x86/mm: remove vmalloc faulting

Remove fault handling on vmalloc areas, as the vmalloc code now takes
care of synchronizing changes to all page-tables in the system.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: "H . Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: Steven Rostedt (VMware) <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vlastimil Babka <vbabka@suse.cz>
Link: http://lkml.kernel.org/r/20200515140023.25469-8-joro@8bytes.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/include/asm/switch_to.h b/arch/x86/include/asm/switch_to.h
index 0e059b7..9f69cc4 100644 (file)
--- a/arch/x86/include/asm/switch_to.h
+++ b/arch/x86/include/asm/switch_to.h
@@ -12,27 +12,6 @@ struct task_struct *__switch_to_asm(struct task_struct *prev,
 __visible struct task_struct *__switch_to(struct task_struct *prev,
                                          struct task_struct *next);
 
-/* This runs runs on the previous thread's stack. */
-static inline void prepare_switch_to(struct task_struct *next)
-{
-#ifdef CONFIG_VMAP_STACK
-       /*
-        * If we switch to a stack that has a top-level paging entry
-        * that is not present in the current mm, the resulting #PF will
-        * will be promoted to a double-fault and we'll panic.  Probe
-        * the new stack now so that vmalloc_fault can fix up the page
-        * tables if needed.  This can only happen if we use a stack
-        * in vmap space.
-        *
-        * We assume that the stack is aligned so that it never spans
-        * more than one top-level paging entry.
-        *
-        * To minimize cache pollution, just follow the stack pointer.
-        */
-       READ_ONCE(*(unsigned char *)next->thread.sp);
-#endif
-}
-
 asmlinkage void ret_from_fork(void);
 
 /*
@@ -67,8 +46,6 @@ struct fork_frame {
 
 #define switch_to(prev, next, last)                                    \
 do {                                                                   \
-       prepare_switch_to(next);                                        \
-                                                                       \
        ((last) = __switch_to_asm((prev), (next)));                     \
 } while (0)
 

diff --git a/arch/x86/kernel/setup_percpu.c b/arch/x86/kernel/setup_percpu.c
index e6d7894..fd945ce 100644 (file)
--- a/arch/x86/kernel/setup_percpu.c
+++ b/arch/x86/kernel/setup_percpu.c
@@ -287,9 +287,9 @@ void __init setup_per_cpu_areas(void)
        /*
         * Sync back kernel address range again.  We already did this in
         * setup_arch(), but percpu data also needs to be available in
-        * the smpboot asm.  We can't reliably pick up percpu mappings
-        * using vmalloc_fault(), because exception dispatch needs
-        * percpu data.
+        * the smpboot asm and arch_sync_kernel_mappings() doesn't sync to
+        * swapper_pg_dir on 32-bit. The per-cpu mappings need to be available
+        * there too.
         *
         * FIXME: Can the later sync in setup_cpu_entry_areas() replace
         * this call?

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index 255fc63..dffe8e4 100644 (file)
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -214,44 +214,6 @@ void arch_sync_kernel_mappings(unsigned long start, unsigned long end)
        }
 }
 
-/*
- * 32-bit:
- *
- *   Handle a fault on the vmalloc or module mapping area
- */
-static noinline int vmalloc_fault(unsigned long address)
-{
-       unsigned long pgd_paddr;
-       pmd_t *pmd_k;
-       pte_t *pte_k;
-
-       /* Make sure we are in vmalloc area: */
-       if (!(address >= VMALLOC_START && address < VMALLOC_END))
-               return -1;
-
-       /*
-        * Synchronize this task's top level page-table
-        * with the 'reference' page table.
-        *
-        * Do _not_ use "current" here. We might be inside
-        * an interrupt in the middle of a task switch..
-        */
-       pgd_paddr = read_cr3_pa();
-       pmd_k = vmalloc_sync_one(__va(pgd_paddr), address);
-       if (!pmd_k)
-               return -1;
-
-       if (pmd_large(*pmd_k))
-               return 0;
-
-       pte_k = pte_offset_kernel(pmd_k, address);
-       if (!pte_present(*pte_k))
-               return -1;
-
-       return 0;
-}
-NOKPROBE_SYMBOL(vmalloc_fault);
-
 /*
  * Did it hit the DOS screen memory VA from vm86 mode?
  */
@@ -316,79 +278,6 @@ out:
 
 #else /* CONFIG_X86_64: */
 
-/*
- * 64-bit:
- *
- *   Handle a fault on the vmalloc area
- */
-static noinline int vmalloc_fault(unsigned long address)
-{
-       pgd_t *pgd, *pgd_k;
-       p4d_t *p4d, *p4d_k;
-       pud_t *pud;
-       pmd_t *pmd;
-       pte_t *pte;
-
-       /* Make sure we are in vmalloc area: */
-       if (!(address >= VMALLOC_START && address < VMALLOC_END))
-               return -1;
-
-       /*
-        * Copy kernel mappings over when needed. This can also
-        * happen within a race in page table update. In the later
-        * case just flush:
-        */
-       pgd = (pgd_t *)__va(read_cr3_pa()) + pgd_index(address);
-       pgd_k = pgd_offset_k(address);
-       if (pgd_none(*pgd_k))
-               return -1;
-
-       if (pgtable_l5_enabled()) {
-               if (pgd_none(*pgd)) {
-                       set_pgd(pgd, *pgd_k);
-                       arch_flush_lazy_mmu_mode();
-               } else {
-                       BUG_ON(pgd_page_vaddr(*pgd) != pgd_page_vaddr(*pgd_k));
-               }
-       }
-
-       /* With 4-level paging, copying happens on the p4d level. */
-       p4d = p4d_offset(pgd, address);
-       p4d_k = p4d_offset(pgd_k, address);
-       if (p4d_none(*p4d_k))
-               return -1;
-
-       if (p4d_none(*p4d) && !pgtable_l5_enabled()) {
-               set_p4d(p4d, *p4d_k);
-               arch_flush_lazy_mmu_mode();
-       } else {
-               BUG_ON(p4d_pfn(*p4d) != p4d_pfn(*p4d_k));
-       }
-
-       BUILD_BUG_ON(CONFIG_PGTABLE_LEVELS < 4);
-
-       pud = pud_offset(p4d, address);
-       if (pud_none(*pud))
-               return -1;
-
-       if (pud_large(*pud))
-               return 0;
-
-       pmd = pmd_offset(pud, address);
-       if (pmd_none(*pmd))
-               return -1;
-
-       if (pmd_large(*pmd))
-               return 0;
-
-       pte = pte_offset_kernel(pmd, address);
-       if (!pte_present(*pte))
-               return -1;
-
-       return 0;
-}
-NOKPROBE_SYMBOL(vmalloc_fault);
-
 #ifdef CONFIG_CPU_SUP_AMD
 static const char errata93_warning[] =
 KERN_ERR 
@@ -1227,29 +1116,6 @@ do_kern_addr_fault(struct pt_regs *regs, unsigned long hw_error_code,
         */
        WARN_ON_ONCE(hw_error_code & X86_PF_PK);
 
-       /*
-        * We can fault-in kernel-space virtual memory on-demand. The
-        * 'reference' page table is init_mm.pgd.
-        *
-        * NOTE! We MUST NOT take any locks for this case. We may
-        * be in an interrupt or a critical region, and should
-        * only copy the information from the master page table,
-        * nothing more.
-        *
-        * Before doing this on-demand faulting, ensure that the
-        * fault is not any of the following:
-        * 1. A fault on a PTE with a reserved bit set.
-        * 2. A fault caused by a user-mode access.  (Do not demand-
-        *    fault kernel memory due to user-mode accesses).
-        * 3. A fault caused by a page-level protection violation.
-        *    (A demand fault would be on a non-present page which
-        *     would have X86_PF_PROT==0).
-        */
-       if (!(hw_error_code & (X86_PF_RSVD | X86_PF_USER | X86_PF_PROT))) {
-               if (vmalloc_fault(address) >= 0)
-                       return;
-       }
-
        /* Was the fault spurious, caused by lazy TLB invalidation? */
        if (spurious_kernel_fault(hw_error_code, address))
                return;

diff --git a/arch/x86/mm/pti.c b/arch/x86/mm/pti.c
index 843aa10..da0fb17 100644 (file)
--- a/arch/x86/mm/pti.c
+++ b/arch/x86/mm/pti.c
@@ -448,13 +448,7 @@ static void __init pti_clone_user_shared(void)
                 * the sp1 and sp2 slots.
                 *
                 * This is done for all possible CPUs during boot to ensure
-                * that it's propagated to all mms.  If we were to add one of
-                * these mappings during CPU hotplug, we would need to take
-                * some measure to make sure that every mm that subsequently
-                * ran on that CPU would have the relevant PGD entry in its
-                * pagetables.  The usual vmalloc_fault() mechanism would not
-                * work for page faults taken in entry_SYSCALL_64 before RSP
-                * is set up.
+                * that it's propagated to all mms.
                 */
 
                unsigned long va = (unsigned long)&per_cpu(cpu_tss_rw, cpu);

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 66f96f2..f3fe261 100644 (file)
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -161,34 +161,6 @@ void switch_mm(struct mm_struct *prev, struct mm_struct *next,
        local_irq_restore(flags);
 }
 
-static void sync_current_stack_to_mm(struct mm_struct *mm)
-{
-       unsigned long sp = current_stack_pointer;
-       pgd_t *pgd = pgd_offset(mm, sp);
-
-       if (pgtable_l5_enabled()) {
-               if (unlikely(pgd_none(*pgd))) {
-                       pgd_t *pgd_ref = pgd_offset_k(sp);
-
-                       set_pgd(pgd, *pgd_ref);
-               }
-       } else {
-               /*
-                * "pgd" is faked.  The top level entries are "p4d"s, so sync
-                * the p4d.  This compiles to approximately the same code as
-                * the 5-level case.
-                */
-               p4d_t *p4d = p4d_offset(pgd, sp);
-
-               if (unlikely(p4d_none(*p4d))) {
-                       pgd_t *pgd_ref = pgd_offset_k(sp);
-                       p4d_t *p4d_ref = p4d_offset(pgd_ref, sp);
-
-                       set_p4d(p4d, *p4d_ref);
-               }
-       }
-}
-
 static inline unsigned long mm_mangle_tif_spec_ib(struct task_struct *next)
 {
        unsigned long next_tif = task_thread_info(next)->flags;
@@ -377,15 +349,6 @@ void switch_mm_irqs_off(struct mm_struct *prev, struct mm_struct *next,
                 */
                cond_ibpb(tsk);
 
-               if (IS_ENABLED(CONFIG_VMAP_STACK)) {
-                       /*
-                        * If our current stack is in vmalloc space and isn't
-                        * mapped in the new pgd, we'll double-fault.  Forcibly
-                        * map it.
-                        */
-                       sync_current_stack_to_mm(next);
-               }
-
                /*
                 * Stop remote flushes for the previous mm.
                 * Skip kernel threads; we never send init_mm TLB flushing IPIs,