[RFC 2/2] arm64/mm: Reorganize pfn_valid()

Anshuman Khandual
2020-12-22T07:13:30Z

There are multiple instances of pfn_to_section_nr() and __pfn_to_section()
when CONFIG_SPARSEMEM is enabled. This can be just optimized if the memory
section is fetched earlier. Hence bifurcate pfn_valid() into two different
definitions depending on whether CONFIG_SPARSEMEM is enabled. Also replace
the open coded pfn <--> addr conversion with __[pfn|phys]_to_[phys|pfn]().
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 | 36 ++++++++++++++++++++++++++++++------
1 file changed, 30 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index ee23bda00c28..c3387798a3be 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -212,18 +212,25 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
free_area_init(max_zone_pfns);
}

+#ifdef CONFIG_SPARSEMEM
int pfn_valid(unsigned long pfn)
{
- phys_addr_t addr = pfn << PAGE_SHIFT;
+ struct mem_section *ms = __pfn_to_section(pfn);
+ phys_addr_t addr = __pfn_to_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_to_pfn(addr) != pfn)
return 0;

-#ifdef CONFIG_SPARSEMEM
if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
return 0;

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

/*
@@ -235,11 +242,28 @@ int pfn_valid(unsigned long pfn)
* memory sections covering all of hotplug memory including
* both normal and ZONE_DEVIE based.
*/
- if (!early_section(__pfn_to_section(pfn)))
+ if (!early_section(ms))
return 1;
-#endif
+
return memblock_is_map_memory(addr);
}
+#else
+int pfn_valid(unsigned long pfn)
+{
+ phys_addr_t addr = __pfn_to_phys(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_to_pfn(addr) != pfn)
+ return 0;
+
+ return memblock_is_map_memory(addr);
+}
+#endif
EXPORT_SYMBOL(pfn_valid);

static phys_addr_t memory_limit = PHYS_ADDR_MAX;
--
2.20.1