git: 6c1d6d4c7ffd - main - i386: Add a leaf PTP when pmap_enter(psind=1) creates a wired mapping

The branch main has been updated by markj:

URL: https://cgit.FreeBSD.org/src/commit/?id=6c1d6d4c7ffd81d66acd4869cfe596398df301b7

commit 6c1d6d4c7ffd81d66acd4869cfe596398df301b7
Author:     Bojan Novković <bojan.novkovic@fer.hr>
AuthorDate: 2023-10-09 00:32:35 +0000
Commit:     Mark Johnston <markj@FreeBSD.org>
CommitDate: 2023-10-09 00:40:44 +0000

    i386: Add a leaf PTP when pmap_enter(psind=1) creates a wired mapping
    
    Let pmap_enter_pde() create wired mappings.  In particular, allocate a
    leaf PTP for use during demotion.  This is a step towards reverting
    commit 64087fd7f372.
    
    Reviewed by:    alc, kib, markj
    Sponsored by:   Google, Inc. (GSoC 2023)
    MFC after:      2 weeks
    Differential Revision:  https://reviews.freebsd.org/D41635
---
 sys/i386/i386/pmap.c | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/sys/i386/i386/pmap.c b/sys/i386/i386/pmap.c
index 2d19fc51dd53..6b839484e6c5 100644
--- a/sys/i386/i386/pmap.c
+++ b/sys/i386/i386/pmap.c
@@ -3973,12 +3973,11 @@ pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t newpde, u_int flags,
 	struct spglist free;
 	pd_entry_t oldpde, *pde;
 	vm_page_t mt;
+	vm_page_t uwptpg;
 
 	rw_assert(&pvh_global_lock, RA_WLOCKED);
 	KASSERT((newpde & (PG_M | PG_RW)) != PG_RW,
 	    ("pmap_enter_pde: newpde is missing PG_M"));
-	KASSERT(pmap == kernel_pmap || (newpde & PG_W) == 0,
-	    ("pmap_enter_pde: cannot create wired user mapping"));
 	PMAP_LOCK_ASSERT(pmap, MA_OWNED);
 	pde = pmap_pde(pmap, va);
 	oldpde = *pde;
@@ -4028,11 +4027,40 @@ pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t newpde, u_int flags,
 				panic("pmap_enter_pde: trie insert failed");
 		}
 	}
+
+	/*
+	 * Allocate a leaf ptpage for wired userspace pages.
+	 */
+	uwptpg = NULL;
+	if ((newpde & PG_W) != 0 && pmap != kernel_pmap) {
+		uwptpg = vm_page_alloc_noobj(VM_ALLOC_WIRED);
+		if (uwptpg == NULL) {
+			return (KERN_RESOURCE_SHORTAGE);
+		}
+		uwptpg->pindex = va >> PDRSHIFT;
+		if (pmap_insert_pt_page(pmap, uwptpg, true, false)) {
+			vm_page_unwire_noq(uwptpg);
+			vm_page_free(uwptpg);
+			return (KERN_RESOURCE_SHORTAGE);
+		}
+		pmap->pm_stats.resident_count++;
+		uwptpg->ref_count = NPTEPG;
+	}
 	if ((newpde & PG_MANAGED) != 0) {
 		/*
 		 * Abort this mapping if its PV entry could not be created.
 		 */
 		if (!pmap_pv_insert_pde(pmap, va, newpde, flags)) {
+			if (uwptpg != NULL) {
+				mt = pmap_remove_pt_page(pmap, va);
+				KASSERT(mt == uwptpg,
+				    ("removed pt page %p, expected %p", mt,
+				    uwptpg));
+				pmap->pm_stats.resident_count--;
+				uwptpg->ref_count = 1;
+				vm_page_unwire_noq(uwptpg);
+				vm_page_free(uwptpg);
+			}
 			CTR2(KTR_PMAP, "pmap_enter_pde: failure for va %#lx"
 			    " in pmap %p", va, pmap);
 			return (KERN_RESOURCE_SHORTAGE);