[PATCH] riscv: mm: execute local TLB flush after populating vmemmap

[Vincent Chen]

The spare_init() calls memmap_populate() many times to create VA to PA
mapping for the VMEMMAP area, where all "strcut page" are located once
CONFIG_SPARSEMEM_VMEMMAP is defined. These "struct page" are later
initialized in the zone_sizes_init() function. However, during this
process, no sfence.vma instruction is executed for this VMEMMAP area.
This omission may cause the hart to fail to perform page table work
because some data related to the address translation is invisible to the
hart. To solve this issue, the local_flush_tlb_kernel_range() is called
right after the spare_init() to execute a sfence.vma instruction for the
VMEMMAP area, ensuring that all data related to the address translation
is visible to the hart.

Fixes: d95f1a542c3d ("RISC-V: Implement sparsemem")
Signed-off-by: Vincent Chen <vincent.chen at sifive.com>
Reviewed-by: Alexandre Ghiti <alexghiti at rivosinc.com>
---
 arch/riscv/include/asm/tlbflush.h | 7 +++++++
 arch/riscv/mm/init.c              | 5 +++++
 2 files changed, 12 insertions(+)

diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
index a09196f8de68..f9d3712bd93b 100644
--- a/arch/riscv/include/asm/tlbflush.h
+++ b/arch/riscv/include/asm/tlbflush.h
@@ -61,4 +61,11 @@ static inline void flush_tlb_kernel_range(unsigned long start,
 	flush_tlb_all();
 }
 
+/* Flush a range of kernel pages without broadcasting */
+static inline void local_flush_tlb_kernel_range(unsigned long start,
+						unsigned long end)
+{
+	local_flush_tlb_all();
+}
+
 #endif /* _ASM_RISCV_TLBFLUSH_H */
diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
index 478d6763a01a..5bd96f6c8f19 100644
--- a/arch/riscv/mm/init.c
+++ b/arch/riscv/mm/init.c
@@ -1231,6 +1231,10 @@ void __init misc_mem_init(void)
 	early_memtest(min_low_pfn << PAGE_SHIFT, max_low_pfn << PAGE_SHIFT);
 	arch_numa_init();
 	sparse_init();
+#ifdef CONFIG_SPARSEMEM_VMEMMAP
+	/* The entire VMEMMAP region has been propulated. Flush TLB for this region */
+	local_flush_tlb_kernel_range(VMEMMAP_START, VMEMMAP_END);
+#endif
 	zone_sizes_init();
 	reserve_crashkernel();
 	memblock_dump_all();
@@ -1240,6 +1244,7 @@ void __init misc_mem_init(void)
 int __meminit vmemmap_populate(unsigned long start, unsigned long end, int node,
 			       struct vmem_altmap *altmap)
 {
+	/* Defer the required TLB flush until the entire VMEMMAP region has been populated */
 	return vmemmap_populate_basepages(start, end, node, NULL);
 }
 #endif
-- 
2.25.1