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FROMLIST: arm64: avoid double ISB on kernel entry

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Although an ISB is required in order to make the MTE-related system
register update to GCR_EL1 effective, and the same is true for
PAC-related updates to SCTLR_EL1 or APIAKey{Hi,Lo}_EL1, we issue two
ISBs on machines that support both features while we only need to
issue one. To avoid the unnecessary additional ISB, remove the ISBs
from the PAC and MTE-specific alternative blocks and add a couple
of additional blocks that cause us to only execute one ISB if both
features are supported.

Signed-off-by: Peter Collingbourne <pcc@google.com>
Link: https://linux-review.googlesource.com/id/Idee7e8114d5ae5a0b171d06220a0eb4bb015a51c
Change-Id: Idee7e8114d5ae5a0b171d06220a0eb4bb015a51c
Bug: 192536783
Link: https://lore.kernel.org/linux-arm-kernel/20210714013631.3994485-1-pcc@google.com/T/
This commit is contained in:
Peter Collingbourne 2021-07-13 18:22:25 -07:00 committed by Todd Kjos
parent 98b2c1dd1c
commit ec2190fd3f
1 changed files with 13 additions and 2 deletions
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15
arch/arm64/kernel/entry.S
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@ -199,7 +199,6 @@ alternative_else_nop_endif
ldr_l \tmp, gcr_kernel_excl
mte_set_gcr \tmp, \tmp2
isb
1:
#endif
.endm
@ -272,7 +271,6 @@ alternative_if ARM64_HAS_ADDRESS_AUTH
orr x0, x0, SCTLR_ELx_ENIA
msr sctlr_el1, x0
2:
isb
alternative_else_nop_endif
#endif
@ -280,6 +278,19 @@ alternative_else_nop_endif
mte_set_kernel_gcr x22, x23
/*
* Any non-self-synchronizing system register updates required for
* kernel entry should be placed before this point.
*/
alternative_if ARM64_MTE
isb
b 1f
alternative_else_nop_endif
alternative_if ARM64_HAS_ADDRESS_AUTH
isb
alternative_else_nop_endif
1:
scs_load tsk, x20
.else
add x21, sp, #S_FRAME_SIZE