[PATCH] arm64/hugetlb: Reserve CMA areas for gigantic pages on 16K and 64K configs

Anshuman Khandual
2020-06-23T06:22:10Z

Currently 'hugetlb_cma=' command line argument does not create CMA area on
ARM64_16K_PAGES and ARM64_64K_PAGES based platforms. Instead, it just ends
up with the following warning message. Reason being, hugetlb_cma_reserve()
never gets called for these huge page sizes.

[ 64.255669] hugetlb_cma: the option isn't supported by current arch

This enables CMA areas reservation on ARM64_16K_PAGES and ARM64_64K_PAGES
configs by defining an unified arm64_hugetlb_cma_reseve() that is wrapped
in CONFIG_CMA.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Barry Song <song.bao.hua@hisilicon.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
---
Applies on 5.8-rc2.

arch/arm64/include/asm/hugetlb.h | 8 ++++++++
arch/arm64/mm/hugetlbpage.c | 38 ++++++++++++++++++++++++++++++++++++++
arch/arm64/mm/init.c | 4 +---
3 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/arch/arm64/include/asm/hugetlb.h b/arch/arm64/include/asm/hugetlb.h
index 94ba0c5..8eea0e0 100644
--- a/arch/arm64/include/asm/hugetlb.h
+++ b/arch/arm64/include/asm/hugetlb.h
@@ -17,6 +17,14 @@
extern bool arch_hugetlb_migration_supported(struct hstate *h);
#endif

+#ifdef CONFIG_CMA
+void arm64_hugetlb_cma_reserve(void);
+#else
+static inline void arm64_hugetlb_cma_reserve(void)
+{
+}
+#endif
+
static inline void arch_clear_hugepage_flags(struct page *page)
{
clear_bit(PG_dcache_clean, &page->flags);
diff --git a/arch/arm64/mm/hugetlbpage.c b/arch/arm64/mm/hugetlbpage.c
index 0a52ce4..ea7fb48 100644
--- a/arch/arm64/mm/hugetlbpage.c
+++ b/arch/arm64/mm/hugetlbpage.c
@@ -19,6 +19,44 @@
#include <asm/tlbflush.h>
#include <asm/pgalloc.h>

+/*
+ * HugeTLB Support Matrix
+ *
+ * ---------------------------------------------------
+ * | Page Size | CONT PTE | PMD | CONT PMD | PUD |
+ * ---------------------------------------------------
+ * | 4K | 64K | 2M | 32M | 1G |
+ * | 16K | 2M | 32M | 1G | |
+ * | 64K | 2M | 512M | 16G | |
+ * ---------------------------------------------------
+ */
+
+/*
+ * Reserve CMA areas for the largest supported gigantic
+ * huge page when requested. Any other smaller gigantic
+ * huge pages could still be served from those areas.
+ */
+#ifdef CONFIG_CMA
+void __init arm64_hugetlb_cma_reserve(void)
+{
+ int order;
+
+#ifdef CONFIG_ARM64_4K_PAGES
+ order = PUD_SHIFT - PAGE_SHIFT;
+#else
+ order = CONT_PMD_SHIFT + PMD_SHIFT - PAGE_SHIFT;
+#endif
+ /*
+ * HugeTLB CMA reservation is required for gigantic
+ * huge pages which could not be allocated via the
+ * page allocator. Just warn if there is any change
+ * breaking this assumption.
+ */
+ WARN_ON(order <= MAX_ORDER);
+ hugetlb_cma_reserve(order);
+}
+#endif /* CONFIG_CMA */
+
#ifdef CONFIG_ARCH_ENABLE_HUGEPAGE_MIGRATION
bool arch_hugetlb_migration_supported(struct hstate *h)
{
diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
index 1e93cfc..fabf8b0 100644
--- a/arch/arm64/mm/init.c
+++ b/arch/arm64/mm/init.c
@@ -425,9 +425,7 @@ void __init bootmem_init(void)
* initialize node_online_map that gets used in hugetlb_cma_reserve()
* while allocating required CMA size across online nodes.
*/
-#ifdef CONFIG_ARM64_4K_PAGES
- hugetlb_cma_reserve(PUD_SHIFT - PAGE_SHIFT);
-#endif
+ arm64_hugetlb_cma_reserve();

/*
* Sparsemem tries to allocate bootmem in memory_present(), so must be
--
2.7.4