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Subject[PATCH] riscv: Use hugepage mappings for vmemmap
Date
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>
---
arch/riscv/mm/init.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 2e011cbddf3a..f636336e6401 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1383,10 +1383,29 @@ 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

--
2.39.2
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