If we always align the vmemmap start to PAGE_SIZE, there is a
chance that we may end up allocating page-sized vmemmap backing
pages in RAM in the altmap not present case, because a PAGE_SIZE
aligned address is not PMD_SIZE-aligned.
In this patch, we are aligning the vmemmap start address to
PMD_SIZE if altmap is not present. This ensures that a PMD_SIZE
page is always allocated for the vmemmap mapping if altmap is
not present.
If altmap is present, Make sure we align the start vmemmap addr to
PAGE_SIZE so that we calculate the correct start_pfn in altmap
boundary check to decide whether we should use altmap or RAM based
backing memory allocation. Also the address need to be aligned for
set_pte operation. If the start addr is already PMD_SIZE aligned
and with in the altmap boundary then we will try to use a pmd size
altmap mapping else we go for page size mapping.
So if altmap is present, we try to use the maximum number of
altmap pages; otherwise, we allocate a PMD_SIZE RAM page.
Signed-off-by: Donet Tom <donet...@linux.ibm.com>
---
arch/powerpc/mm/book3s64/radix_pgtable.c | 29 +++++++++++++++---------
1 file changed, 18 insertions(+), 11 deletions(-)
diff --git a/arch/powerpc/mm/book3s64/radix_pgtable.c
b/arch/powerpc/mm/book3s64/radix_pgtable.c
index 3d67aee8c8ca..c630cece8ed4 100644
--- a/arch/powerpc/mm/book3s64/radix_pgtable.c
+++ b/arch/powerpc/mm/book3s64/radix_pgtable.c
@@ -1122,18 +1122,25 @@ int __meminit radix__vmemmap_populate(unsigned long
start, unsigned long end, in
pte_t *pte;
/*
- * Make sure we align the start vmemmap addr so that we calculate
- * the correct start_pfn in altmap boundary check to decided whether
- * we should use altmap or RAM based backing memory allocation. Also
- * the address need to be aligned for set_pte operation.
-
- * If the start addr is already PMD_SIZE aligned we will try to use
- * a pmd mapping. We don't want to be too aggressive here beacause
- * that will cause more allocations in RAM. So only if the namespace
- * vmemmap start addr is PMD_SIZE aligned we will use PMD mapping.
+ * If altmap is present, Make sure we align the start vmemmap addr
+ * to PAGE_SIZE so that we calculate the correct start_pfn in
+ * altmap boundary check to decide whether we should use altmap or
+ * RAM based backing memory allocation. Also the address need to be
+ * aligned for set_pte operation. If the start addr is already
+ * PMD_SIZE aligned and with in the altmap boundary then we will
+ * try to use a pmd size altmap mapping else we go for page size
+ * mapping.
+ *
+ * If altmap is not present, align the vmemmap addr to PMD_SIZE and
+ * always allocate a PMD size page for vmemmap backing.
+ *
*/
- start = ALIGN_DOWN(start, PAGE_SIZE);
+ if (altmap)
+ start = ALIGN_DOWN(start, PAGE_SIZE);
+ else
+ start = ALIGN_DOWN(start, PMD_SIZE);
+
for (addr = start; addr < end; addr = next) {
next = pmd_addr_end(addr, end);
@@ -1159,7 +1166,7 @@ int __meminit radix__vmemmap_populate(unsigned long
start, unsigned long end, in
* in altmap block allocation failures, in which case
* we fallback to RAM for vmemmap allocation.
*/
- if (!IS_ALIGNED(addr, PMD_SIZE) || (altmap &&
+ if (altmap && (!IS_ALIGNED(addr, PMD_SIZE) ||
altmap_cross_boundary(altmap, addr, PMD_SIZE))) {
/*
* make sure we don't create altmap mappings
--
2.48.1
