diff options
| author | Marc Zyngier <maz@kernel.org> | 2019-10-02 11:06:12 +0200 |
|---|---|---|
| committer | Catalin Marinas <catalin.marinas@arm.com> | 2019-10-15 13:26:09 +0200 |
| commit | f226650494c6aa87526d12135b7de8b8c074f3de (patch) | |
| tree | 1c00f90dac02fdb1240153bab7a9faa8565aa52a /arch/arm64/kernel/entry.S | |
| parent | Linux 5.4-rc3 (diff) | |
| download | linux-f226650494c6aa87526d12135b7de8b8c074f3de.tar.xz linux-f226650494c6aa87526d12135b7de8b8c074f3de.zip | |
arm64: Relax ICC_PMR_EL1 accesses when ICC_CTLR_EL1.PMHE is clear
The GICv3 architecture specification is incredibly misleading when it
comes to PMR and the requirement for a DSB. It turns out that this DSB
is only required if the CPU interface sends an Upstream Control
message to the redistributor in order to update the RD's view of PMR.
This message is only sent when ICC_CTLR_EL1.PMHE is set, which isn't
the case in Linux. It can still be set from EL3, so some special care
is required. But the upshot is that in the (hopefuly large) majority
of the cases, we can drop the DSB altogether.
This relies on a new static key being set if the boot CPU has PMHE
set. The drawback is that this static key has to be exported to
modules.
Cc: Will Deacon <will@kernel.org>
Cc: James Morse <james.morse@arm.com>
Cc: Julien Thierry <julien.thierry.kdev@gmail.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Diffstat (limited to 'arch/arm64/kernel/entry.S')
| -rw-r--r-- | arch/arm64/kernel/entry.S | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index e304fe04b098..0a44f21bf087 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -269,8 +269,10 @@ alternative_else_nop_endif alternative_if ARM64_HAS_IRQ_PRIO_MASKING ldr x20, [sp, #S_PMR_SAVE] msr_s SYS_ICC_PMR_EL1, x20 - /* Ensure priority change is seen by redistributor */ - dsb sy + mrs_s x21, SYS_ICC_CTLR_EL1 + tbz x21, #6, .L__skip_pmr_sync\@ // Check for ICC_CTLR_EL1.PMHE + dsb sy // Ensure priority change is seen by redistributor +.L__skip_pmr_sync\@: alternative_else_nop_endif ldp x21, x22, [sp, #S_PC] // load ELR, SPSR |