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Commit fe11dc3f authored by Joakim Tjernlund's avatar Joakim Tjernlund Committed by Benjamin Herrenschmidt
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powerpc/8xx: Update TLB asm so it behaves as linux mm expects. 



Update the TLB asm to make proper use of _PAGE_DIRY and _PAGE_ACCESSED.
Get rid of _PAGE_HWWRITE too.
Pros:
 - I/D TLB Miss never needs to write to the linux pte.
 - _PAGE_ACCESSED is only set on TLB Error fixing accounting
 - _PAGE_DIRTY is mapped to 0x100, the changed bit, and is set directly
    when a page has been made dirty.
 - Proper RO/RW mapping of user space.
 - Free up 2 SW TLB bits in the linux pte(add back _PAGE_WRITETHRU ?)
 - kernel RO/user NA support.
Cons:
 - A few more instructions in the TLB Miss routines.

Signed-off-by: default avatarJoakim Tjernlund <Joakim.Tjernlund@transmode.se>
Signed-off-by: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 5efab4a0

arch/powerpc/include/asm/pte-8xx.h

+6 −7
Original line number Diff line number Diff line
@@ -33,21 +33,20 @@ 
#define _PAGE_NO_CACHE	0x0002	/* I: cache inhibit */

#define _PAGE_SHARED	0x0004	/* No ASID (context) compare */

#define _PAGE_SPECIAL	0x0008	/* SW entry, forced to 0 by the TLB miss */

#define _PAGE_DIRTY	0x0100	/* C: page changed */



/* These five software bits must be masked out when the entry is loaded

 * into the TLB.

/* These 3 software bits must be masked out when the entry is loaded

 * into the TLB, 2 SW bits left.

 */

#define _PAGE_GUARDED	0x0010	/* software: guarded access */

#define _PAGE_DIRTY	0x0020	/* software: page changed */

#define _PAGE_RW	0x0040	/* software: user write access allowed */

#define _PAGE_ACCESSED	0x0080	/* software: page referenced */

#define _PAGE_ACCESSED	0x0020	/* software: page referenced */



/* Setting any bits in the nibble with the follow two controls will

 * require a TLB exception handler change.  It is assumed unused bits

 * are always zero.

 */

#define _PAGE_HWWRITE	0x0100	/* h/w write enable: never set in Linux PTE */

#define _PAGE_USER	0x0800	/* One of the PP bits, the other is USER&~RW */

#define _PAGE_RW	0x0400	/* lsb PP bits, inverted in HW */

#define _PAGE_USER	0x0800	/* msb PP bits */



#define _PMD_PRESENT	0x0001

#define _PMD_BAD	0x0ff0

arch/powerpc/kernel/head_8xx.S

+51 −48
Original line number Diff line number Diff line
@@ -333,26 +333,20 @@ InstructionTLBMiss: 
	mfspr	r11, SPRN_MD_TWC	/* ....and get the pte address */

	lwz	r10, 0(r11)	/* Get the pte */



#ifdef CONFIG_SWAP

	/* do not set the _PAGE_ACCESSED bit of a non-present page */

	andi.	r11, r10, _PAGE_PRESENT

	beq	4f

	ori	r10, r10, _PAGE_ACCESSED

	mfspr	r11, SPRN_MD_TWC	/* get the pte address again */

	stw	r10, 0(r11)

4:

#else

	ori	r10, r10, _PAGE_ACCESSED

	stw	r10, 0(r11)

#endif

	andi.	r11, r10, _PAGE_ACCESSED | _PAGE_PRESENT

	cmpwi	cr0, r11, _PAGE_ACCESSED | _PAGE_PRESENT

	bne-	cr0, 2f



	/* Clear PP lsb, 0x400 */

	rlwinm 	r10, r10, 0, 22, 20



	/* The Linux PTE won't go exactly into the MMU TLB.

	 * Software indicator bits 21, 22 and 28 must be clear.

	 * Software indicator bits 22 and 28 must be clear.

	 * Software indicator bits 24, 25, 26, and 27 must be

	 * set.  All other Linux PTE bits control the behavior

	 * of the MMU.

	 */

2:	li	r11, 0x00f0

	li	r11, 0x00f0

	rlwimi	r10, r11, 0, 24, 28	/* Set 24-27, clear 28 */

	DO_8xx_CPU6(0x2d80, r3)

	mtspr	SPRN_MI_RPN, r10	/* Update TLB entry */
@@ -365,6 +359,22 @@ InstructionTLBMiss: 
	lwz	r3, 8(r0)

#endif

	rfi

2:

	mfspr	r11, SPRN_SRR1

	/* clear all error bits as TLB Miss

	 * sets a few unconditionally

	*/

	rlwinm	r11, r11, 0, 0xffff

	mtspr	SPRN_SRR1, r11



	mfspr	r10, SPRN_M_TW	/* Restore registers */

	lwz	r11, 0(r0)

	mtcr	r11

	lwz	r11, 4(r0)

#ifdef CONFIG_8xx_CPU6

	lwz	r3, 8(r0)

#endif

	b	InstructionAccess



	. = 0x1200

DataStoreTLBMiss:
@@ -409,21 +419,27 @@ DataStoreTLBMiss: 
	DO_8xx_CPU6(0x3b80, r3)

	mtspr	SPRN_MD_TWC, r11



#ifdef CONFIG_SWAP

	/* do not set the _PAGE_ACCESSED bit of a non-present page */

	andi.	r11, r10, _PAGE_PRESENT

	beq	4f

	ori	r10, r10, _PAGE_ACCESSED

4:

	/* and update pte in table */

#else

	ori	r10, r10, _PAGE_ACCESSED

#endif

	mfspr	r11, SPRN_MD_TWC	/* get the pte address again */

	stw	r10, 0(r11)

	/* Both _PAGE_ACCESSED and _PAGE_PRESENT has to be set.

	 * We also need to know if the insn is a load/store, so:

	 * Clear _PAGE_PRESENT and load that which will

	 * trap into DTLB Error with store bit set accordinly.

	 */

	/* PRESENT=0x1, ACCESSED=0x20

	 * r11 = ((r10 & PRESENT) & ((r10 & ACCESSED) >> 5));

	 * r10 = (r10 & ~PRESENT) | r11;

	 */

	rlwinm	r11, r10, 32-5, 31, 31

	and	r11, r11, r10

	rlwimi	r10, r11, 0, 31, 31



	/* Honour kernel RO, User NA */

	andi.	r11, r10, _PAGE_USER | _PAGE_RW

	bne-	cr0, 5f

	ori	r10,r10, 0x200 /* Extended encoding, bit 22 */

5:	xori	r10, r10, _PAGE_RW  /* invert RW bit */



	/* The Linux PTE won't go exactly into the MMU TLB.

	 * Software indicator bits 21, 22 and 28 must be clear.

	 * Software indicator bits 22 and 28 must be clear.

	 * Software indicator bits 24, 25, 26, and 27 must be

	 * set.  All other Linux PTE bits control the behavior

	 * of the MMU.
@@ -469,11 +485,12 @@ DataTLBError: 
	stw	r10, 0(r0)

	stw	r11, 4(r0)



	/* First, make sure this was a store operation.

	mfspr	r11, SPRN_DSISR

	andis.	r11, r11, 0x4800	/* !translation or protection */

	bne	2f	/* branch if either is set */

	/* Only Change bit left now, do it here as it is faster

	 * than trapping to the C fault handler.

	*/

	mfspr	r10, SPRN_DSISR

	andis.	r11, r10, 0x0200	/* If set, indicates store op */

	beq	2f



	/* The EA of a data TLB miss is automatically stored in the MD_EPN

	 * register.  The EA of a data TLB error is automatically stored in
@@ -522,26 +539,12 @@ DataTLBError: 
	mfspr	r11, SPRN_MD_TWC		/* ....and get the pte address */

	lwz	r10, 0(r11)		/* Get the pte */



	andi.	r11, r10, _PAGE_RW	/* Is it writeable? */

	beq	2f			/* Bail out if not */



	/* Update 'changed', among others.

	*/

#ifdef CONFIG_SWAP

	ori	r10, r10, _PAGE_DIRTY|_PAGE_HWWRITE

	/* do not set the _PAGE_ACCESSED bit of a non-present page */

	andi.	r11, r10, _PAGE_PRESENT

	beq	4f

	ori	r10, r10, _PAGE_ACCESSED

4:

#else

	ori	r10, r10, _PAGE_DIRTY | _PAGE_ACCESSED | _PAGE_HWWRITE

#endif

	mfspr	r11, SPRN_MD_TWC		/* Get pte address again */

	stw	r10, 0(r11)		/* and update pte in table */

	xori	r10, r10, _PAGE_RW	/* RW bit is inverted */



	/* The Linux PTE won't go exactly into the MMU TLB.

	 * Software indicator bits 21, 22 and 28 must be clear.

	 * Software indicator bits 22 and 28 must be clear.

	 * Software indicator bits 24, 25, 26, and 27 must be

	 * set.  All other Linux PTE bits control the behavior

	 * of the MMU.