Commit a5c93bfe authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'x86-mm-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull x86 mm updates from Ingo Molnar:

 - Put cpumask_test_cpu() check in switch_mm_irqs_off() under
   CONFIG_DEBUG_VM, to micro-optimize the context-switching code (Rik
   van Riel)

 - Add missing details in virtual memory layout (Kirill A. Shutemov)

* tag 'x86-mm-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/mm/tlb: Put cpumask_test_cpu() check in switch_mm_irqs_off() under CONFIG_DEBUG_VM
  x86/mm/doc: Add missing details in virtual memory layout
parents 89c45f38 7e33001b

Documentation/arch/x86/x86_64/mm.rst

+29 −6
Original line number Diff line number Diff line
@@ -29,15 +29,27 @@ Complete virtual memory map with 4-level page tables 
      Start addr    |   Offset   |     End addr     |  Size   | VM area description

  ========================================================================================================================

                    |            |                  |         |

   0000000000000000 |    0       | 00007fffffffffff |  128 TB | user-space virtual memory, different per mm

   0000000000000000 |    0       | 00007fffffffefff | ~128 TB | user-space virtual memory, different per mm

   00007ffffffff000 | ~128    TB | 00007fffffffffff |    4 kB | ... guard hole

  __________________|____________|__________________|_________|___________________________________________________________

                    |            |                  |         |

   0000800000000000 | +128    TB | ffff7fffffffffff | ~16M TB | ... huge, almost 64 bits wide hole of non-canonical

                    |            |                  |         |     virtual memory addresses up to the -128 TB

   0000800000000000 | +128    TB | 7fffffffffffffff |   ~8 EB | ... huge, almost 63 bits wide hole of non-canonical

                    |            |                  |         |     virtual memory addresses up to the -8 EB

                    |            |                  |         |     starting offset of kernel mappings.

                    |            |                  |         |

                    |            |                  |         | LAM relaxes canonicallity check allowing to create aliases

                    |            |                  |         | for userspace memory here.

  __________________|____________|__________________|_________|___________________________________________________________

                                                              |

                                                              | Kernel-space virtual memory, shared between all processes:

  __________________|____________|__________________|_________|___________________________________________________________

                    |            |                  |         |

   8000000000000000 |   -8    EB | ffff7fffffffffff |   ~8 EB | ... huge, almost 63 bits wide hole of non-canonical

                    |            |                  |         |     virtual memory addresses up to the -128 TB

                    |            |                  |         |     starting offset of kernel mappings.

                    |            |                  |         |

                    |            |                  |         | LAM_SUP relaxes canonicallity check allowing to create

                    |            |                  |         | aliases for kernel memory here.

  ____________________________________________________________|___________________________________________________________

                    |            |                  |         |

   ffff800000000000 | -128    TB | ffff87ffffffffff |    8 TB | ... guard hole, also reserved for hypervisor
@@ -88,15 +100,26 @@ Complete virtual memory map with 5-level page tables 
      Start addr    |   Offset   |     End addr     |  Size   | VM area description

  ========================================================================================================================

                    |            |                  |         |

   0000000000000000 |    0       | 00ffffffffffffff |   64 PB | user-space virtual memory, different per mm

   0000000000000000 |    0       | 00fffffffffff000 |  ~64 PB | user-space virtual memory, different per mm

   00fffffffffff000 |  ~64    PB | 00ffffffffffffff |    4 kB | ... guard hole

  __________________|____________|__________________|_________|___________________________________________________________

                    |            |                  |         |

   0100000000000000 |  +64    PB | feffffffffffffff | ~16K PB | ... huge, still almost 64 bits wide hole of non-canonical

                    |            |                  |         |     virtual memory addresses up to the -64 PB

   0100000000000000 |  +64    PB | 7fffffffffffffff |   ~8 EB | ... huge, almost 63 bits wide hole of non-canonical

                    |            |                  |         |     virtual memory addresses up to the -8EB TB

                    |            |                  |         |     starting offset of kernel mappings.

                    |            |                  |         |

                    |            |                  |         | LAM relaxes canonicallity check allowing to create aliases

                    |            |                  |         | for userspace memory here.

  __________________|____________|__________________|_________|___________________________________________________________

                                                              |

                                                              | Kernel-space virtual memory, shared between all processes:

  ____________________________________________________________|___________________________________________________________

   8000000000000000 |   -8    EB | feffffffffffffff |   ~8 EB | ... huge, almost 63 bits wide hole of non-canonical

                    |            |                  |         |     virtual memory addresses up to the -64 PB

                    |            |                  |         |     starting offset of kernel mappings.

                    |            |                  |         |

                    |            |                  |         | LAM_SUP relaxes canonicallity check allowing to create

                    |            |                  |         | aliases for kernel memory here.

  ____________________________________________________________|___________________________________________________________

                    |            |                  |         |

   ff00000000000000 |  -64    PB | ff0fffffffffffff |    4 PB | ... guard hole, also reserved for hypervisor

arch/x86/mm/tlb.c

+1 −1
Original line number Diff line number Diff line
@@ -568,7 +568,7 @@ void switch_mm_irqs_off(struct mm_struct *unused, struct mm_struct *next, 
		 * mm_cpumask. The TLB shootdown code can figure out from

		 * cpu_tlbstate_shared.is_lazy whether or not to send an IPI.

		 */

		if (WARN_ON_ONCE(prev != &init_mm &&

		if (IS_ENABLED(CONFIG_DEBUG_VM) && WARN_ON_ONCE(prev != &init_mm &&

				 !cpumask_test_cpu(cpu, mm_cpumask(next))))

			cpumask_set_cpu(cpu, mm_cpumask(next));