On Fri, Nov 30, 2018 at 04:35:32PM -0800, Dan Williams wrote:
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://lore.kernel.org/lkml/[email protected] [2]: https://lore.kernel.org/lkml/[email protected] Fixes: f77084d96355 ("x86/mm/pat: Disable preemption around __flush_tlb_all()") Cc: Kirill A. Shutemov <[email protected]> Cc: Sebastian Andrzej Siewior <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: <[email protected]> Reported-by: Andy Lutomirski <[email protected]> Suggested-by: Dave Hansen <[email protected]> Signed-off-by: Dan Williams <[email protected]>
Hi Dan, This patch on it's own doesn't apply to any of the stable trees, does it maybe depend on some of the previous patches in this series? -- Thanks, Sasha
