Date: Thu, 19 Sep 2019 15:12:32 +0000 (UTC) From: Alan Cox <alc@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-12@freebsd.org Subject: svn commit: r352519 - in stable/12/sys: amd64/amd64 arm64/arm64 i386/i386 riscv/riscv Message-ID: <201909191512.x8JFCW3H035578@repo.freebsd.org>
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Author: alc Date: Thu Sep 19 15:12:32 2019 New Revision: 352519 URL: https://svnweb.freebsd.org/changeset/base/352519 Log: MFC r350335: Simplify the handling of superpages in pmap_clear_modify(). Specifically, if a demotion succeeds, then all of the 4KB page mappings within the superpage-sized region must be valid, so there is no point in testing the validity of the 4KB page mapping that is going to be write protected. Deindent the nearby code. Modified: stable/12/sys/amd64/amd64/pmap.c stable/12/sys/arm64/arm64/pmap.c stable/12/sys/i386/i386/pmap.c stable/12/sys/riscv/riscv/pmap.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/amd64/amd64/pmap.c ============================================================================== --- stable/12/sys/amd64/amd64/pmap.c Thu Sep 19 14:45:04 2019 (r352518) +++ stable/12/sys/amd64/amd64/pmap.c Thu Sep 19 15:12:32 2019 (r352519) @@ -7599,7 +7599,7 @@ pmap_clear_modify(vm_page_t m) pmap_t pmap; pv_entry_t next_pv, pv; pd_entry_t oldpde, *pde; - pt_entry_t oldpte, *pte, PG_M, PG_RW, PG_V; + pt_entry_t *pte, PG_M, PG_RW; struct rwlock *lock; vm_offset_t va; int md_gen, pvh_gen; @@ -7635,33 +7635,23 @@ restart: } } PG_M = pmap_modified_bit(pmap); - PG_V = pmap_valid_bit(pmap); PG_RW = pmap_rw_bit(pmap); va = pv->pv_va; pde = pmap_pde(pmap, va); oldpde = *pde; - if ((oldpde & PG_RW) != 0) { - if (pmap_demote_pde_locked(pmap, pde, va, &lock)) { - if ((oldpde & PG_W) == 0) { - /* - * Write protect the mapping to a - * single page so that a subsequent - * write access may repromote. - */ - va += VM_PAGE_TO_PHYS(m) - (oldpde & - PG_PS_FRAME); - pte = pmap_pde_to_pte(pde, va); - oldpte = *pte; - if ((oldpte & PG_V) != 0) { - while (!atomic_cmpset_long(pte, - oldpte, - oldpte & ~(PG_M | PG_RW))) - oldpte = *pte; - vm_page_dirty(m); - pmap_invalidate_page(pmap, va); - } - } - } + /* If oldpde has PG_RW set, then it also has PG_M set. */ + if ((oldpde & PG_RW) != 0 && + pmap_demote_pde_locked(pmap, pde, va, &lock) && + (oldpde & PG_W) == 0) { + /* + * Write protect the mapping to a single page so that + * a subsequent write access may repromote. + */ + va += VM_PAGE_TO_PHYS(m) - (oldpde & PG_PS_FRAME); + pte = pmap_pde_to_pte(pde, va); + atomic_clear_long(pte, PG_M | PG_RW); + vm_page_dirty(m); + pmap_invalidate_page(pmap, va); } PMAP_UNLOCK(pmap); } Modified: stable/12/sys/arm64/arm64/pmap.c ============================================================================== --- stable/12/sys/arm64/arm64/pmap.c Thu Sep 19 14:45:04 2019 (r352518) +++ stable/12/sys/arm64/arm64/pmap.c Thu Sep 19 15:12:32 2019 (r352519) @@ -5008,28 +5008,22 @@ restart: va = pv->pv_va; l2 = pmap_l2(pmap, va); oldl2 = pmap_load(l2); - if ((oldl2 & ATTR_SW_DBM) != 0) { - if (pmap_demote_l2_locked(pmap, l2, va, &lock)) { - if ((oldl2 & ATTR_SW_WIRED) == 0) { - /* - * Write protect the mapping to a - * single page so that a subsequent - * write access may repromote. - */ - va += VM_PAGE_TO_PHYS(m) - - (oldl2 & ~ATTR_MASK); - l3 = pmap_l2_to_l3(l2, va); - oldl3 = pmap_load(l3); - if (pmap_l3_valid(oldl3)) { - while (!atomic_fcmpset_long(l3, - &oldl3, (oldl3 & ~ATTR_SW_DBM) | - ATTR_AP(ATTR_AP_RO))) - cpu_spinwait(); - vm_page_dirty(m); - pmap_invalidate_page(pmap, va); - } - } - } + /* If oldl2 has ATTR_SW_DBM set, then it is also dirty. */ + if ((oldl2 & ATTR_SW_DBM) != 0 && + pmap_demote_l2_locked(pmap, l2, va, &lock) && + (oldl2 & ATTR_SW_WIRED) == 0) { + /* + * Write protect the mapping to a single page so that + * a subsequent write access may repromote. + */ + va += VM_PAGE_TO_PHYS(m) - (oldl2 & ~ATTR_MASK); + l3 = pmap_l2_to_l3(l2, va); + oldl3 = pmap_load(l3); + while (!atomic_fcmpset_long(l3, &oldl3, + (oldl3 & ~ATTR_SW_DBM) | ATTR_AP(ATTR_AP_RO))) + cpu_spinwait(); + vm_page_dirty(m); + pmap_invalidate_page(pmap, va); } PMAP_UNLOCK(pmap); } Modified: stable/12/sys/i386/i386/pmap.c ============================================================================== --- stable/12/sys/i386/i386/pmap.c Thu Sep 19 14:45:04 2019 (r352518) +++ stable/12/sys/i386/i386/pmap.c Thu Sep 19 15:12:32 2019 (r352519) @@ -5366,7 +5366,7 @@ pmap_clear_modify(vm_page_t m) pv_entry_t next_pv, pv; pmap_t pmap; pd_entry_t oldpde, *pde; - pt_entry_t oldpte, *pte; + pt_entry_t *pte; vm_offset_t va; KASSERT((m->oflags & VPO_UNMANAGED) == 0, @@ -5393,33 +5393,24 @@ pmap_clear_modify(vm_page_t m) PMAP_LOCK(pmap); pde = pmap_pde(pmap, va); oldpde = *pde; - if ((oldpde & PG_RW) != 0) { - if (pmap_demote_pde(pmap, pde, va)) { - if ((oldpde & PG_W) == 0) { - /* - * Write protect the mapping to a - * single page so that a subsequent - * write access may repromote. - */ - va += VM_PAGE_TO_PHYS(m) - (oldpde & - PG_PS_FRAME); - pte = pmap_pte_quick(pmap, va); - oldpte = *pte; - if ((oldpte & PG_V) != 0) { - /* - * Regardless of whether a pte is 32 or 64 bits - * in size, PG_RW and PG_M are among the least - * significant 32 bits. - */ - while (!atomic_cmpset_int((u_int *)pte, - oldpte, - oldpte & ~(PG_M | PG_RW))) - oldpte = *pte; - vm_page_dirty(m); - pmap_invalidate_page(pmap, va); - } - } - } + /* If oldpde has PG_RW set, then it also has PG_M set. */ + if ((oldpde & PG_RW) != 0 && + pmap_demote_pde(pmap, pde, va) && + (oldpde & PG_W) == 0) { + /* + * Write protect the mapping to a single page so that + * a subsequent write access may repromote. + */ + va += VM_PAGE_TO_PHYS(m) - (oldpde & PG_PS_FRAME); + pte = pmap_pte_quick(pmap, va); + /* + * Regardless of whether a pte is 32 or 64 bits + * in size, PG_RW and PG_M are among the least + * significant 32 bits. + */ + atomic_clear_int((u_int *)pte, PG_M | PG_RW); + vm_page_dirty(m); + pmap_invalidate_page(pmap, va); } PMAP_UNLOCK(pmap); } Modified: stable/12/sys/riscv/riscv/pmap.c ============================================================================== --- stable/12/sys/riscv/riscv/pmap.c Thu Sep 19 14:45:04 2019 (r352518) +++ stable/12/sys/riscv/riscv/pmap.c Thu Sep 19 15:12:32 2019 (r352519) @@ -4104,7 +4104,7 @@ pmap_clear_modify(vm_page_t m) pmap_t pmap; pv_entry_t next_pv, pv; pd_entry_t *l2, oldl2; - pt_entry_t *l3, oldl3; + pt_entry_t *l3; vm_offset_t va; int md_gen, pvh_gen; @@ -4142,28 +4142,19 @@ restart: va = pv->pv_va; l2 = pmap_l2(pmap, va); oldl2 = pmap_load(l2); - if ((oldl2 & PTE_W) != 0) { - if (pmap_demote_l2_locked(pmap, l2, va, &lock)) { - if ((oldl2 & PTE_SW_WIRED) == 0) { - /* - * Write protect the mapping to a - * single page so that a subsequent - * write access may repromote. - */ - va += VM_PAGE_TO_PHYS(m) - - PTE_TO_PHYS(oldl2); - l3 = pmap_l2_to_l3(l2, va); - oldl3 = pmap_load(l3); - if ((oldl3 & PTE_V) != 0) { - while (!atomic_fcmpset_long(l3, - &oldl3, oldl3 & ~(PTE_D | - PTE_W))) - cpu_spinwait(); - vm_page_dirty(m); - pmap_invalidate_page(pmap, va); - } - } - } + /* If oldl2 has PTE_W set, then it also has PTE_D set. */ + if ((oldl2 & PTE_W) != 0 && + pmap_demote_l2_locked(pmap, l2, va, &lock) && + (oldl2 & PTE_SW_WIRED) == 0) { + /* + * Write protect the mapping to a single page so that + * a subsequent write access may repromote. + */ + va += VM_PAGE_TO_PHYS(m) - PTE_TO_PHYS(oldl2); + l3 = pmap_l2_to_l3(l2, va); + pmap_clear_bits(l3, PTE_D | PTE_W); + vm_page_dirty(m); + pmap_invalidate_page(pmap, va); } PMAP_UNLOCK(pmap); }
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