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Revert "powerpc/8xx: Always pin kernel text TLB"

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This reverts commit bccc58986a.

When STRICT_KERNEL_RWX is selected, EXEC memory must stop where
RW memory start. When pinning iTLBs it means an 8M alignment for
RW data start. That may be acceptable on boards with a lot of
memory but one of my supported boards only has 32 Mbytes and this
forced alignment leads to a waste of almost 4 Mbytes with is more
than 10% of the total memory.

So revert commit bccc58986a ("powerpc/8xx: Always pin kernel text
TLB") but don't restore previous behaviour in ITLB miss handler
as now kernel PGD entries are copied into each process PGDIR.

Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/01b6780b860c8043b51a1ba9d83acfc6f2dde910.1724173828.git.christophe.leroy@csgroup.eu
This commit is contained in:
Christophe Leroy 2024-08-20 19:23:48 +02:00 committed by Michael Ellerman
parent 985db026c3
commit 1a736d98c8
3 changed files with 17 additions and 1 deletions
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8
arch/powerpc/kernel/head_8xx.S
View file

@ -587,6 +587,10 @@ start_here:
lis r0, (MD_TWAM | MD_RSV4I)@h
mtspr SPRN_MD_CTR, r0
#endif
#ifndef CONFIG_PIN_TLB_TEXT
li r0, 0
mtspr SPRN_MI_CTR, r0
#endif
#if !defined(CONFIG_PIN_TLB_DATA) && !defined(CONFIG_PIN_TLB_IMMR)
lis r0, MD_TWAM@h
mtspr SPRN_MD_CTR, r0
@ -683,6 +687,7 @@ SYM_FUNC_START_LOCAL(initial_mmu)
blr
SYM_FUNC_END(initial_mmu)
#ifdef CONFIG_PIN_TLB
_GLOBAL(mmu_pin_tlb)
lis r9, (1f - PAGE_OFFSET)@h
ori r9, r9, (1f - PAGE_OFFSET)@l
@ -704,6 +709,7 @@ _GLOBAL(mmu_pin_tlb)
mtspr SPRN_MD_CTR, r6
tlbia
#ifdef CONFIG_PIN_TLB_TEXT
LOAD_REG_IMMEDIATE(r5, 28 << 8)
LOAD_REG_IMMEDIATE(r6, PAGE_OFFSET)
LOAD_REG_IMMEDIATE(r7, MI_SVALID | MI_PS8MEG | _PMD_ACCESSED)
@ -724,6 +730,7 @@ _GLOBAL(mmu_pin_tlb)
bdnzt lt, 2b
lis r0, MI_RSV4I@h
mtspr SPRN_MI_CTR, r0
#endif
LOAD_REG_IMMEDIATE(r5, 28 << 8 | MD_TWAM)
#ifdef CONFIG_PIN_TLB_DATA
@ -783,3 +790,4 @@ _GLOBAL(mmu_pin_tlb)
mtspr SPRN_SRR1, r10
mtspr SPRN_SRR0, r11
rfi
#endif

3
arch/powerpc/mm/nohash/8xx.c
View file

@ -177,7 +177,8 @@ int mmu_mark_initmem_nx(void)
if (!debug_pagealloc_enabled_or_kfence())
err = mmu_mapin_ram_chunk(boundary, einittext8, PAGE_KERNEL, false);
mmu_pin_tlb(block_mapped_ram, false);
if (IS_ENABLED(CONFIG_PIN_TLB_TEXT))
mmu_pin_tlb(block_mapped_ram, false);
return err;
}

7
arch/powerpc/platforms/8xx/Kconfig
View file

@ -195,6 +195,13 @@ config PIN_TLB_IMMR
CONFIG_PIN_TLB_DATA is also selected, it will reduce
CONFIG_PIN_TLB_DATA to 24 Mbytes.
config PIN_TLB_TEXT
bool "Pinned TLB for TEXT"
depends on PIN_TLB
default y
help
This pins kernel text with 8M pages.
endmenu
endmenu