Commit 863771a2 authored by Christophe Leroy's avatar Christophe Leroy Committed by Michael Ellerman
Browse files

powerpc/32s: Convert switch_mmu_context() to C 



switch_mmu_context() does things that can easily be done in C.

For updating user segments, we have update_user_segments().

As mentionned in commit b5efec00 ("powerpc/32s: Move KUEP
locking/unlocking in C"), update_user_segments() has the loop
unrolled which is a significant performance gain.

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/05c0875ad8220c03452c3a334946e207c6ca04d6.1622708530.git.christophe.leroy@csgroup.eu
parent 7235bb35

arch/powerpc/include/asm/book3s/32/kup.h

+5 −0
Original line number Diff line number Diff line
@@ -7,6 +7,11 @@ 


#ifndef __ASSEMBLY__



static __always_inline bool kuap_is_disabled(void)

{

	return !IS_ENABLED(CONFIG_PPC_KUAP);

}



static __always_inline bool kuep_is_disabled(void)

{

	return !IS_ENABLED(CONFIG_PPC_KUEP);

arch/powerpc/kernel/asm-offsets.c

+0 −5
Original line number Diff line number Diff line
@@ -86,7 +86,6 @@ int main(void) 
	OFFSET(PACA_CANARY, paca_struct, canary);

#endif

#endif

	OFFSET(MMCONTEXTID, mm_struct, context.id);

#ifdef CONFIG_PPC32

#ifdef CONFIG_PPC_RTAS

	OFFSET(RTAS_SP, thread_struct, rtas_sp);
@@ -323,10 +322,6 @@ int main(void) 
#endif

#endif



#ifndef CONFIG_PPC64

	OFFSET(MM_PGD, mm_struct, pgd);

#endif /* ! CONFIG_PPC64 */



	/* About the CPU features table */

	OFFSET(CPU_SPEC_FEATURES, cpu_spec, cpu_features);

	OFFSET(CPU_SPEC_SETUP, cpu_spec, cpu_setup);

arch/powerpc/kernel/head_book3s_32.S

+0 −58
Original line number Diff line number Diff line
@@ -1033,58 +1033,6 @@ END_MMU_FTR_SECTION_IFCLR(MMU_FTR_HPTE_TABLE) 
	mtspr	SPRN_SRR1,r4

	rfi



/*

 * void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next);

 *

 * Set up the segment registers for a new context.

 */

_ENTRY(switch_mmu_context)

	lwz	r3,MMCONTEXTID(r4)

	cmpwi	cr0,r3,0

	blt-	4f

	mulli	r3,r3,897	/* multiply context by skew factor */

	rlwinm	r3,r3,4,8,27	/* VSID = (context & 0xfffff) << 4 */

#ifdef CONFIG_PPC_KUEP

	oris	r3, r3, SR_NX@h	/* Set Nx */

#endif

#ifdef CONFIG_PPC_KUAP

	oris	r3, r3, SR_KS@h	/* Set Ks */

#endif

	li	r0,NUM_USER_SEGMENTS

	mtctr	r0



#ifdef CONFIG_BDI_SWITCH

	/* Context switch the PTE pointer for the Abatron BDI2000.

	 * The PGDIR is passed as second argument.

	 */

	lwz	r4, MM_PGD(r4)

	lis	r5, abatron_pteptrs@ha

	stw	r4, abatron_pteptrs@l + 0x4(r5)

#endif

BEGIN_MMU_FTR_SECTION

#ifndef CONFIG_BDI_SWITCH

	lwz	r4, MM_PGD(r4)

#endif

	tophys(r4, r4)

	rlwinm	r4, r4, 4, 0xffff01ff

	mtspr	SPRN_SDR1, r4

END_MMU_FTR_SECTION_IFCLR(MMU_FTR_HPTE_TABLE)

	li	r4,0

	isync

3:

	mtsrin	r3,r4

	addi	r3,r3,0x111	/* next VSID */

	rlwinm	r3,r3,0,8,3	/* clear out any overflow from VSID field */

	addis	r4,r4,0x1000	/* address of next segment */

	bdnz	3b

	sync

	isync

	blr

4:	trap

	EMIT_BUG_ENTRY 4b,__FILE__,__LINE__,0

	blr

EXPORT_SYMBOL(switch_mmu_context)



/*

 * An undocumented "feature" of 604e requires that the v bit

 * be cleared before changing BAT values.
@@ -1282,9 +1230,3 @@ EXPORT_SYMBOL(empty_zero_page) 
	.globl	swapper_pg_dir

swapper_pg_dir:

	.space	PGD_TABLE_SIZE
 


/* Room for two PTE pointers, usually the kernel and current user pointers

 * to their respective root page table.

 */

abatron_pteptrs:

	.space	8

arch/powerpc/mm/book3s32/mmu_context.c

+35 −0
Original line number Diff line number Diff line
@@ -23,6 +23,12 @@ 


#include <asm/mmu_context.h>



/*

 * Room for two PTE pointers, usually the kernel and current user pointers

 * to their respective root page table.

 */

void *abatron_pteptrs[2];



/*

 * On 32-bit PowerPC 6xx/7xx/7xxx CPUs, we use a set of 16 VSIDs

 * (virtual segment identifiers) for each context.  Although the
@@ -98,3 +104,32 @@ void __init mmu_context_init(void) 
	context_map[0] = (1 << FIRST_CONTEXT) - 1;

	next_mmu_context = FIRST_CONTEXT;

}



void switch_mmu_context(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk)

{

	long id = next->context.id;

	unsigned long val;



	if (id < 0)

		panic("mm_struct %p has no context ID", next);



	isync();



	val = CTX_TO_VSID(id, 0);

	if (!kuep_is_disabled())

		val |= SR_NX;

	if (!kuap_is_disabled())

		val |= SR_KS;



	update_user_segments(val);



	if (IS_ENABLED(CONFIG_BDI_SWITCH))

		abatron_pteptrs[1] = next->pgd;



	if (!mmu_has_feature(MMU_FTR_HPTE_TABLE))

		mtspr(SPRN_SDR1, rol32(__pa(next->pgd), 4) & 0xffff01ff);



	mb();	/* sync */

	isync();

}

EXPORT_SYMBOL(switch_mmu_context);