riscv: Use hugepage mappings for vmemmap

This will allow better TLB utilization and then should be more performant.

Before:

---[ vmemmap start ]---
0xffff8d8002000000-0xffff8d8012000000    0x000000046ec00000       256M PTE .   ..     ..   D A G . . W R V
---[ vmemmap end ]---

After:

---[ vmemmap start ]---
0xffff8d8002000000-0xffff8d8012000000    0x000000046ec00000       256M PMD .   ..     ..   D A G . . W R V
---[ vmemmap end ]---

Signed-off-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20231214132935.212864-1-alexghiti@rivosinc.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index a65937336cdc8840f6f8997f6a320cf97cf31577..f533dd667a83a1f1da03cf882e27630eb4b66d49 100644 (file)
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1387,10 +1387,29 @@ void __init misc_mem_init(void)
 }
 
 #ifdef CONFIG_SPARSEMEM_VMEMMAP
+void __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node,
+                              unsigned long addr, unsigned long next)
+{
+       pmd_set_huge(pmd, virt_to_phys(p), PAGE_KERNEL);
+}
+
+int __meminit vmemmap_check_pmd(pmd_t *pmdp, int node,
+                               unsigned long addr, unsigned long next)
+{
+       vmemmap_verify((pte_t *)pmdp, node, addr, next);
+       return 1;
+}
+
 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
                               struct vmem_altmap *altmap)
 {
-       return vmemmap_populate_basepages(start, end, node, NULL);
+       /*
+        * Note that SPARSEMEM_VMEMMAP is only selected for rv64 and that we
+        * can't use hugepage mappings for 2-level page table because in case of
+        * memory hotplug, we are not able to update all the page tables with
+        * the new PMDs.
+        */
+       return vmemmap_populate_hugepages(start, end, node, NULL);
 }
 #endif