From: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com
commit 36b78402d97a3b9aeab136feb9b00d8647ec2c20 upstream.
H_PAGE_THP_HUGE is used to differentiate between a THP hugepage and hugetlb hugepage entries. The difference is WRT how we handle hash fault on these address. THP address enables MPSS in segments. We want to manage devmap hugepage entries similar to THP pt entries. Hence use H_PAGE_THP_HUGE for devmap huge PTE entries.
With current code while handling hash PTE fault, we do set is_thp = true when finding devmap PTE huge PTE entries.
Current code also does the below sequence we setting up huge devmap entries.
entry = pmd_mkhuge(pfn_t_pmd(pfn, prot)); if (pfn_t_devmap(pfn)) entry = pmd_mkdevmap(entry);
In that case we would find both H_PAGE_THP_HUGE and PAGE_DEVMAP set for huge devmap PTE entries. This results in false positive error like below.
kernel BUG at /home/kvaneesh/src/linux/mm/memory.c:4321! Oops: Exception in kernel mode, sig: 5 [#1] LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries Modules linked in: CPU: 56 PID: 67996 Comm: t_mmap_dio Not tainted 5.6.0-rc4-59640-g371c804dedbc #128 .... NIP [c00000000044c9e4] __follow_pte_pmd+0x264/0x900 LR [c0000000005d45f8] dax_writeback_one+0x1a8/0x740 Call Trace: str_spec.74809+0x22ffb4/0x2d116c (unreliable) dax_writeback_one+0x1a8/0x740 dax_writeback_mapping_range+0x26c/0x700 ext4_dax_writepages+0x150/0x5a0 do_writepages+0x68/0x180 __filemap_fdatawrite_range+0x138/0x180 file_write_and_wait_range+0xa4/0x110 ext4_sync_file+0x370/0x6e0 vfs_fsync_range+0x70/0xf0 sys_msync+0x220/0x2e0 system_call+0x5c/0x68
This is because our pmd_trans_huge check doesn't exclude _PAGE_DEVMAP.
To make this all consistent, update pmd_mkdevmap to set H_PAGE_THP_HUGE and pmd_trans_huge check now excludes _PAGE_DEVMAP correctly.
Fixes: ebd31197931d ("powerpc/mm: Add devmap support for ppc64") Cc: stable@vger.kernel.org # v4.13+ Signed-off-by: Aneesh Kumar K.V aneesh.kumar@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://lore.kernel.org/r/20200313094842.351830-1-aneesh.kumar@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/powerpc/include/asm/book3s/64/hash-4k.h | 6 ++++++ arch/powerpc/include/asm/book3s/64/hash-64k.h | 8 +++++++- arch/powerpc/include/asm/book3s/64/pgtable.h | 4 +++- arch/powerpc/include/asm/book3s/64/radix.h | 5 +++++ 4 files changed, 21 insertions(+), 2 deletions(-)
--- a/arch/powerpc/include/asm/book3s/64/hash-4k.h +++ b/arch/powerpc/include/asm/book3s/64/hash-4k.h @@ -108,6 +108,12 @@ extern pmd_t hash__pmdp_huge_get_and_cle extern int hash__has_transparent_hugepage(void); #endif
+static inline pmd_t hash__pmd_mkdevmap(pmd_t pmd) +{ + BUG(); + return pmd; +} + #endif /* !__ASSEMBLY__ */
#endif /* _ASM_POWERPC_BOOK3S_64_HASH_4K_H */ --- a/arch/powerpc/include/asm/book3s/64/hash-64k.h +++ b/arch/powerpc/include/asm/book3s/64/hash-64k.h @@ -181,7 +181,7 @@ static inline void mark_hpte_slot_valid( */ static inline int hash__pmd_trans_huge(pmd_t pmd) { - return !!((pmd_val(pmd) & (_PAGE_PTE | H_PAGE_THP_HUGE)) == + return !!((pmd_val(pmd) & (_PAGE_PTE | H_PAGE_THP_HUGE | _PAGE_DEVMAP)) == (_PAGE_PTE | H_PAGE_THP_HUGE)); }
@@ -209,6 +209,12 @@ extern pmd_t hash__pmdp_huge_get_and_cle unsigned long addr, pmd_t *pmdp); extern int hash__has_transparent_hugepage(void); #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ + +static inline pmd_t hash__pmd_mkdevmap(pmd_t pmd) +{ + return __pmd(pmd_val(pmd) | (_PAGE_PTE | H_PAGE_THP_HUGE | _PAGE_DEVMAP)); +} + #endif /* __ASSEMBLY__ */
#endif /* _ASM_POWERPC_BOOK3S_64_HASH_64K_H */ --- a/arch/powerpc/include/asm/book3s/64/pgtable.h +++ b/arch/powerpc/include/asm/book3s/64/pgtable.h @@ -1179,7 +1179,9 @@ extern void serialize_against_pte_lookup
static inline pmd_t pmd_mkdevmap(pmd_t pmd) { - return __pmd(pmd_val(pmd) | (_PAGE_PTE | _PAGE_DEVMAP)); + if (radix_enabled()) + return radix__pmd_mkdevmap(pmd); + return hash__pmd_mkdevmap(pmd); }
static inline int pmd_devmap(pmd_t pmd) --- a/arch/powerpc/include/asm/book3s/64/radix.h +++ b/arch/powerpc/include/asm/book3s/64/radix.h @@ -289,6 +289,11 @@ extern pmd_t radix__pmdp_huge_get_and_cl extern int radix__has_transparent_hugepage(void); #endif
+static inline pmd_t radix__pmd_mkdevmap(pmd_t pmd) +{ + return __pmd(pmd_val(pmd) | (_PAGE_PTE | _PAGE_DEVMAP)); +} + extern int __meminit radix__vmemmap_create_mapping(unsigned long start, unsigned long page_size, unsigned long phys);