Adding upstream version 5.10.209.upstream/5.10.209upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 43 insertions, 0 deletions

diff --git a/Documentation/arm64/hugetlbpage.rst b/Documentation/arm64/hugetlbpage.rst
new file mode 100644
index 000000000..a110124c1
--- /dev/null
+++ b/Documentation/arm64/hugetlbpage.rst
@@ -0,0 +1,43 @@
+.. _hugetlbpage_index:
+
+====================
+HugeTLBpage on ARM64
+====================
+
+Hugepage relies on making efficient use of TLBs to improve performance of
+address translations. The benefit depends on both -
+
+  - the size of hugepages
+  - size of entries supported by the TLBs
+
+The ARM64 port supports two flavours of hugepages.
+
+1) Block mappings at the pud/pmd level
+--------------------------------------
+
+These are regular hugepages where a pmd or a pud page table entry points to a
+block of memory. Regardless of the supported size of entries in TLB, block
+mappings reduce the depth of page table walk needed to translate hugepage
+addresses.
+
+2) Using the Contiguous bit
+---------------------------
+
+The architecture provides a contiguous bit in the translation table entries
+(D4.5.3, ARM DDI 0487C.a) that hints to the MMU to indicate that it is one of a
+contiguous set of entries that can be cached in a single TLB entry.
+
+The contiguous bit is used in Linux to increase the mapping size at the pmd and
+pte (last) level. The number of supported contiguous entries varies by page size
+and level of the page table.
+
+
+The following hugepage sizes are supported -
+
+  ====== ========   ====    ========    ===
+  -      CONT PTE    PMD    CONT PMD    PUD
+  ====== ========   ====    ========    ===
+  4K:         64K     2M         32M     1G
+  16K:         2M    32M          1G
+  64K:         2M   512M         16G
+  ====== ========   ====    ========    ===