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From: Alan Cox <alc@FreeBSD.org>
Date: Sun, 17 Nov 2019 22:44:39 +0000 (UTC)
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Subject: svn commit: r354799 - stable/12/sys/arm64/arm64
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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)