Commit 891121e6 authored by Aneesh Kumar K.V's avatar Aneesh Kumar K.V Committed by Michael Ellerman

powerpc/mm: Differentiate between hugetlb and THP during page walk

We need to properly identify whether a hugepage is an explicit or
a transparent hugepage in follow_huge_addr(). We used to depend
on hugepage shift argument to do that. But in some case that can
result in wrong results. For ex:

On finding a transparent hugepage we set hugepage shift to PMD_SHIFT.
But we can end up clearing the thp pte, via pmdp_huge_get_and_clear.
We do prevent reusing the pfn page via the usage of
kick_all_cpus_sync(). But that happens after we updated the pte to 0.
Hence in follow_huge_addr() we can find hugepage shift set, but transparent
huge page check fail for a thp pte.

NOTE: We fixed a variant of this race against thp split in commit
691e95fd
("powerpc/mm/thp: Make page table walk safe against thp split/collapse")

Without this patch, we may hit the BUG_ON(flags & FOLL_GET) in
follow_page_mask occasionally.

In the long term, we may want to switch ppc64 64k page size config to
enable CONFIG_ARCH_WANT_GENERAL_HUGETLB
Reported-by: default avatarDavid Gibson <david@gibson.dropbear.id.au>
Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
parent ec2640b1
......@@ -14,6 +14,7 @@
#include <asm/asm-compat.h>
#include <asm/page.h>
#include <asm/bug.h>
/*
* This is necessary to get the definition of PGTABLE_RANGE which we
......
......@@ -437,9 +437,9 @@ static inline char *get_hpte_slot_array(pmd_t *pmdp)
}
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
extern void hpte_do_hugepage_flush(struct mm_struct *mm, unsigned long addr,
pmd_t *pmdp, unsigned long old_pmd);
#ifdef CONFIG_TRANSPARENT_HUGEPAGE
extern pmd_t pfn_pmd(unsigned long pfn, pgprot_t pgprot);
extern pmd_t mk_pmd(struct page *page, pgprot_t pgprot);
extern pmd_t pmd_modify(pmd_t pmd, pgprot_t newprot);
......@@ -479,6 +479,14 @@ static inline int pmd_trans_splitting(pmd_t pmd)
}
extern int has_transparent_hugepage(void);
#else
static inline void hpte_do_hugepage_flush(struct mm_struct *mm,
unsigned long addr, pmd_t *pmdp,
unsigned long old_pmd)
{
WARN(1, "%s called with THP disabled\n", __func__);
}
#endif /* CONFIG_TRANSPARENT_HUGEPAGE */
static inline int pmd_large(pmd_t pmd)
......
......@@ -259,15 +259,15 @@ extern int gup_hugepte(pte_t *ptep, unsigned long sz, unsigned long addr,
#define has_transparent_hugepage() 0
#endif
pte_t *__find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
unsigned *shift);
bool *is_thp, unsigned *shift);
static inline pte_t *find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
unsigned *shift)
bool *is_thp, unsigned *shift)
{
if (!arch_irqs_disabled()) {
pr_info("%s called with irq enabled\n", __func__);
dump_stack();
}
return __find_linux_pte_or_hugepte(pgdir, ea, shift);
return __find_linux_pte_or_hugepte(pgdir, ea, is_thp, shift);
}
#endif /* __ASSEMBLY__ */
......
......@@ -351,7 +351,8 @@ static inline unsigned long eeh_token_to_phys(unsigned long token)
* worried about _PAGE_SPLITTING/collapse. Also we will not hit
* page table free, because of init_mm.
*/
ptep = __find_linux_pte_or_hugepte(init_mm.pgd, token, &hugepage_shift);
ptep = __find_linux_pte_or_hugepte(init_mm.pgd, token,
NULL, &hugepage_shift);
if (!ptep)
return token;
WARN_ON(hugepage_shift);
......
......@@ -76,7 +76,7 @@ struct iowa_bus *iowa_mem_find_bus(const PCI_IO_ADDR addr)
* a page table free due to init_mm
*/
ptep = __find_linux_pte_or_hugepte(init_mm.pgd, vaddr,
&hugepage_shift);
NULL, &hugepage_shift);
if (ptep == NULL)
paddr = 0;
else {
......
......@@ -543,7 +543,7 @@ int kvmppc_book3s_hv_page_fault(struct kvm_run *run, struct kvm_vcpu *vcpu,
*/
local_irq_save(flags);
ptep = find_linux_pte_or_hugepte(current->mm->pgd,
hva, NULL);
hva, NULL, NULL);
if (ptep) {
pte = kvmppc_read_update_linux_pte(ptep, 1);
if (pte_write(pte))
......
......@@ -32,7 +32,7 @@ static void *real_vmalloc_addr(void *x)
* So don't worry about THP collapse/split. Called
* Only in realmode, hence won't need irq_save/restore.
*/
p = __find_linux_pte_or_hugepte(swapper_pg_dir, addr, NULL);
p = __find_linux_pte_or_hugepte(swapper_pg_dir, addr, NULL, NULL);
if (!p || !pte_present(*p))
return NULL;
addr = (pte_pfn(*p) << PAGE_SHIFT) | (addr & ~PAGE_MASK);
......@@ -221,10 +221,12 @@ long kvmppc_do_h_enter(struct kvm *kvm, unsigned long flags,
* retry via mmu_notifier_retry.
*/
if (realmode)
ptep = __find_linux_pte_or_hugepte(pgdir, hva, &hpage_shift);
ptep = __find_linux_pte_or_hugepte(pgdir, hva, NULL,
&hpage_shift);
else {
local_irq_save(irq_flags);
ptep = find_linux_pte_or_hugepte(pgdir, hva, &hpage_shift);
ptep = find_linux_pte_or_hugepte(pgdir, hva, NULL,
&hpage_shift);
}
if (ptep) {
pte_t pte;
......
......@@ -476,7 +476,7 @@ static inline int kvmppc_e500_shadow_map(struct kvmppc_vcpu_e500 *vcpu_e500,
* can't run hence pfn won't change.
*/
local_irq_save(flags);
ptep = find_linux_pte_or_hugepte(pgdir, hva, NULL);
ptep = find_linux_pte_or_hugepte(pgdir, hva, NULL, NULL);
if (ptep) {
pte_t pte = READ_ONCE(*ptep);
......
......@@ -994,6 +994,7 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea,
unsigned long access, unsigned long trap,
unsigned long flags)
{
bool is_thp;
enum ctx_state prev_state = exception_enter();
pgd_t *pgdir;
unsigned long vsid;
......@@ -1068,7 +1069,7 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea,
#endif /* CONFIG_PPC_64K_PAGES */
/* Get PTE and page size from page tables */
ptep = __find_linux_pte_or_hugepte(pgdir, ea, &hugeshift);
ptep = __find_linux_pte_or_hugepte(pgdir, ea, &is_thp, &hugeshift);
if (ptep == NULL || !pte_present(*ptep)) {
DBG_LOW(" no PTE !\n");
rc = 1;
......@@ -1088,7 +1089,7 @@ int hash_page_mm(struct mm_struct *mm, unsigned long ea,
}
if (hugeshift) {
if (pmd_trans_huge(*(pmd_t *)ptep))
if (is_thp)
rc = __hash_page_thp(ea, access, vsid, (pmd_t *)ptep,
trap, flags, ssize, psize);
#ifdef CONFIG_HUGETLB_PAGE
......@@ -1243,7 +1244,7 @@ void hash_preload(struct mm_struct *mm, unsigned long ea,
* THP pages use update_mmu_cache_pmd. We don't do
* hash preload there. Hence can ignore THP here
*/
ptep = find_linux_pte_or_hugepte(pgdir, ea, &hugepage_shift);
ptep = find_linux_pte_or_hugepte(pgdir, ea, NULL, &hugepage_shift);
if (!ptep)
goto out_exit;
......
......@@ -128,7 +128,7 @@ int pgd_huge(pgd_t pgd)
pte_t *huge_pte_offset(struct mm_struct *mm, unsigned long addr)
{
/* Only called for hugetlbfs pages, hence can ignore THP */
return __find_linux_pte_or_hugepte(mm->pgd, addr, NULL);
return __find_linux_pte_or_hugepte(mm->pgd, addr, NULL, NULL);
}
static int __hugepte_alloc(struct mm_struct *mm, hugepd_t *hpdp,
......@@ -703,13 +703,14 @@ void hugetlb_free_pgd_range(struct mmu_gather *tlb,
struct page *
follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
{
bool is_thp;
pte_t *ptep, pte;
unsigned shift;
unsigned long mask, flags;
struct page *page = ERR_PTR(-EINVAL);
local_irq_save(flags);
ptep = find_linux_pte_or_hugepte(mm->pgd, address, &shift);
ptep = find_linux_pte_or_hugepte(mm->pgd, address, &is_thp, &shift);
if (!ptep)
goto no_page;
pte = READ_ONCE(*ptep);
......@@ -718,7 +719,7 @@ follow_huge_addr(struct mm_struct *mm, unsigned long address, int write)
* Transparent hugepages are handled by generic code. We can skip them
* here.
*/
if (!shift || pmd_trans_huge(__pmd(pte_val(pte))))
if (!shift || is_thp)
goto no_page;
if (!pte_present(pte)) {
......@@ -975,7 +976,7 @@ void flush_dcache_icache_hugepage(struct page *page)
*/
pte_t *__find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
unsigned *shift)
bool *is_thp, unsigned *shift)
{
pgd_t pgd, *pgdp;
pud_t pud, *pudp;
......@@ -987,6 +988,9 @@ pte_t *__find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
if (shift)
*shift = 0;
if (is_thp)
*is_thp = false;
pgdp = pgdir + pgd_index(ea);
pgd = READ_ONCE(*pgdp);
/*
......@@ -1034,7 +1038,14 @@ pte_t *__find_linux_pte_or_hugepte(pgd_t *pgdir, unsigned long ea,
if (pmd_none(pmd))
return NULL;
if (pmd_huge(pmd) || pmd_large(pmd)) {
if (pmd_trans_huge(pmd)) {
if (is_thp)
*is_thp = true;
ret_pte = (pte_t *) pmdp;
goto out;
}
if (pmd_huge(pmd)) {
ret_pte = (pte_t *) pmdp;
goto out;
} else if (is_hugepd(__hugepd(pmd_val(pmd))))
......
......@@ -190,6 +190,7 @@ void tlb_flush(struct mmu_gather *tlb)
void __flush_hash_table_range(struct mm_struct *mm, unsigned long start,
unsigned long end)
{
bool is_thp;
int hugepage_shift;
unsigned long flags;
......@@ -208,21 +209,21 @@ void __flush_hash_table_range(struct mm_struct *mm, unsigned long start,
local_irq_save(flags);
arch_enter_lazy_mmu_mode();
for (; start < end; start += PAGE_SIZE) {
pte_t *ptep = find_linux_pte_or_hugepte(mm->pgd, start,
pte_t *ptep = find_linux_pte_or_hugepte(mm->pgd, start, &is_thp,
&hugepage_shift);
unsigned long pte;
if (ptep == NULL)
continue;
pte = pte_val(*ptep);
if (hugepage_shift)
if (is_thp)
trace_hugepage_invalidate(start, pte);
if (!(pte & _PAGE_HASHPTE))
continue;
if (unlikely(hugepage_shift && pmd_trans_huge(*(pmd_t *)pte)))
if (unlikely(is_thp))
hpte_do_hugepage_flush(mm, start, (pmd_t *)ptep, pte);
else
hpte_need_flush(mm, start, ptep, pte, 0);
hpte_need_flush(mm, start, ptep, pte, hugepage_shift);
}
arch_leave_lazy_mmu_mode();
local_irq_restore(flags);
......
......@@ -127,7 +127,7 @@ static int read_user_stack_slow(void __user *ptr, void *buf, int nb)
return -EFAULT;
local_irq_save(flags);
ptep = find_linux_pte_or_hugepte(pgdir, addr, &shift);
ptep = find_linux_pte_or_hugepte(pgdir, addr, NULL, &shift);
if (!ptep)
goto err_out;
if (!shift)
......
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