On Thu, 2025-02-06 at 11:16 +0100, Oleksandr Natalenko wrote: > Hello. > > On čtvrtek 6. února 2025 5:43:19, středoevropský standardní čas Rik > van Riel wrote: > > > > v9: > > - print warning when start or end address was rounded (Peter) > > OK, I've just hit one: > > TLB flush not stride 200000 aligned. Start 7fffc0000000, end > 7fffffe01000 Beautiful, the caller wants to zap 2MB pages, but the end address is 4kB aligned. > WARNING: CPU: 31 PID: 411 at arch/x86/mm/tlb.c:1342 > flush_tlb_mm_range+0x57b/0x600 > Modules linked in: > CPU: 31 UID: 0 PID: 411 Comm: modprobe Not tainted 6.13.0-pf3 #1 > 1366679ca06f46d05d1e9d9c537b0c6b4c922b82 > Hardware name: ASUS System Product Name/Pro WS X570-ACE, BIOS 4902 > 08/29/2024 > RIP: 0010:flush_tlb_mm_range+0x57b/0x600 > Code: 5f e9 39 b3 3f 00 e8 24 57 f5 ff e9 e9 fc ff ff 48 8b 0c 24 4c > 89 e2 48 c7 c7 78 59 27 b0 c6 05 3d 1a 31 02 01 e8 85 e4 01 00 <0f> > 0b e9 35 fb ff ff fa 0f 1f 44 00 00 48 89 df e8 a0 f4 ff ff fb > RSP: 0018:ffffc137c11e7a38 EFLAGS: 00010286 > RAX: 0000000000000000 RBX: ffff9e6eaf1b5d80 RCX: 00000000ffffdfff > RDX: 0000000000000000 RSI: 00000000ffffffea RDI: 0000000000000001 > RBP: ffff9e500244d800 R08: 00000000ffffdfff R09: ffff9e6eae1fffa8 > R10: 00000000ffffdfff R11: 0000000000000003 R12: 00007fffc0000000 > R13: 000000000000001f R14: 0000000000000015 R15: ffff9e6eaf180000 > FS: 0000000000000000(0000) GS:ffff9e6eaf180000(0000) > knlGS:0000000000000000 > CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > CR2: 0000000000000000 CR3: 0000000109966000 CR4: 0000000000f50ef0 > PKRU: 55555554 > Call Trace: > <TASK> > tlb_flush_mmu+0x125/0x1a0 > tlb_finish_mmu+0x41/0x80 > relocate_vma_down+0x183/0x200 > setup_arg_pages+0x201/0x390 > load_elf_binary+0x3a7/0x17d0 > bprm_execve+0x244/0x630 > kernel_execve+0x180/0x1f0 > call_usermodehelper_exec_async+0xd0/0x190 > ret_from_fork+0x34/0x50 > ret_from_fork_asm+0x1a/0x30 > </TASK> > > What do I do with it? Reporting it is the right thing. Let me dig into what setup_arg_pages and relocate_vma_down are doing to come up with a 2MB page size area where the end is not 2MB aligned. Reading through the relocate_vma_down code, and the free_pgd/p4d/pud/pmd_range code, it looks like that code always adds PAGE_SIZE to the address being zapped, even when zapping things at a larger granularity. On the flip side, the code in relocate_vma_down and free_pgd_range correctly set the TLB page size to the 4kB PAGE_SIZE. It looks like setting the stride_shift to something larger is done transparently by the x86 tlb_flush() implementation, specifically by tlb_get_unmap_shift(), which looks at which page table level got freed to determine what stride shift to use. This can result in flush_tlb_mm_range being called with a stride_shift for 2MB pages, but a range ending on a 4kB aligned (not 2MB aligned) boundary. Peter, how should we solve this one? Should tlb_flush() round the start & end addresses to match the found stride_shift? -- All Rights Reversed.
