Revert "arm64: Mark kernel page ranges contiguous"

This reverts commit 348a65cdcbbf243073ee39d1f7d4413081ad7eab.

Incorrect page table manipulation that does not respect the ARM ARM
recommended break-before-make sequence may lead to TLB conflicts. The
contiguous PTE patch makes the system even more susceptible to such
errors by changing the mapping from a single page to a contiguous range
of pages. An additional TLB invalidation would reduce the risk window,
however, the correct fix is to switch to a temporary swapper_pg_dir.
Once the correct workaround is done, the reverted commit will be
re-applied.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Reported-by: Jeremy Linton <jeremy.linton@arm.com>

diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
index 78d91b1eab84876ae06f53c4c8edae625921fcee..873e363048c6c661eda620bbd4f826ba568c5ba7 100644 (file)
--- a/arch/arm64/mm/mmu.c
+++ b/arch/arm64/mm/mmu.c
@@ -85,55 +85,19 @@ static void split_pmd(pmd_t *pmd, pte_t *pte)
        do {
                /*
                 * Need to have the least restrictive permissions available
-                * permissions will be fixed up later. Default the new page
-                * range as contiguous ptes.
+                * permissions will be fixed up later
                 */
-               set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC_CONT));
+               set_pte(pte, pfn_pte(pfn, PAGE_KERNEL_EXEC));
                pfn++;
        } while (pte++, i++, i < PTRS_PER_PTE);
 }
 
-/*
- * Given a PTE with the CONT bit set, determine where the CONT range
- * starts, and clear the entire range of PTE CONT bits.
- */
-static void clear_cont_pte_range(pte_t *pte, unsigned long addr)
-{
-       int i;
-
-       pte -= CONT_RANGE_OFFSET(addr);
-       for (i = 0; i < CONT_PTES; i++) {
-               set_pte(pte, pte_mknoncont(*pte));
-               pte++;
-       }
-       flush_tlb_all();
-}
-
-/*
- * Given a range of PTEs set the pfn and provided page protection flags
- */
-static void __populate_init_pte(pte_t *pte, unsigned long addr,
-                               unsigned long end, phys_addr_t phys,
-                               pgprot_t prot)
-{
-       unsigned long pfn = __phys_to_pfn(phys);
-
-       do {
-               /* clear all the bits except the pfn, then apply the prot */
-               set_pte(pte, pfn_pte(pfn, prot));
-               pte++;
-               pfn++;
-               addr += PAGE_SIZE;
-       } while (addr != end);
-}
-
 static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
-                                 unsigned long end, phys_addr_t phys,
+                                 unsigned long end, unsigned long pfn,
                                  pgprot_t prot,
                                  void *(*alloc)(unsigned long size))
 {
        pte_t *pte;
-       unsigned long next;
 
        if (pmd_none(*pmd) || pmd_sect(*pmd)) {
                pte = alloc(PTRS_PER_PTE * sizeof(pte_t));
@@ -146,27 +110,9 @@ static void alloc_init_pte(pmd_t *pmd, unsigned long addr,
 
        pte = pte_offset_kernel(pmd, addr);
        do {
-               next = min(end, (addr + CONT_SIZE) & CONT_MASK);
-               if (((addr | next | phys) & ~CONT_MASK) == 0) {
-                       /* a block of CONT_PTES  */
-                       __populate_init_pte(pte, addr, next, phys,
-                                           __pgprot(pgprot_val(prot) | PTE_CONT));
-               } else {
-                       /*
-                        * If the range being split is already inside of a
-                        * contiguous range but this PTE isn't going to be
-                        * contiguous, then we want to unmark the adjacent
-                        * ranges, then update the portion of the range we
-                        * are interrested in.
-                        */
-                        clear_cont_pte_range(pte, addr);
-                        __populate_init_pte(pte, addr, next, phys, prot);
-               }
-
-               pte += (next - addr) >> PAGE_SHIFT;
-               phys += next - addr;
-               addr = next;
-       } while (addr != end);
+               set_pte(pte, pfn_pte(pfn, prot));
+               pfn++;
+       } while (pte++, addr += PAGE_SIZE, addr != end);
 }
 
 static void split_pud(pud_t *old_pud, pmd_t *pmd)
@@ -227,7 +173,8 @@ static void alloc_init_pmd(struct mm_struct *mm, pud_t *pud,
                                }
                        }
                } else {
-                       alloc_init_pte(pmd, addr, next, phys, prot, alloc);
+                       alloc_init_pte(pmd, addr, next, __phys_to_pfn(phys),
+                                      prot, alloc);
                }
                phys += next - addr;
        } while (pmd++, addr = next, addr != end);