The branch main has been updated by alc:
URL:
https://cgit.FreeBSD.org/src/commit/?id=b87aa791533fd3fc8096faa837264761ed7f4a8c
commit b87aa791533fd3fc8096faa837264761ed7f4a8c
Author: Alan Cox <a...@freebsd.org>
AuthorDate: 2025-07-07 20:29:40 +0000
Commit: Alan Cox <a...@freebsd.org>
CommitDate: 2025-07-14 00:23:49 +0000
amd64 pmap: simplify recent changes to pmap_enter_pde()
When pmap_enter_pde() removes an existing 2MB page mapping within the
kernel address space, do not remap the kernel page table page since it
will shortly be unmapped. Simply zero it.
Eliminate an unnecessary conditional refcount decrement on what must be
a kernel page table page. (We only utilize this refcount on user-space
page table pages.)
Convert an assertion from a panic to a KASSERT.
Reviewed by: kib, markj
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D51235
---
sys/amd64/amd64/pmap.c | 38 +++++++++++++++++++-------------------
1 file changed, 19 insertions(+), 19 deletions(-)
diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index fd02d1ad6690..c3e3a91b20ec 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -1336,7 +1336,7 @@ static pdp_entry_t *pmap_pti_pdpe(vm_offset_t va);
static pd_entry_t *pmap_pti_pde(vm_offset_t va);
static void pmap_pti_wire_pte(void *pte);
static int pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva,
- bool remove_pt, struct spglist *free, struct rwlock **lockp);
+ bool demote_kpde, struct spglist *free, struct rwlock **lockp);
static int pmap_remove_pte(pmap_t pmap, pt_entry_t *ptq, vm_offset_t sva,
pd_entry_t ptepde, struct spglist *free, struct rwlock **lockp);
static vm_page_t pmap_remove_pt_page(pmap_t pmap, vm_offset_t va);
@@ -6165,8 +6165,7 @@ pmap_demote_pde_mpte(pmap_t pmap, pd_entry_t *pde,
vm_offset_t va,
* pmap_remove_kernel_pde: Remove a kernel superpage mapping.
*/
static void
-pmap_remove_kernel_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va,
- bool remove_pt)
+pmap_remove_kernel_pde(pmap_t pmap, pd_entry_t *pde, vm_offset_t va)
{
pd_entry_t newpde;
vm_paddr_t mptepa;
@@ -6174,12 +6173,8 @@ pmap_remove_kernel_pde(pmap_t pmap, pd_entry_t *pde,
vm_offset_t va,
KASSERT(pmap == kernel_pmap, ("pmap %p is not kernel_pmap", pmap));
PMAP_LOCK_ASSERT(pmap, MA_OWNED);
- if (remove_pt)
- mpte = pmap_remove_pt_page(pmap, va);
- else
- mpte = vm_radix_lookup(&pmap->pm_root, pmap_pde_pindex(va));
- if (mpte == NULL)
- panic("pmap_remove_kernel_pde: Missing pt page.");
+ mpte = pmap_remove_pt_page(pmap, va);
+ KASSERT(mpte != NULL, ("pmap_remove_kernel_pde: missing pt page"));
mptepa = VM_PAGE_TO_PHYS(mpte);
newpde = mptepa | X86_PG_M | X86_PG_A | X86_PG_RW | X86_PG_V;
@@ -6209,7 +6204,7 @@ pmap_remove_kernel_pde(pmap_t pmap, pd_entry_t *pde,
vm_offset_t va,
* pmap_remove_pde: do the things to unmap a superpage in a process
*/
static int
-pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva, bool remove_pt,
+pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t sva, bool
demote_kpde,
struct spglist *free, struct rwlock **lockp)
{
struct md_page *pvh;
@@ -6249,9 +6244,7 @@ pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq, vm_offset_t
sva, bool remove_pt,
pmap_delayed_invl_page(m);
}
}
- if (pmap == kernel_pmap) {
- pmap_remove_kernel_pde(pmap, pdq, sva, remove_pt);
- } else {
+ if (pmap != kernel_pmap) {
mpte = pmap_remove_pt_page(pmap, sva);
if (mpte != NULL) {
KASSERT(vm_page_any_valid(mpte),
@@ -6262,6 +6255,14 @@ pmap_remove_pde(pmap_t pmap, pd_entry_t *pdq,
vm_offset_t sva, bool remove_pt,
mpte->ref_count = 0;
pmap_add_delayed_free_list(mpte, free, false);
}
+ } else if (demote_kpde) {
+ pmap_remove_kernel_pde(pmap, pdq, sva);
+ } else {
+ mpte = vm_radix_lookup(&pmap->pm_root, pmap_pde_pindex(sva));
+ if (vm_page_any_valid(mpte)) {
+ mpte->valid = 0;
+ pmap_zero_page(mpte);
+ }
}
return (pmap_unuse_pt(pmap, sva, *pmap_pdpe(pmap, sva), free));
}
@@ -7573,8 +7574,8 @@ pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t
newpde, u_int flags,
* the mapping is not from kernel_pmap, then
* a reserved PT page could be freed.
*/
- (void)pmap_remove_pde(pmap, pde, va,
- pmap != kernel_pmap, &free, lockp);
+ (void)pmap_remove_pde(pmap, pde, va, false, &free,
+ lockp);
if ((oldpde & PG_G) == 0)
pmap_invalidate_pde_page(pmap, va, oldpde);
} else {
@@ -7584,10 +7585,9 @@ pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t
newpde, u_int flags,
* before any changes to mappings are
* made. Abort on failure.
*/
- mt = PHYS_TO_VM_PAGE(*pde & PG_FRAME);
- if (pmap_insert_pt_page(pmap, mt, false,
false)) {
- if (pdpg != NULL)
- pdpg->ref_count--;
+ mt = PHYS_TO_VM_PAGE(oldpde & PG_FRAME);
+ if (pmap_insert_pt_page(pmap, mt, false,
+ false)) {
CTR1(KTR_PMAP,
"pmap_enter_pde: cannot ins kern ptp va %#lx",
va);
