Commit c8bef10a authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/8xx: Refactor kernel address boundary comparison 



Now that linear and IMMR dedicated TLB handling is gone, kernel
boundary address comparison is similar in ITLB miss handler and
in DTLB miss handler.

Create a macro named compare_to_kernel_boundary.

When TASK_SIZE is strictly below 0x80000000 and PAGE_OFFSET is
above 0x80000000, it is enough to compare to 0x8000000, and this
can be done with a single instruction.

Using not. instruction, we get to use 'blt' conditional branch as
when doing a regular comparison:

0x00000000 <= addr <= 0x7fffffff ==>
0xffffffff >= NOT(addr) >= 0x80000000
The above test corresponds to a 'blt'

Otherwise, do a regular comparison using two instructions.

Signed-off-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/6312575d06a8813105e6564a3b12e1d373aa1b2f.1589866984.git.christophe.leroy@csgroup.eu
parent a0591b60

arch/powerpc/kernel/head_8xx.S

+8 −14
Original line number Diff line number Diff line
@@ -32,10 +32,15 @@ 


#include "head_32.h"



.macro compare_to_kernel_boundary scratch, addr

#if CONFIG_TASK_SIZE <= 0x80000000 && CONFIG_PAGE_OFFSET >= 0x80000000

/* By simply checking Address >= 0x80000000, we know if its a kernel address */

#define SIMPLE_KERNEL_ADDRESS		1

	not.	\scratch, \addr

#else

	rlwinm	\scratch, \addr, 16, 0xfff8

	cmpli	cr0, \scratch, PAGE_OFFSET@h

#endif

.endm



/*

 * We need an ITLB miss handler for kernel addresses if:
@@ -209,20 +214,11 @@ InstructionTLBMiss: 
	mtspr	SPRN_MD_EPN, r10

#ifdef ITLB_MISS_KERNEL

	mfcr	r11

#if defined(SIMPLE_KERNEL_ADDRESS)

	cmpi	cr0, r10, 0	/* Address >= 0x80000000 */

#else

	rlwinm	r10, r10, 16, 0xfff8

	cmpli	cr0, r10, PAGE_OFFSET@h

#endif

	compare_to_kernel_boundary r10, r10

#endif

	mfspr	r10, SPRN_M_TWB	/* Get level 1 table */

#ifdef ITLB_MISS_KERNEL

#if defined(SIMPLE_KERNEL_ADDRESS)

	bge+	3f

#else

	blt+	3f

#endif

	rlwinm	r10, r10, 0, 20, 31

	oris	r10, r10, (swapper_pg_dir - PAGE_OFFSET)@ha

3:
@@ -288,9 +284,7 @@ DataStoreTLBMiss: 
	 * kernel page tables.

	 */

	mfspr	r10, SPRN_MD_EPN

	rlwinm	r10, r10, 16, 0xfff8

	cmpli	cr0, r10, PAGE_OFFSET@h



	compare_to_kernel_boundary r10, r10

	mfspr	r10, SPRN_M_TWB	/* Get level 1 table */

	blt+	3f

	rlwinm	r10, r10, 0, 20, 31