4.20-stable review patch. If anyone has any objections, please let me know.
------------------
From: Dan Williams dan.j.williams@intel.com
commit ba6f508d0ec4adb09f0a939af6d5e19cdfa8667d upstream.
Commit:
f77084d96355 "x86/mm/pat: Disable preemption around __flush_tlb_all()"
addressed a case where __flush_tlb_all() is called without preemption being disabled. It also left a warning to catch other cases where preemption is not disabled.
That warning triggers for the memory hotplug path which is also used for persistent memory enabling:
WARNING: CPU: 35 PID: 911 at ./arch/x86/include/asm/tlbflush.h:460 RIP: 0010:__flush_tlb_all+0x1b/0x3a [..] Call Trace: phys_pud_init+0x29c/0x2bb kernel_physical_mapping_init+0xfc/0x219 init_memory_mapping+0x1a5/0x3b0 arch_add_memory+0x2c/0x50 devm_memremap_pages+0x3aa/0x610 pmem_attach_disk+0x585/0x700 [nd_pmem]
Andy wondered why a path that can sleep was using __flush_tlb_all() [1] and Dave confirmed the expectation for TLB flush is for modifying / invalidating existing PTE entries, but not initial population [2]. Drop the usage of __flush_tlb_all() in phys_{p4d,pud,pmd}_init() on the expectation that this path is only ever populating empty entries for the linear map. Note, at linear map teardown time there is a call to the all-cpu flush_tlb_all() to invalidate the removed mappings.
[1]: https://lkml.kernel.org/r/9DFD717D-857D-493D-A606-B635D72BAC21@amacapital.ne... [2]: https://lkml.kernel.org/r/749919a4-cdb1-48a3-adb4-adb81a5fa0b5@intel.com
[ mingo: Minor readability edits. ]
Suggested-by: Dave Hansen dave.hansen@linux.intel.com Reported-by: Andy Lutomirski luto@kernel.org Signed-off-by: Dan Williams dan.j.williams@intel.com Acked-by: Peter Zijlstra (Intel) peterz@infradead.org Acked-by: Kirill A. Shutemov kirill.shutemov@linux.intel.com Cc: stable@vger.kernel.org Cc: Borislav Petkov bp@alien8.de Cc: H. Peter Anvin hpa@zytor.com Cc: Linus Torvalds torvalds@linux-foundation.org Cc: Peter Zijlstra peterz@infradead.org Cc: Rik van Riel riel@surriel.com Cc: Sebastian Andrzej Siewior bigeasy@linutronix.de Cc: Thomas Gleixner tglx@linutronix.de Cc: dave.hansen@intel.com Fixes: f77084d96355 ("x86/mm/pat: Disable preemption around __flush_tlb_all()") Link: http://lkml.kernel.org/r/154395944713.32119.15611079023837132638.stgit@dwill... Signed-off-by: Ingo Molnar mingo@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/mm/init_64.c | 6 ------ 1 file changed, 6 deletions(-)
--- a/arch/x86/mm/init_64.c +++ b/arch/x86/mm/init_64.c @@ -584,7 +584,6 @@ phys_pud_init(pud_t *pud_page, unsigned paddr_end, page_size_mask, prot); - __flush_tlb_all(); continue; } /* @@ -627,7 +626,6 @@ phys_pud_init(pud_t *pud_page, unsigned pud_populate(&init_mm, pud, pmd); spin_unlock(&init_mm.page_table_lock); } - __flush_tlb_all();
update_page_count(PG_LEVEL_1G, pages);
@@ -668,7 +666,6 @@ phys_p4d_init(p4d_t *p4d_page, unsigned paddr_last = phys_pud_init(pud, paddr, paddr_end, page_size_mask); - __flush_tlb_all(); continue; }
@@ -680,7 +677,6 @@ phys_p4d_init(p4d_t *p4d_page, unsigned p4d_populate(&init_mm, p4d, pud); spin_unlock(&init_mm.page_table_lock); } - __flush_tlb_all();
return paddr_last; } @@ -733,8 +729,6 @@ kernel_physical_mapping_init(unsigned lo if (pgd_changed) sync_global_pgds(vaddr_start, vaddr_end - 1);
- __flush_tlb_all(); - return paddr_last; }