• Marc Zyngier's avatar
    arm64: Relax ICC_PMR_EL1 accesses when ICC_CTLR_EL1.PMHE is clear · f2266504
    Marc Zyngier authored
    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: default avatarMarc Zyngier <maz@kernel.org>
    Signed-off-by: default avatarCatalin Marinas <catalin.marinas@arm.com>
    f2266504
irqflags.h 2.82 KB