Date: Sun, 17 Nov 2019 22:44:39 +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: r354799 - stable/12/sys/arm64/arm64 Message-ID: <201911172244.xAHMid7U042915@repo.freebsd.org>
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Author: alc Date: Sun Nov 17 22:44:38 2019 New Revision: 354799 URL: https://svnweb.freebsd.org/changeset/base/354799 Log: MFC r352847,352930,354585 Eliminate redundant calls to critical_enter() and critical_exit() from pmap_update_entry(). It suffices that interrupts are blocked. In short, pmap_enter_quick_locked("user space", ..., VM_PROT_READ) doesn't work. More precisely, it doesn't set ATTR_AP(ATTR_AP_USER) in the page table entry, so any attempt to read from the mapped page by user space generates a page fault. This problem has gone unnoticed because the page fault handler, vm_fault(), will ultimately call pmap_enter(), which replaces the non-working page table entry with one that has ATTR_AP(ATTR_AP_USER) set. This change reduces the number of page faults during a "buildworld" by about 19.4%. Eliminate a redundant pmap_load() from pmap_remove_pages(). There is no reason why the pmap_invalidate_all() in pmap_remove_pages() must be performed before the final PV list lock release. Move it past the lock release. Eliminate a stale comment from pmap_page_test_mappings(). We implemented a modified bit in r350004. Modified: stable/12/sys/arm64/arm64/pmap.c Directory Properties: stable/12/ (props changed) Modified: stable/12/sys/arm64/arm64/pmap.c ============================================================================== --- stable/12/sys/arm64/arm64/pmap.c Sun Nov 17 20:56:25 2019 (r354798) +++ stable/12/sys/arm64/arm64/pmap.c Sun Nov 17 22:44:38 2019 (r354799) @@ -3019,7 +3019,6 @@ pmap_update_entry(pmap_t pmap, pd_entry_t *pte, pd_ent * as they may make use of an address we are about to invalidate. */ intr = intr_disable(); - critical_enter(); /* Clear the old mapping */ pmap_clear(pte); @@ -3029,7 +3028,6 @@ pmap_update_entry(pmap_t pmap, pd_entry_t *pte, pd_ent pmap_store(pte, newpte); dsb(ishst); - critical_exit(); intr_restore(intr); } @@ -3763,8 +3761,8 @@ pmap_enter_quick_locked(pmap_t pmap, vm_offset_t va, v ATTR_AP(ATTR_AP_RO) | L3_PAGE; if ((prot & VM_PROT_EXECUTE) == 0 || m->md.pv_memattr == DEVICE_MEMORY) l3_val |= ATTR_XN; - else if (va < VM_MAXUSER_ADDRESS) - l3_val |= ATTR_PXN; + if (va < VM_MAXUSER_ADDRESS) + l3_val |= ATTR_AP(ATTR_AP_USER) | ATTR_PXN; /* * Now validate mapping with RO protection @@ -4330,7 +4328,6 @@ pmap_remove_pages(pmap_t pmap) L2_BLOCK, ("Attempting to remove an invalid " "block: %lx", tpte)); - tpte = pmap_load(pte); break; case 2: pte = pmap_l2_to_l3(pde, pv->pv_va); @@ -4448,17 +4445,15 @@ pmap_remove_pages(pmap_t pmap) free_pv_chunk(pc); } } - pmap_invalidate_all(pmap); if (lock != NULL) rw_wunlock(lock); + pmap_invalidate_all(pmap); PMAP_UNLOCK(pmap); vm_page_free_pages_toq(&free, true); } /* - * This is used to check if a page has been accessed or modified. As we - * don't have a bit to see if it has been modified we have to assume it - * has been if the page is read/write. + * This is used to check if a page has been accessed or modified. */ static boolean_t pmap_page_test_mappings(vm_page_t m, boolean_t accessed, boolean_t modified)
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