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Date: Fri, 3 Jul 2020 15:39:14 +0200
From: David Hildenbrand <david@...hat.com>
To: linux-kernel@...r.kernel.org
Cc: linux-s390@...r.kernel.org, linux-mm@...ck.org,
David Hildenbrand <david@...hat.com>,
Heiko Carstens <heiko.carstens@...ibm.com>,
Vasily Gorbik <gor@...ux.ibm.com>,
Christian Borntraeger <borntraeger@...ibm.com>,
Gerald Schaefer <gerald.schaefer@...ibm.com>
Subject: [PATCH v1 6/9] s390/vmem: cleanup empty page tables
Let's cleanup empty page tables. Consider only page tables that fully
fall into the idendity mapping and the vmemmap range.
As there are no valid accesses to vmem/vmemmap within non-populated ranges,
the single tlb flush at the end should be sufficient.
Cc: Heiko Carstens <heiko.carstens@...ibm.com>
Cc: Vasily Gorbik <gor@...ux.ibm.com>
Cc: Christian Borntraeger <borntraeger@...ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@...ibm.com>
Signed-off-by: David Hildenbrand <david@...hat.com>
---
arch/s390/mm/vmem.c | 98 ++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 97 insertions(+), 1 deletion(-)
diff --git a/arch/s390/mm/vmem.c b/arch/s390/mm/vmem.c
index aa968f67d7f9f..5239130770b7b 100644
--- a/arch/s390/mm/vmem.c
+++ b/arch/s390/mm/vmem.c
@@ -63,6 +63,15 @@ pte_t __ref *vmem_pte_alloc(void)
return pte;
}
+static void vmem_pte_free(unsigned long *table)
+{
+ /* We don't expect boot memory to be removed ever. */
+ if (!slab_is_available() ||
+ WARN_ON_ONCE(PageReserved(virt_to_page(table))))
+ return;
+ page_table_free(&init_mm, table);
+}
+
/*
* Add a physical memory range to the 1:1 mapping.
*/
@@ -168,6 +177,21 @@ static void remove_pte_table(pmd_t *pmd, unsigned long addr,
update_page_count(PG_DIRECT_MAP_4K, -pages);
}
+static void try_free_pte_table(pmd_t *pmd, unsigned long start)
+{
+ pte_t *pte;
+ int i;
+
+ /* We can safely assume this is fully in 1:1 mapping & vmemmap area */
+ pte = pte_offset_kernel(pmd, start);
+ for (i = 0; i < PTRS_PER_PTE; i++, pte++)
+ if (!pte_none(*pte))
+ return;
+
+ vmem_pte_free(__va(pmd_deref(*pmd)));
+ pmd_clear(pmd);
+}
+
static void remove_pmd_table(pud_t *pud, unsigned long addr,
unsigned long end, bool direct)
{
@@ -194,12 +218,36 @@ static void remove_pmd_table(pud_t *pud, unsigned long addr,
}
remove_pte_table(pmd, addr, next, direct);
+ try_free_pte_table(pmd, addr & PMD_MASK);
}
if (direct)
update_page_count(PG_DIRECT_MAP_1M, -pages);
}
+static void try_free_pmd_table(pud_t *pud, unsigned long start)
+{
+ const unsigned long end = start + PUD_SIZE;
+ pmd_t *pmd;
+ int i;
+
+ /* Don't mess with any tables not fully in 1:1 mapping & vmemmap area */
+ if (end > VMALLOC_START)
+ return;
+#ifdef CONFIG_KASAN
+ if (start < KASAN_SHADOW_END && KASAN_SHADOW_START > end)
+ return;
+#endif
+
+ pmd = pmd_offset(pud, start);
+ for (i = 0; i < PTRS_PER_PMD; i++, pmd++)
+ if (!pmd_none(*pmd))
+ return;
+
+ vmem_free_pages(pud_deref(*pud), CRST_ALLOC_ORDER);
+ pud_clear(pud);
+}
+
static void remove_pud_table(p4d_t *p4d, unsigned long addr,
unsigned long end, bool direct)
{
@@ -224,12 +272,36 @@ static void remove_pud_table(p4d_t *p4d, unsigned long addr,
}
remove_pmd_table(pud, addr, next, direct);
+ try_free_pmd_table(pud, addr & PUD_MASK);
}
if (direct)
update_page_count(PG_DIRECT_MAP_2G, -pages);
}
+static void try_free_pud_table(p4d_t *p4d, unsigned long start)
+{
+ const unsigned long end = start + P4D_SIZE;
+ pud_t *pud;
+ int i;
+
+ /* Don't mess with any tables not fully in 1:1 mapping & vmemmap area */
+ if (end > VMALLOC_START)
+ return;
+#ifdef CONFIG_KASAN
+ if (start < KASAN_SHADOW_END && KASAN_SHADOW_START > end)
+ return;
+#endif
+
+ pud = pud_offset(p4d, start);
+ for (i = 0; i < PTRS_PER_PUD; i++, pud++)
+ if (!pud_none(*pud))
+ return;
+
+ vmem_free_pages(p4d_deref(*p4d), CRST_ALLOC_ORDER);
+ p4d_clear(p4d);
+}
+
static void remove_p4d_table(pgd_t *pgd, unsigned long addr,
unsigned long end, bool direct)
{
@@ -244,9 +316,33 @@ static void remove_p4d_table(pgd_t *pgd, unsigned long addr,
continue;
remove_pud_table(p4d, addr, next, direct);
+ try_free_pud_table(p4d, addr & P4D_MASK);
}
}
+static void try_free_p4d_table(pgd_t *pgd, unsigned long start)
+{
+ const unsigned long end = start + PGDIR_SIZE;
+ p4d_t *p4d;
+ int i;
+
+ /* Don't mess with any tables not fully in 1:1 mapping & vmemmap area */
+ if (end > VMALLOC_START)
+ return;
+#ifdef CONFIG_KASAN
+ if (start < KASAN_SHADOW_END && KASAN_SHADOW_START > end)
+ return;
+#endif
+
+ p4d = p4d_offset(pgd, start);
+ for (i = 0; i < PTRS_PER_P4D; i++, p4d++)
+ if (!p4d_none(*p4d))
+ return;
+
+ vmem_free_pages(pgd_deref(*pgd), CRST_ALLOC_ORDER);
+ pgd_clear(pgd);
+}
+
static void remove_pagetable(unsigned long start, unsigned long end,
bool direct)
{
@@ -264,6 +360,7 @@ static void remove_pagetable(unsigned long start, unsigned long end,
continue;
remove_p4d_table(pgd, addr, next, direct);
+ try_free_p4d_table(pgd, addr & PGDIR_MASK);
}
flush_tlb_kernel_range(start, end);
@@ -271,7 +368,6 @@ static void remove_pagetable(unsigned long start, unsigned long end,
/*
* Remove a physical memory range from the 1:1 mapping.
- * Currently only invalidates page table entries.
*/
static void vmem_remove_range(unsigned long start, unsigned long size)
{
--
2.26.2
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