The branch main has been updated by kib:
URL:
https://cgit.FreeBSD.org/src/commit/?id=6eb141a2c4731130bfac670708a8b90f7cdff742
commit 6eb141a2c4731130bfac670708a8b90f7cdff742
Author: Konstantin Belousov <k...@freebsd.org>
AuthorDate: 2025-06-22 03:38:12 +0000
Commit: Konstantin Belousov <k...@freebsd.org>
CommitDate: 2025-07-05 08:36:01 +0000
amd64 pmap: preallocate pt page for pmap_demote_pdpe() in pmap_demote_DMAP()
Allocate the page outside the kernel_pmap locked region with waiting,
and pass it to pmap_demote_pdpe() to use as pt page, instead of panicing
if VM_ALLOC_INTERRUPT failing.
Reviewed by: alc, markj
Tested by: pho
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Differential revision: https://reviews.freebsd.org/D50970
---
sys/amd64/amd64/pmap.c | 43 +++++++++++++++++++++++++++++++++----------
1 file changed, 33 insertions(+), 10 deletions(-)
diff --git a/sys/amd64/amd64/pmap.c b/sys/amd64/amd64/pmap.c
index 2ab8c3b17e22..443273b42f4d 100644
--- a/sys/amd64/amd64/pmap.c
+++ b/sys/amd64/amd64/pmap.c
@@ -1302,7 +1302,7 @@ static bool pmap_demote_pde(pmap_t pmap, pd_entry_t
*pde, vm_offset_t va);
static bool pmap_demote_pde_locked(pmap_t pmap, pd_entry_t *pde,
vm_offset_t va, struct rwlock **lockp);
static bool pmap_demote_pdpe(pmap_t pmap, pdp_entry_t *pdpe,
- vm_offset_t va);
+ vm_offset_t va, vm_page_t m);
static int pmap_enter_2mpage(pmap_t pmap, vm_offset_t va, vm_page_t m,
vm_prot_t prot, struct rwlock **lockp);
static int pmap_enter_pde(pmap_t pmap, vm_offset_t va, pd_entry_t newpde,
@@ -9547,7 +9547,7 @@ pmap_unmapdev(void *p, vm_size_t size)
* Tries to demote a 1GB page mapping.
*/
static bool
-pmap_demote_pdpe(pmap_t pmap, pdp_entry_t *pdpe, vm_offset_t va)
+pmap_demote_pdpe(pmap_t pmap, pdp_entry_t *pdpe, vm_offset_t va, vm_page_t m)
{
pdp_entry_t newpdpe, oldpdpe;
pd_entry_t *firstpde, newpde, *pde;
@@ -9564,12 +9564,19 @@ pmap_demote_pdpe(pmap_t pmap, pdp_entry_t *pdpe,
vm_offset_t va)
oldpdpe = *pdpe;
KASSERT((oldpdpe & (PG_PS | PG_V)) == (PG_PS | PG_V),
("pmap_demote_pdpe: oldpdpe is missing PG_PS and/or PG_V"));
- pdpg = pmap_alloc_pt_page(pmap, va >> PDPSHIFT,
- VM_ALLOC_WIRED | VM_ALLOC_INTERRUPT);
- if (pdpg == NULL) {
- CTR2(KTR_PMAP, "pmap_demote_pdpe: failure for va %#lx"
- " in pmap %p", va, pmap);
- return (false);
+ if (m == NULL) {
+ pdpg = pmap_alloc_pt_page(pmap, va >> PDPSHIFT,
+ VM_ALLOC_WIRED);
+ if (pdpg == NULL) {
+ CTR2(KTR_PMAP,
+ "pmap_demote_pdpe: failure for va %#lx in pmap %p",
+ va, pmap);
+ return (false);
+ }
+ } else {
+ pdpg = m;
+ pdpg->pindex = va >> PDPSHIFT;
+ pmap_pt_page_count_adj(pmap, 1);
}
pdpgpa = VM_PAGE_TO_PHYS(pdpg);
firstpde = (pd_entry_t *)PHYS_TO_DMAP(pdpgpa);
@@ -9779,7 +9786,7 @@ pmap_change_props_locked(vm_offset_t va, vm_size_t size,
vm_prot_t prot,
tmpva += NBPDP;
continue;
}
- if (!pmap_demote_pdpe(kernel_pmap, pdpe, tmpva))
+ if (!pmap_demote_pdpe(kernel_pmap, pdpe, tmpva, NULL))
return (ENOMEM);
}
pde = pmap_pdpe_to_pde(pdpe, tmpva);
@@ -9948,6 +9955,7 @@ pmap_demote_DMAP(vm_paddr_t base, vm_size_t len, bool
invalidate)
{
pdp_entry_t *pdpe;
pd_entry_t *pde;
+ vm_page_t m;
vm_offset_t va;
bool changed;
@@ -9956,17 +9964,28 @@ pmap_demote_DMAP(vm_paddr_t base, vm_size_t len, bool
invalidate)
KASSERT(powerof2(len), ("pmap_demote_DMAP: len is not a power of 2"));
KASSERT((base & (len - 1)) == 0,
("pmap_demote_DMAP: base is not a multiple of len"));
+ WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, NULL, "pmap_demote_DMAP");
+
if (len < NBPDP && base < dmaplimit) {
va = PHYS_TO_DMAP(base);
changed = false;
+
+ /*
+ * Assume that it is fine to sleep there.
+ * The only existing caller of pmap_demote_DMAP() is the
+ * x86_mr_split_dmap() function.
+ */
+ m = vm_page_alloc_noobj(VM_ALLOC_WIRED | VM_ALLOC_WAITOK);
+
PMAP_LOCK(kernel_pmap);
pdpe = pmap_pdpe(kernel_pmap, va);
if ((*pdpe & X86_PG_V) == 0)
panic("pmap_demote_DMAP: invalid PDPE");
if ((*pdpe & PG_PS) != 0) {
- if (!pmap_demote_pdpe(kernel_pmap, pdpe, va))
+ if (!pmap_demote_pdpe(kernel_pmap, pdpe, va, m))
panic("pmap_demote_DMAP: PDPE failed");
changed = true;
+ m = NULL;
}
if (len < NBPDR) {
pde = pmap_pdpe_to_pde(pdpe, va);
@@ -9981,6 +10000,10 @@ pmap_demote_DMAP(vm_paddr_t base, vm_size_t len, bool
invalidate)
if (changed && invalidate)
pmap_invalidate_page(kernel_pmap, va);
PMAP_UNLOCK(kernel_pmap);
+ if (m != NULL) {
+ vm_page_unwire_noq(m);
+ vm_page_free(m);
+ }
}
}
