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ARM: 9199/1: spectre-bhb: use local DSB and elide ISB in loop8 sequence 

The loop8 mitigation for Spectre-BHB only requires a CPU local DSB
rather than a systemwide one, which is much more costly. And by the same
reasoning as why it is justified to omit the ISB after BPIALL, we can
also elide the ISB and rely on the exception return for the context
synchronization.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Ard Biesheuvel 2022-04-20 09:57:45 +01:00 committed by Russell King (Oracle)
parent c4f486f1e7
commit 892c608a7d
2 changed files with 4 additions and 3 deletions
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5
arch/arm/kernel/entry-armv.S
View File

@ -1131,8 +1131,9 @@ vector_bhb_loop8_\name:
3: W(b) . + 4
subs r0, r0, #1
bne 3b
dsb
isb
dsb nsh
@ isb not needed due to "movs pc, lr" in the vector stub
@ which gives a "context synchronisation".
b 2b
ENDPROC(vector_bhb_loop8_\name)
.previous

2
arch/arm/kernel/entry-common.S
View File

@ -164,7 +164,7 @@ ENTRY(vector_bhb_loop8_swi)
1: b 2f
2: subs r8, r8, #1
bne 1b
dsb
dsb nsh
isb
b 3f
ENDPROC(vector_bhb_loop8_swi)