[PATCH V2 2/2] arm64/mm: Reorganize pfn_valid()

Anshuman Khandual
2021-02-02T04:12:49Z

There are multiple instances of pfn_to_section_nr() and __pfn_to_section()
when CONFIG_SPARSEMEM is enabled. This can be optimized if memory section
is fetched earlier. This replaces the open coded PFN and ADDR conversion
with PFN_PHYS() and PHYS_PFN() helpers. While there, also add a comment.
This does not cause any functional change.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
arch/arm64/mm/init.c | 20 +++++++++++++++-----
1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 1141075e4d53..5d8fd5360a68 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -219,16 +219,25 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)

int pfn_valid(unsigned long pfn)
{
- phys_addr_t addr = pfn << PAGE_SHIFT;
+ phys_addr_t addr = PFN_PHYS(pfn);

- if ((addr >> PAGE_SHIFT) != pfn)
+ /*
+ * Ensure the upper PAGE_SHIFT bits are clear in the
+ * pfn. Else it might lead to false positives when
+ * some of the upper bits are set, but the lower bits
+ * match a valid pfn.
+ */
+ if (PHYS_PFN(addr) != pfn)
return 0;

#ifdef CONFIG_SPARSEMEM
+{
+ struct mem_section *ms = __pfn_to_section(pfn);
+
if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
return 0;

- if (!valid_section(__pfn_to_section(pfn)))
+ if (!valid_section(ms))
return 0;

/*
@@ -240,8 +249,9 @@ int pfn_valid(unsigned long pfn)
* memory sections covering all of hotplug memory including
* both normal and ZONE_DEVICE based.
*/
- if (!early_section(__pfn_to_section(pfn)))
- return pfn_section_valid(__pfn_to_section(pfn), pfn);
+ if (!early_section(ms))
+ return pfn_section_valid(ms, pfn);
+}
#endif
return memblock_is_map_memory(addr);
}
--
2.20.1