riscv: Add a leaf PTP when pmap_enter(psind=1) creates a wired mapping

Let pmap_enter_l2() create wired mappings.  In particular, allocate a
leaf PTP for use during demotion.  This is the last pmap which requires
such a change ahead of reverting commit 64087fd7f372.

Reviewed by:	markj
Sponsored by:	Google, Inc. (GSoC 2023)
MFC after:	2 weeks
Differential Revision:	https://reviews.freebsd.org/D41633

(cherry picked from commit d0941ed9b5c39d92d0aa75bc253506cb59a2e9a1)

1 files changed, 31 insertions, 0 deletions

diff --git a/sys/riscv/riscv/pmap.c b/sys/riscv/riscv/pmap.c
index 8bd5b5e9374d..8ddc31bed81c 100644
--- a/sys/riscv/riscv/pmap.c
+++ b/sys/riscv/riscv/pmap.c
@@ -2679,6 +2679,8 @@ pmap_demote_l2_locked(pmap_t pmap, pd_entry_t *l2, vm_offset_t va,
 	    ("pmap_demote_l2_locked: oldl2 is not a leaf entry"));
 	if ((oldl2 & PTE_A) == 0 || (mpte = pmap_remove_pt_page(pmap, va)) ==
 	    NULL) {
+		KASSERT((oldl2 & PTE_SW_WIRED) == 0,
+		    ("pmap_demote_l2_locked: page table page for a wired mapping is missing"));
 		if ((oldl2 & PTE_A) == 0 || (mpte = vm_page_alloc_noobj(
 		    (VIRT_IN_DMAP(va) ? VM_ALLOC_INTERRUPT : 0) |
 		    VM_ALLOC_WIRED)) == NULL) {
@@ -3211,6 +3213,7 @@ pmap_enter_l2(pmap_t pmap, vm_offset_t va, pd_entry_t new_l2, u_int flags,
 	pd_entry_t *l2, *l3, oldl2;
 	vm_offset_t sva;
 	vm_page_t l2pg, mt;
+	vm_page_t uwptpg;
 
 	PMAP_LOCK_ASSERT(pmap, MA_OWNED);
 
@@ -3268,6 +3271,24 @@ pmap_enter_l2(pmap_t pmap, vm_offset_t va, pd_entry_t new_l2, u_int flags,
 			    ("pmap_enter_l2: non-zero L2 entry %p", l2));
 	}
 
+	/*
+	 * Allocate leaf ptpage for wired userspace pages.
+	 */
+	uwptpg = NULL;
+	if ((new_l2 & PTE_SW_WIRED) != 0 && pmap != kernel_pmap) {
+		uwptpg = vm_page_alloc_noobj(VM_ALLOC_WIRED);
+		if (uwptpg == NULL) {
+			return (KERN_RESOURCE_SHORTAGE);
+		}
+		uwptpg->pindex = pmap_l2_pindex(va);
+		if (pmap_insert_pt_page(pmap, uwptpg, true, false)) {
+			vm_page_unwire_noq(uwptpg);
+			vm_page_free(uwptpg);
+			return (KERN_RESOURCE_SHORTAGE);
+		}
+		pmap_resident_count_inc(pmap, 1);
+		uwptpg->ref_count = Ln_ENTRIES;
+	}
 	if ((new_l2 & PTE_SW_MANAGED) != 0) {
 		/*
 		 * Abort this mapping if its PV entry could not be created.
@@ -3284,6 +3305,16 @@ pmap_enter_l2(pmap_t pmap, vm_offset_t va, pd_entry_t new_l2, u_int flags,
 				pmap_invalidate_page(pmap, va);
 				vm_page_free_pages_toq(&free, true);
 			}
+			if (uwptpg != NULL) {
+				mt = pmap_remove_pt_page(pmap, va);
+				KASSERT(mt == uwptpg,
+				    ("removed pt page %p, expected %p", mt,
+				    uwptpg));
+				pmap_resident_count_dec(pmap, 1);
+				uwptpg->ref_count = 1;
+				vm_page_unwire_noq(uwptpg);
+				vm_page_free(uwptpg);
+			}
 			CTR2(KTR_PMAP,
 			    "pmap_enter_l2: failed to create PV entry"
 			    " for va %#lx in pmap %p", va, pmap);