmail.com Signed-off-by: Mike Rapoport (Microsoft)