e57d70c59b
[ Upstream commit 2dcb3964544177c51853a210b6ad400de78ef17d ] With kaslr the kernel image is placed at a random place, so starting the bottom-up allocation with the kernel_end can result in an allocation failure and a warning like this one: hugetlb_cma: reserve 2048 MiB, up to 2048 MiB per node ------------[ cut here ]------------ memblock: bottom-up allocation failed, memory hotremove may be affected WARNING: CPU: 0 PID: 0 at mm/memblock.c:332 memblock_find_in_range_node+0x178/0x25a Modules linked in: CPU: 0 PID: 0 Comm: swapper Not tainted 5.10.0+ #1169 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014 RIP: 0010:memblock_find_in_range_node+0x178/0x25a Code: e9 6d ff ff ff 48 85 c0 0f 85 da 00 00 00 80 3d 9b 35 df 00 00 75 15 48 c7 c7 c0 75 59 88 c6 05 8b 35 df 00 01 e8 25 8a fa ff <0f> 0b 48 c7 44 24 20 ff ff ff ff 44 89 e6 44 89 ea 48 c7 c1 70 5c RSP: 0000:ffffffff88803d18 EFLAGS: 00010086 ORIG_RAX: 0000000000000000 RAX: 0000000000000000 RBX: 0000000240000000 RCX: 00000000ffffdfff RDX: 00000000ffffdfff RSI: 00000000ffffffea RDI: 0000000000000046 RBP: 0000000100000000 R08: ffffffff88922788 R09: 0000000000009ffb R10: 00000000ffffe000 R11: 3fffffffffffffff R12: 0000000000000000 R13: 0000000000000000 R14: 0000000080000000 R15: 00000001fb42c000 FS: 0000000000000000(0000) GS:ffffffff88f71000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffa080fb401000 CR3: 00000001fa80a000 CR4: 00000000000406b0 Call Trace: memblock_alloc_range_nid+0x8d/0x11e cma_declare_contiguous_nid+0x2c4/0x38c hugetlb_cma_reserve+0xdc/0x128 flush_tlb_one_kernel+0xc/0x20 native_set_fixmap+0x82/0xd0 flat_get_apic_id+0x5/0x10 register_lapic_address+0x8e/0x97 setup_arch+0x8a5/0xc3f start_kernel+0x66/0x547 load_ucode_bsp+0x4c/0xcd secondary_startup_64_no_verify+0xb0/0xbb random: get_random_bytes called from __warn+0xab/0x110 with crng_init=0 ---[ end trace f151227d0b39be70 ]--- At the same time, the kernel image is protected with memblock_reserve(), so we can just start searching at PAGE_SIZE. In this case the bottom-up allocation has the same chances to success as a top-down allocation, so there is no reason to fallback in the case of a failure. All together it simplifies the logic. Link: https://lkml.kernel.org/r/20201217201214.3414100-2-guro@fb.com Fixes: 8fabc623238e ("powerpc: Ensure that swiotlb buffer is allocated from low memory") Signed-off-by: Roman Gushchin <guro@fb.com> Reviewed-by: Mike Rapoport <rppt@linux.ibm.com> Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com> Cc: Michal Hocko <mhocko@kernel.org> Cc: Rik van Riel <riel@surriel.com> Cc: Wonhyuk Yang <vvghjk1234@gmail.com> Cc: Thiago Jung Bauermann <bauerman@linux.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org> |
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README
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.