| Message ID | 20210714014113.4004878-1-pcc@google.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] arm64: avoid double ISB on kernel entry | expand |
On Tue, Jul 13, 2021 at 06:41:13PM -0700, Peter Collingbourne wrote: > 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 > --- > v2: > - fix formatting > > arch/arm64/kernel/entry.S | 15 +++++++++++++-- > 1 file changed, 13 insertions(+), 2 deletions(-) Thanks for the quick respin: Acked-by: Will Deacon <will@kernel.org> Will
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 2d6dc62d929a..8d63161cad8c 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -191,7 +191,6 @@ alternative_else_nop_endif ldr_l \tmp, gcr_kernel_excl mte_set_gcr \tmp, \tmp2 - isb 1: #endif .endm @@ -265,12 +264,24 @@ alternative_if ARM64_HAS_ADDRESS_AUTH orr x0, x0, SCTLR_ELx_ENIA msr sctlr_el1, x0 2: - isb alternative_else_nop_endif #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, #PT_REGS_SIZE
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 --- v2: - fix formatting arch/arm64/kernel/entry.S | 15 +++++++++++++-- 1 file changed, 13 insertions(+), 2 deletions(-)