powerpc: rework FSL Book-E PTE access and TLB miss

This converts the FSL Book-E PTE access and TLB miss handling to match
with the recent changes to 44x that introduce support for non-atomic PTE
operations in pgtable-ppc32.h and removes write back to the PTE from
the TLB miss handlers. In addition, the DSI interrupt code no longer
tries to fixup write permission, this is left to generic code, and
_PAGE_HWWRITE is gone.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>

1 files changed, 44 insertions, 124 deletions

diff --git a/arch/powerpc/kernel/head_fsl_booke.S b/arch/powerpc/kernel/head_fsl_booke.S
index c4268500e856..7d554968b635 100644
--- a/arch/powerpc/kernel/head_fsl_booke.S
+++ b/arch/powerpc/kernel/head_fsl_booke.S
@@ -483,90 +483,16 @@ interrupt_base:
 
         /* Data Storage Interrupt */
         START_EXCEPTION(DataStorage)
-        mtspr   SPRN_SPRG0, r10         /* Save some working registers */
-        mtspr   SPRN_SPRG1, r11
-        mtspr   SPRN_SPRG4W, r12
-        mtspr   SPRN_SPRG5W, r13
-        mfcr    r11
-        mtspr   SPRN_SPRG7W, r11
-
-        /*
-         * Check if it was a store fault, if not then bail
-         * because a user tried to access a kernel or
-         * read-protected page.  Otherwise, get the
-         * offending address and handle it.
-         */
-        mfspr   r10, SPRN_ESR
-        andis.  r10, r10, ESR_ST@h
-        beq     2f
-
-        mfspr   r10, SPRN_DEAR          /* Get faulting address */
-
-        /* If we are faulting a kernel address, we have to use the
-         * kernel page tables.
-         */
-        lis     r11, PAGE_OFFSET@h
-        cmplw   0, r10, r11
-        bge     2f
-
-        /* Get the PGD for the current thread */
-3:
-        mfspr   r11,SPRN_SPRG3
-        lwz     r11,PGDIR(r11)
-4:
-        FIND_PTE
-
-        /* Are _PAGE_USER & _PAGE_RW set & _PAGE_HWWRITE not? */
-        andi.   r13, r11, _PAGE_RW|_PAGE_USER|_PAGE_HWWRITE
-        cmpwi   0, r13, _PAGE_RW|_PAGE_USER
-        bne     2f                      /* Bail if not */
-
-        /* Update 'changed'. */
-        ori     r11, r11, _PAGE_DIRTY|_PAGE_ACCESSED|_PAGE_HWWRITE
-        stw     r11, PTE_FLAGS_OFFSET(r12) /* Update Linux page table */
-
-        /* MAS2 not updated as the entry does exist in the tlb, this
-           fault taken to detect state transition (eg: COW -> DIRTY)
-         */
-        andi.   r11, r11, _PAGE_HWEXEC
-        rlwimi  r11, r11, 31, 27, 27    /* SX <- _PAGE_HWEXEC */
-        ori     r11, r11, (MAS3_UW|MAS3_SW|MAS3_UR|MAS3_SR)@l /* set static perms */
-
-        /* update search PID in MAS6, AS = 0 */
-        mfspr   r12, SPRN_PID0
-        slwi    r12, r12, 16
-        mtspr   SPRN_MAS6, r12
-
-        /* find the TLB index that caused the fault.  It has to be here. */
-        tlbsx   0, r10
-
-        /* only update the perm bits, assume the RPN is fine */
-        mfspr   r12, SPRN_MAS3
-        rlwimi  r12, r11, 0, 20, 31
-        mtspr   SPRN_MAS3,r12
-        tlbwe
-
-        /* Done...restore registers and get out of here.  */
-        mfspr   r11, SPRN_SPRG7R
-        mtcr    r11
-        mfspr   r13, SPRN_SPRG5R
-        mfspr   r12, SPRN_SPRG4R
-        mfspr   r11, SPRN_SPRG1
-        mfspr   r10, SPRN_SPRG0
-        rfi                     /* Force context change */
-
-2:
-        /*
-         * The bailout.  Restore registers to pre-exception conditions
-         * and call the heavyweights to help us out.
-         */
-        mfspr   r11, SPRN_SPRG7R
-        mtcr    r11
-        mfspr   r13, SPRN_SPRG5R
-        mfspr   r12, SPRN_SPRG4R
-        mfspr   r11, SPRN_SPRG1
-        mfspr   r10, SPRN_SPRG0
-        b       data_access
+        NORMAL_EXCEPTION_PROLOG
+        mfspr   r5,SPRN_ESR             /* Grab the ESR, save it, pass arg3 */
+        stw     r5,_ESR(r11)
+        mfspr   r4,SPRN_DEAR            /* Grab the DEAR, save it, pass arg2 */
+        andis.  r10,r5,(ESR_ILK|ESR_DLK)@h
+        bne     1f
+        EXC_XFER_EE_LITE(0x0300, handle_page_fault)
+1:
+        addi    r3,r1,STACK_FRAME_OVERHEAD
+        EXC_XFER_EE_LITE(0x0300, CacheLockingException)
 
         /* Instruction Storage Interrupt */
         INSTRUCTION_STORAGE_EXCEPTION
@@ -645,15 +571,30 @@ interrupt_base:
         lwz     r11,PGDIR(r11)
 
 4:
+        /* Mask of required permission bits. Note that while we
+         * do copy ESR:ST to _PAGE_RW position as trying to write
+         * to an RO page is pretty common, we don't do it with
+         * _PAGE_DIRTY. We could do it, but it's a fairly rare
+         * event so I'd rather take the overhead when it happens
+         * rather than adding an instruction here. We should measure
+         * whether the whole thing is worth it in the first place
+         * as we could avoid loading SPRN_ESR completely in the first
+         * place...
+         *
+         * TODO: Is it worth doing that mfspr & rlwimi in the first
+         *       place or can we save a couple of instructions here ?
+         */
+        mfspr   r12,SPRN_ESR
+        li      r13,_PAGE_PRESENT|_PAGE_ACCESSED
+        rlwimi  r13,r12,11,29,29
+
         FIND_PTE
-        andi.   r13, r11, _PAGE_PRESENT /* Is the page present? */
-        beq     2f                      /* Bail if not present */
+        andc.   r13,r13,r11             /* Check permission */
+        bne     2f                      /* Bail if permission mismach */
 
 #ifdef CONFIG_PTE_64BIT
         lwz     r13, 0(r12)
 #endif
-        ori     r11, r11, _PAGE_ACCESSED
-        stw     r11, PTE_FLAGS_OFFSET(r12)
 
          /* Jump to common tlb load */
         b       finish_tlb_load
@@ -667,7 +608,7 @@ interrupt_base:
         mfspr   r12, SPRN_SPRG4R
         mfspr   r11, SPRN_SPRG1
         mfspr   r10, SPRN_SPRG0
-        b       data_access
+        b       DataStorage
 
         /* Instruction TLB Error Interrupt */
         /*
@@ -705,15 +646,16 @@ interrupt_base:
         lwz     r11,PGDIR(r11)
 
 4:
+        /* Make up the required permissions */
+        li      r13,_PAGE_PRESENT | _PAGE_ACCESSED | _PAGE_HWEXEC
+
         FIND_PTE
-        andi.   r13, r11, _PAGE_PRESENT /* Is the page present? */
-        beq     2f                      /* Bail if not present */
+        andc.   r13,r13,r11             /* Check permission */
+        bne     2f                      /* Bail if permission mismach */
 
 #ifdef CONFIG_PTE_64BIT
         lwz     r13, 0(r12)
 #endif
-        ori     r11, r11, _PAGE_ACCESSED
-        stw     r11, PTE_FLAGS_OFFSET(r12)
 
         /* Jump to common TLB load point */
         b       finish_tlb_load
@@ -768,29 +710,13 @@ interrupt_base:
  * Local functions
  */
 
-        /*
-         * Data TLB exceptions will bail out to this point
-         * if they can't resolve the lightweight TLB fault.
-         */
-data_access:
-        NORMAL_EXCEPTION_PROLOG
-        mfspr   r5,SPRN_ESR             /* Grab the ESR, save it, pass arg3 */
-        stw     r5,_ESR(r11)
-        mfspr   r4,SPRN_DEAR            /* Grab the DEAR, save it, pass arg2 */
-        andis.  r10,r5,(ESR_ILK|ESR_DLK)@h
-        bne     1f
-        EXC_XFER_EE_LITE(0x0300, handle_page_fault)
-1:
-        addi    r3,r1,STACK_FRAME_OVERHEAD
-        EXC_XFER_EE_LITE(0x0300, CacheLockingException)
-
 /*
-
  * Both the instruction and data TLB miss get to this
  * point to load the TLB.
  *      r10 - EA of fault
  *      r11 - TLB (info from Linux PTE)
- *      r12, r13 - available to use
+ *      r12 - available to use
+ *      r13 - upper bits of PTE (if PTE_64BIT) or available to use
  *      CR5 - results of addr >= PAGE_OFFSET
  *      MAS0, MAS1 - loaded with proper value when we get here
  *      MAS2, MAS3 - will need additional info from Linux PTE
@@ -812,20 +738,14 @@ finish_tlb_load:
 #endif
         mtspr   SPRN_MAS2, r12
 
-        bge     5, 1f
-
-        /* is user addr */
-        andi.   r12, r11, (_PAGE_USER | _PAGE_HWWRITE | _PAGE_HWEXEC)
+        li      r10, (_PAGE_HWEXEC | _PAGE_PRESENT)
+        rlwimi  r10, r11, 31, 29, 29    /* extract _PAGE_DIRTY into SW */
+        and     r12, r11, r10
         andi.   r10, r11, _PAGE_USER    /* Test for _PAGE_USER */
-        srwi    r10, r12, 1
-        or      r12, r12, r10   /* Copy user perms into supervisor */
-        iseleq  r12, 0, r12
-        b       2f
-
-        /* is kernel addr */
-1:      rlwinm  r12, r11, 31, 29, 29    /* Extract _PAGE_HWWRITE into SW */
-        ori     r12, r12, (MAS3_SX | MAS3_SR)
-
+        slwi    r10, r12, 1
+        or      r10, r10, r12
+        iseleq  r12, r12, r10
+        
 #ifdef CONFIG_PTE_64BIT
 2:      rlwimi  r12, r13, 24, 0, 7      /* grab RPN[32:39] */
         rlwimi  r12, r11, 24, 8, 19     /* grab RPN[40:51] */