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s390/vmem: cleanup empty page tables

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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: Vasily Gorbik <gor@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@de.ibm.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Message-Id: <20200722094558.9828-7-david@redhat.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
This commit is contained in:
David Hildenbrand 2020-07-22 11:45:55 +02:00 committed by Heiko Carstens
parent aa18e0e658
commit b9ff81003c
1 changed files with 101 additions and 1 deletions
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102
arch/s390/mm/vmem.c
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@ -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);
}
/* __ref: we'll only call vmemmap_alloc_block() via vmemmap_populate() */
static int __ref modify_pte_table(pmd_t *pmd, unsigned long addr,
unsigned long end, bool add, bool direct)
@ -105,6 +114,21 @@ static int __ref modify_pte_table(pmd_t *pmd, unsigned long addr,
return ret;
}
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);
}
/* __ref: we'll only call vmemmap_alloc_block() via vmemmap_populate() */
static int __ref modify_pmd_table(pud_t *pud, unsigned long addr,
unsigned long end, bool add, bool direct)
@ -171,6 +195,8 @@ static int __ref modify_pmd_table(pud_t *pud, unsigned long addr,
ret = modify_pte_table(pmd, addr, next, add, direct);
if (ret)
goto out;
if (!add)
try_free_pte_table(pmd, addr & PMD_MASK);
}
ret = 0;
out:
@ -179,6 +205,29 @@ static int __ref modify_pmd_table(pud_t *pud, unsigned long addr,
return ret;
}
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 int modify_pud_table(p4d_t *p4d, unsigned long addr, unsigned long end,
bool add, bool direct)
{
@ -225,6 +274,8 @@ static int modify_pud_table(p4d_t *p4d, unsigned long addr, unsigned long end,
ret = modify_pmd_table(pud, addr, next, add, direct);
if (ret)
goto out;
if (!add)
try_free_pmd_table(pud, addr & PUD_MASK);
}
ret = 0;
out:
@ -233,6 +284,29 @@ static int modify_pud_table(p4d_t *p4d, unsigned long addr, unsigned long end,
return ret;
}
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 int modify_p4d_table(pgd_t *pgd, unsigned long addr, unsigned long end,
bool add, bool direct)
{
@ -257,12 +331,37 @@ static int modify_p4d_table(pgd_t *pgd, unsigned long addr, unsigned long end,
ret = modify_pud_table(p4d, addr, next, add, direct);
if (ret)
goto out;
if (!add)
try_free_pud_table(p4d, addr & P4D_MASK);
}
ret = 0;
out:
return ret;
}
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 int modify_pagetable(unsigned long start, unsigned long end, bool add,
bool direct)
{
@ -291,6 +390,8 @@ static int modify_pagetable(unsigned long start, unsigned long end, bool add,
ret = modify_p4d_table(pgd, addr, next, add, direct);
if (ret)
goto out;
if (!add)
try_free_p4d_table(pgd, addr & PGDIR_MASK);
}
ret = 0;
out:
@ -319,7 +420,6 @@ static int vmem_add_range(unsigned long start, unsigned long size)
/*
* 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)
{