From 60fbdd9e9dc7074d4cd30ada3ba9547d5c007702 Mon Sep 17 00:00:00 2001 From: Rik van Riel Date: Mon, 30 Dec 2024 12:53:02 -0500 Subject: x86/mm: make MMU_GATHER_RCU_TABLE_FREE unconditional Currently x86 uses CONFIG_MMU_GATHER_TABLE_FREE when using paravirt, and not when running on bare metal. There is no real good reason to do things differently for each setup. Make them all the same. After this change, the synchronization between get_user_pages_fast and page table freeing is handled by RCU, which prevents page tables from being reused for other data while get_user_pages_fast is walking them. This allows us to invalidate page tables while other CPUs have interrupts disabled. Signed-off-by: Rik van Riel Suggested-by: Peter Zijlstra --- arch/x86/Kconfig | 2 +- arch/x86/kernel/paravirt.c | 7 +------ 2 files changed, 2 insertions(+), 7 deletions(-) --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -270,7 +270,7 @@ config X86 select HAVE_PCI select HAVE_PERF_REGS select HAVE_PERF_USER_STACK_DUMP - select MMU_GATHER_RCU_TABLE_FREE if PARAVIRT + select MMU_GATHER_RCU_TABLE_FREE select MMU_GATHER_MERGE_VMAS select HAVE_POSIX_CPU_TIMERS_TASK_WORK select HAVE_REGS_AND_STACK_ACCESS_API --- a/arch/x86/kernel/paravirt.c +++ b/arch/x86/kernel/paravirt.c @@ -59,11 +59,6 @@ void __init native_pv_lock_init(void) static_branch_enable(&virt_spin_lock_key); } -static void native_tlb_remove_table(struct mmu_gather *tlb, void *table) -{ - tlb_remove_page(tlb, table); -} - struct static_key paravirt_steal_enabled; struct static_key paravirt_steal_rq_enabled; @@ -191,7 +186,7 @@ struct paravirt_patch_template pv_ops = .mmu.flush_tlb_kernel = native_flush_tlb_global, .mmu.flush_tlb_one_user = native_flush_tlb_one_user, .mmu.flush_tlb_multi = native_flush_tlb_multi, - .mmu.tlb_remove_table = native_tlb_remove_table, + .mmu.tlb_remove_table = tlb_remove_table, .mmu.exit_mmap = paravirt_nop, .mmu.notify_page_enc_status_changed = paravirt_nop,