Re: [PATCH v10 05/10] arm64/vmalloc: allow arch_vmap_pte_range_map_size() to batch multiple CONT_PTE

From: "Barry Song (Xiaomi)" <baohua@kernel.org>

Allow arch_vmap_pte_range_map_size to batch across multiple CONT_PTE
blocks, reducing both PTE setup and TLB flush iterations.

Previously the function returned a single CONT_PTE_SIZE for an aligned
range, so the caller mapped one CONT_PTE block per iteration. Now, for a
CONT_PTE_SIZE-aligned range, it returns the largest CONT_PTE-aligned size
that fits within both the remaining range and the caller's max_page_shift,
so a single pte_set_huge() call installs several CONT_PTE blocks at once.

Signed-off-by: Barry Song (Xiaomi) <baohua@kernel.org>
Signed-off-by: Wen Jiang <redacted>
Tested-by: Xueyuan Chen <redacted>
Tested-by: Leo Yan <leo.yan@arm.com>
---
 arch/arm64/include/asm/vmalloc.h | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/arch/arm64/include/asm/vmalloc.h b/arch/arm64/include/asm/vmalloc.h
index 4ec1acd3c1b34..c29704a19e276 100644
--- a/arch/arm64/include/asm/vmalloc.h
+++ b/arch/arm64/include/asm/vmalloc.h

@@ -23,10 +23,12 @@ static inline unsigned long arch_vmap_pte_range_map_size(unsigned long addr,
 						unsigned long end, u64 pfn,
 						unsigned int max_page_shift)
 {
+	unsigned long size;
+
 	/*
-	 * If the block is at least CONT_PTE_SIZE in size, and is naturally
-	 * aligned in both virtual and physical space, then we can pte-map the
-	 * block using the PTE_CONT bit for more efficient use of the TLB.
+	 * If the range is at least CONT_PTE_SIZE and naturally aligned in both
+	 * virtual and physical space, return the largest CONT_PTE-aligned size
+	 * that fits, for more efficient use of the TLB.
 	 */
 	if (max_page_shift < CONT_PTE_SHIFT)
 		return PAGE_SIZE;

@@ -40,7 +42,9 @@ static inline unsigned long arch_vmap_pte_range_map_size(unsigned long addr,
 	if (!IS_ALIGNED(PFN_PHYS(pfn), CONT_PTE_SIZE))
 		return PAGE_SIZE;
 
-	return CONT_PTE_SIZE;
+	size = min(end - addr, 1UL << max_page_shift);

+	size = round_down(size, CONT_PTE_SIZE);
+	return size;
 }
 
 #define arch_vmap_pte_range_unmap_size arch_vmap_pte_range_unmap_size