powerpc/40x: Rework 40x PTE access and TLB miss

Commit 1bc54c03117b ("powerpc: rework 4xx PTE access and TLB miss")
reworked 44x PTE access to avoid atomic pte updates, and
left 8xx, 40x and fsl booke with atomic pte updates.
Commit 6cfd8990e27d ("powerpc: rework FSL Book-E PTE access and TLB
miss") removed atomic pte updates on fsl booke.
It went away on 8xx with commit ddfc20a3b9ae ("powerpc/8xx: Remove
PTE_ATOMIC_UPDATES").

40x is the last platform setting PTE_ATOMIC_UPDATES.

Rework PTE access and TLB miss to remove PTE_ATOMIC_UPDATES for 40x:
- Always handle DSI as a fault.
- Bail out of TLB miss handler when CONFIG_SWAP is set and
_PAGE_ACCESSED is not set.
- Bail out of ITLB miss handler when _PAGE_EXEC is not set.
- Only set WR bit when both _PAGE_RW and _PAGE_DIRTY are set.
- Remove _PAGE_HWWRITE
- Don't require PTE_ATOMIC_UPDATES anymore

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/99a0fcd337ef67088140d1647d75fea026a70413.1590079968.git.christophe.leroy@csgroup.eu

2 files changed, 3 insertions, 22 deletions

diff --git a/arch/powerpc/include/asm/nohash/32/pte-40x.h b/arch/powerpc/include/asm/nohash/32/pte-40x.h
index 12c6811e344b..2d3153cfc0d7 100644
--- a/arch/powerpc/include/asm/nohash/32/pte-40x.h
+++ b/arch/powerpc/include/asm/nohash/32/pte-40x.h
@@ -44,9 +44,8 @@
 #define	_PAGE_WRITETHRU	0x008	/* W: caching is write-through */
 #define	_PAGE_USER	0x010	/* matches one of the zone permission bits */
 #define	_PAGE_SPECIAL	0x020	/* software: Special page */
-#define	_PAGE_RW	0x040	/* software: Writes permitted */
 #define	_PAGE_DIRTY	0x080	/* software: dirty page */
-#define _PAGE_HWWRITE	0x100	/* hardware: Dirty & RW, set in exception */
+#define _PAGE_RW	0x100	/* hardware: WR, anded with dirty in exception */
 #define _PAGE_EXEC	0x200	/* hardware: EX permission */
 #define _PAGE_ACCESSED	0x400	/* software: R: page referenced */
 
@@ -58,8 +57,8 @@
 
 #define _PAGE_KERNEL_RO		0
 #define _PAGE_KERNEL_ROX	_PAGE_EXEC
-#define _PAGE_KERNEL_RW		(_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE)
-#define _PAGE_KERNEL_RWX	(_PAGE_DIRTY | _PAGE_RW | _PAGE_HWWRITE | _PAGE_EXEC)
+#define _PAGE_KERNEL_RW		(_PAGE_DIRTY | _PAGE_RW)
+#define _PAGE_KERNEL_RWX	(_PAGE_DIRTY | _PAGE_RW | _PAGE_EXEC)
 
 #define _PMD_PRESENT	0x400	/* PMD points to page of PTEs */
 #define _PMD_PRESENT_MASK	_PMD_PRESENT
@@ -85,21 +84,5 @@
 #define PAGE_READONLY	__pgprot(_PAGE_BASE | _PAGE_USER)
 #define PAGE_READONLY_X	__pgprot(_PAGE_BASE | _PAGE_USER | _PAGE_EXEC)
 
-#ifndef __ASSEMBLY__
-static inline pte_t pte_wrprotect(pte_t pte)
-{
-	return __pte(pte_val(pte) & ~(_PAGE_RW | _PAGE_HWWRITE));
-}
-
-#define pte_wrprotect pte_wrprotect
-
-static inline pte_t pte_mkclean(pte_t pte)
-{
-	return __pte(pte_val(pte) & ~(_PAGE_DIRTY | _PAGE_HWWRITE));
-}
-
-#define pte_mkclean pte_mkclean
-#endif
-
 #endif /* __KERNEL__ */
 #endif /*  _ASM_POWERPC_NOHASH_32_PTE_40x_H */
diff --git a/arch/powerpc/include/asm/nohash/pgtable.h b/arch/powerpc/include/asm/nohash/pgtable.h
index f27c967d9269..50a4b0bb8d16 100644
--- a/arch/powerpc/include/asm/nohash/pgtable.h
+++ b/arch/powerpc/include/asm/nohash/pgtable.h
@@ -130,12 +130,10 @@ static inline pte_t pte_exprotect(pte_t pte)
 	return __pte(pte_val(pte) & ~_PAGE_EXEC);
 }
 
-#ifndef pte_mkclean
 static inline pte_t pte_mkclean(pte_t pte)
 {
 	return __pte(pte_val(pte) & ~_PAGE_DIRTY);
 }
-#endif
 
 static inline pte_t pte_mkold(pte_t pte)
 {