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arm64: Relax ICC_PMR_EL1 accesses when ICC_CTLR_EL1.PMHE is clear

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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>
This commit is contained in:
Marc Zyngier
2019-10-02 10:06:12 +01:00
committed by Catalin Marinas
parent 4f5cafb5cb
commit f226650494
8 changed files with 53 additions and 16 deletions
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2
include/linux/irqchip/arm-gic-v3.h
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@@ -487,6 +487,8 @@
#define ICC_CTLR_EL1_EOImode_MASK (1 << ICC_CTLR_EL1_EOImode_SHIFT)
#define ICC_CTLR_EL1_CBPR_SHIFT 0
#define ICC_CTLR_EL1_CBPR_MASK (1 << ICC_CTLR_EL1_CBPR_SHIFT)
#define ICC_CTLR_EL1_PMHE_SHIFT 6
#define ICC_CTLR_EL1_PMHE_MASK (1 << ICC_CTLR_EL1_PMHE_SHIFT)
#define ICC_CTLR_EL1_PRI_BITS_SHIFT 8
#define ICC_CTLR_EL1_PRI_BITS_MASK (0x7 << ICC_CTLR_EL1_PRI_BITS_SHIFT)
#define ICC_CTLR_EL1_ID_BITS_SHIFT 11