diff --git a/sys/riscv/riscv/pmap.c b/sys/riscv/riscv/pmap.c --- a/sys/riscv/riscv/pmap.c +++ b/sys/riscv/riscv/pmap.c @@ -872,7 +872,7 @@ vm_paddr_t pmap_kextract(vm_offset_t va) { - pd_entry_t *l2; + pd_entry_t *l2, l2e; pt_entry_t *l3; vm_paddr_t pa; @@ -882,14 +882,23 @@ l2 = pmap_l2(kernel_pmap, va); if (l2 == NULL) panic("pmap_kextract: No l2"); - if ((pmap_load(l2) & PTE_RX) != 0) { + l2e = pmap_load(l2); + /* + * Beware of concurrent promotion and demotion! We must + * use l2e rather than loading from l2 multiple times to + * ensure we see a consistent state, including the + * implicit load in pmap_l2_to_l3. It is, however, safe + * to use an old l2e because the L3 page is preserved by + * promotion. + */ + if ((l2e & PTE_RX) != 0) { /* superpages */ - pa = L2PTE_TO_PHYS(pmap_load(l2)); + pa = L2PTE_TO_PHYS(l2e); pa |= (va & L2_OFFSET); return (pa); } - l3 = pmap_l2_to_l3(l2, va); + l3 = pmap_l2_to_l3(&l2e, va); if (l3 == NULL) panic("pmap_kextract: No l3..."); pa = PTE_TO_PHYS(pmap_load(l3));