The branch stable/13 has been updated by mhorne: URL: https://cgit.FreeBSD.org/src/commit/?id=ce82d6846bda5378d91aa94c442f9b8c416ffce9
commit ce82d6846bda5378d91aa94c442f9b8c416ffce9 Author: Mitchell Horne <[email protected]> AuthorDate: 2022-10-05 16:14:36 +0000 Commit: Mitchell Horne <[email protected]> CommitDate: 2022-10-13 14:05:21 +0000 riscv: handle kernel PTE edge-case in pmap_enter_l2() Page table pages are never freed from the kernel pmap, instead they are zeroed when a range is unmapped. This allows future mappings to be constructed more quickly. Detect this scenario in pmap_enter_l2(), so we don't fail to create a superpage mapping when the 2MB range is actually available. Reviewed by: markj MFC after: 1 week Sponsored by: The FreeBSD Foundation Differential Revision: https://reviews.freebsd.org/D36885 (cherry picked from commit 1f9cc5ffc50523498545b6f7d50406feb18903be) --- sys/riscv/riscv/pmap.c | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) diff --git a/sys/riscv/riscv/pmap.c b/sys/riscv/riscv/pmap.c index a3a26a8a883d..df473acef0e7 100644 --- a/sys/riscv/riscv/pmap.c +++ b/sys/riscv/riscv/pmap.c @@ -3146,6 +3146,24 @@ pmap_enter_2mpage(pmap_t pmap, vm_offset_t va, vm_page_t m, vm_prot_t prot, PMAP_ENTER_NOREPLACE | PMAP_ENTER_NORECLAIM, NULL, lockp)); } +/* + * Returns true if every page table entry in the specified page table is + * zero. + */ +static bool +pmap_every_pte_zero(vm_paddr_t pa) +{ + pt_entry_t *pt_end, *pte; + + KASSERT((pa & PAGE_MASK) == 0, ("pa is misaligned")); + pte = (pt_entry_t *)PHYS_TO_DMAP(pa); + for (pt_end = pte + Ln_ENTRIES; pte < pt_end; pte++) { + if (*pte != 0) + return (false); + } + return (true); +} + /* * Tries to create the specified 2MB page mapping. Returns KERN_SUCCESS if * the mapping was created, and one of KERN_FAILURE, KERN_NO_SPACE, or @@ -3190,7 +3208,8 @@ pmap_enter_l2(pmap_t pmap, vm_offset_t va, pd_entry_t new_l2, u_int flags, "pmap_enter_l2: no space for va %#lx" " in pmap %p", va, pmap); return (KERN_NO_SPACE); - } else { + } else if (va < VM_MAXUSER_ADDRESS || + !pmap_every_pte_zero(L2PTE_TO_PHYS(oldl2))) { l2pg->ref_count--; CTR2(KTR_PMAP, "pmap_enter_l2:" " failed to replace existing mapping"
