[PATCH 2/2] riscv: mm: Define DIRECT_MAP_PHYSMEM_END

Vivian Wang
2026-03-09T11:09:51Z

On RISC-V, the actual mappable range of physical address space is
dependent on the current MMU mode i.e. satp_mode (See
Documentation/arch/riscv/vm-layout.rst).

Define the DIRECT_MAP_PHYSMEM_END macro based on the existing virtual
address space layout macros to expose this information to
get_free_mem_region(). Otherwise, it returns a region that couldn't be
mapped, which breaks ZONE_DEVICE.

Cc: <stable@vger.kernel.org> # v6.13+
Tested-by: Han Gao <gaohan@iscas.ac.cn> # SG2044
Signed-off-by: Vivian Wang <wangruikang@iscas.ac.cn>
---
arch/riscv/include/asm/pgtable.h | 10 ++++++++++
1 file changed, 10 insertions(+)

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
index 08d1ca047104..9c92a84e9755 100644
--- a/arch/riscv/include/asm/pgtable.h
+++ b/arch/riscv/include/asm/pgtable.h
@@ -93,6 +93,16 @@
*/
#define vmemmap ((struct page *)VMEMMAP_START - vmemmap_start_pfn)

+/* Needed to limit get_free_mem_region() */
+#if defined(CONFIG_FLATMEM)
+#define DIRECT_MAP_PHYSMEM_END (phys_ram_base + KERN_VIRT_SIZE - 1)
+#elif defined(CONFIG_SPARSEMEM_VMEMMAP)
+#define DIRECT_MAP_PHYSMEM_END \
+ ((vmemmap_start_pfn + VMEMMAP_SIZE / sizeof(struct page)) * PAGE_SIZE - 1)
+#elif defined(CONFIG_SPARSEMEM)
+/* DIRECT_MAP_PHYSMEM_END is not limited by VA space assignment in this case */
+#endif
+
#define PCI_IO_SIZE SZ_16M
#define PCI_IO_END VMEMMAP_START
#define PCI_IO_START (PCI_IO_END - PCI_IO_SIZE)

--
2.53.0