From 8f1d56f64f8d6b80dea2d1978d10071132a695c5 Mon Sep 17 00:00:00 2001 From: Nadav Amit Date: Sun, 10 Jul 2022 16:28:37 -0700 Subject: x86/mm/tlb: Ignore f->new_tlb_gen when zero Commit aa44284960d5 ("x86/mm/tlb: Avoid reading mm_tlb_gen when possible") introduced an optimization to skip superfluous TLB flushes based on the generation provided in flush_tlb_info. However, arch_tlbbatch_flush() does not provide any generation in flush_tlb_info and populates the flush_tlb_info generation with 0. This 0 is causes the flush_tlb_info to be interpreted as a superfluous, old flush. As a result, try_to_unmap_one() would not perform any TLB flushes. Fix it by checking whether f->new_tlb_gen is nonzero. Zero value is anyhow is an invalid generation value. To avoid future confusion, introduce TLB_GENERATION_INVALID constant and use it properly. Add warnings to ensure no partial flushes are done with TLB_GENERATION_INVALID or when f->mm is NULL, since this does not make any sense. In addition, add the missing unlikely(). [ dhansen: change VM_BUG_ON() -> VM_WARN_ON(), clarify changelog ] Fixes: aa44284960d5 ("x86/mm/tlb: Avoid reading mm_tlb_gen when possible") Reported-by: Hugh Dickins Signed-off-by: Nadav Amit Signed-off-by: Dave Hansen Tested-by: Hugh Dickins Link: https://lkml.kernel.org/r/20220710232837.3618-1-namit@vmware.com --- arch/x86/include/asm/tlbflush.h | 1 + 1 file changed, 1 insertion(+) (limited to 'arch/x86/include') diff --git a/arch/x86/include/asm/tlbflush.h b/arch/x86/include/asm/tlbflush.h index 98fa0a114074..21bf105d54f2 100644 --- a/arch/x86/include/asm/tlbflush.h +++ b/arch/x86/include/asm/tlbflush.h @@ -16,6 +16,7 @@ void __flush_tlb_all(void); #define TLB_FLUSH_ALL -1UL +#define TLB_GENERATION_INVALID 0 void cr4_update_irqsoff(unsigned long set, unsigned long clear); unsigned long cr4_read_shadow(void); -- cgit v1.2.3