From 5ad4406f22c558cc84162dbf4baca6fa353a9425 Mon Sep 17 00:00:00 2001
From: kettenis <kettenis@openbsd.org>
Date: Sun, 17 Jul 2022 17:59:35 +0000
Subject: [PATCH] Revert the changes made in rev 1.82.  It is important to use
 pmap_enter(9) and pmap_remove(9) here since we're dealing with managed pages
 here.  Found out the hard way by deraadt@ on landisk where we're running into
 issues with virtual cache aliases because multiple mappings exist for the
 pages we're dealing with here.  The pmap_enter(9) and pmap_remove(9)
 functions handle conflicting cache aliases, whereas pmap_map_direct(9) and
 pmap_kenter_pa(9) assume that the pages is exclusively mapped in the kernel
 pmap.

ok deraadt@
---
 sys/uvm/uvm_pager.c | 30 ++++++++++--------------------
 1 file changed, 10 insertions(+), 20 deletions(-)

diff --git a/sys/uvm/uvm_pager.c b/sys/uvm/uvm_pager.c
index f01df5a3301..6e0ad7552ac 100644
--- a/sys/uvm/uvm_pager.c
+++ b/sys/uvm/uvm_pager.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: uvm_pager.c,v 1.83 2022/07/11 11:33:17 mpi Exp $	*/
+/*	$OpenBSD: uvm_pager.c,v 1.84 2022/07/17 17:59:35 kettenis Exp $	*/
 /*	$NetBSD: uvm_pager.c,v 1.36 2000/11/27 18:26:41 chs Exp $	*/
 
 /*
@@ -258,16 +258,6 @@ uvm_pagermapin(struct vm_page **pps, int npages, int flags)
 	vsize_t size;
 	struct vm_page *pp;
 
-#ifdef __HAVE_PMAP_DIRECT
-	/* use direct mappings for single page */
-	if (npages == 1) {
-		KASSERT(pps[0]);
-		KASSERT(pps[0]->pg_flags & PG_BUSY);
-		kva = pmap_map_direct(pps[0]);
-		return kva;
-	}
-#endif
-
 	prot = PROT_READ;
 	if (flags & UVMPAGER_MAPIN_READ)
 		prot |= PROT_WRITE;
@@ -283,7 +273,14 @@ uvm_pagermapin(struct vm_page **pps, int npages, int flags)
 		pp = *pps++;
 		KASSERT(pp);
 		KASSERT(pp->pg_flags & PG_BUSY);
-		pmap_kenter_pa(cva, VM_PAGE_TO_PHYS(pp), prot);
+		/* Allow pmap_enter to fail. */
+		if (pmap_enter(pmap_kernel(), cva, VM_PAGE_TO_PHYS(pp),
+		    prot, PMAP_WIRED | PMAP_CANFAIL | prot) != 0) {
+			pmap_remove(pmap_kernel(), kva, cva);
+			pmap_update(pmap_kernel());
+			uvm_pseg_release(kva);
+			return 0;
+		}
 	}
 	pmap_update(pmap_kernel());
 	return kva;
@@ -297,15 +294,8 @@ uvm_pagermapin(struct vm_page **pps, int npages, int flags)
 void
 uvm_pagermapout(vaddr_t kva, int npages)
 {
-#ifdef __HAVE_PMAP_DIRECT
-	/* use direct mappings for single page */
-	if (npages == 1) {
-		pmap_unmap_direct(kva);
-		return;
-	}
-#endif
 
-	pmap_kremove(kva, (vsize_t)npages << PAGE_SHIFT);
+	pmap_remove(pmap_kernel(), kva, kva + ((vsize_t)npages << PAGE_SHIFT));
 	pmap_update(pmap_kernel());
 	uvm_pseg_release(kva);
 
-- 
2.20.1