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| author |   Marc Zyngier <maz@kernel.org> | 2019-10-02 10:06:12 +0100 |
|---|---|---|
| committer |   Catalin Marinas <catalin.marinas@arm.com> | 2019-10-15 12:26:09 +0100 |
| commit | f226650494c6aa87526d12135b7de8b8c074f3de (patch) | |
| tree | 1c00f90dac02fdb1240153bab7a9faa8565aa52a /drivers/irqchip | |
| parent | Linux 5.4-rc3 (diff) | |
| download | linux-dev-f226650494c6aa87526d12135b7de8b8c074f3de.tar.xz linux-dev-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 'drivers/irqchip')
| -rw-r--r-- | drivers/irqchip/irq-gic-v3.c | 20 |
1 files changed, 20 insertions, 0 deletions
diff --git a/drivers/irqchip/irq-gic-v3.c b/drivers/irqchip/irq-gic-v3.c index 422664ac5f53..0abc5a13adaa 100644 --- a/drivers/irqchip/irq-gic-v3.c +++ b/drivers/irqchip/irq-gic-v3.c @@ -87,6 +87,15 @@ static DEFINE_STATIC_KEY_TRUE(supports_deactivate_key); */ static DEFINE_STATIC_KEY_FALSE(supports_pseudo_nmis); +/* + * Global static key controlling whether an update to PMR allowing more + * interrupts requires to be propagated to the redistributor (DSB SY). + * And this needs to be exported for modules to be able to enable + * interrupts... + */ +DEFINE_STATIC_KEY_FALSE(gic_pmr_sync); +EXPORT_SYMBOL(gic_pmr_sync); + /* ppi_nmi_refs[n] == number of cpus having ppi[n + 16] set as NMI */ static refcount_t *ppi_nmi_refs; @@ -1502,6 +1511,17 @@ static void gic_enable_nmi_support(void) for (i = 0; i < gic_data.ppi_nr; i++) refcount_set(&ppi_nmi_refs[i], 0); + /* + * Linux itself doesn't use 1:N distribution, so has no need to + * set PMHE. The only reason to have it set is if EL3 requires it + * (and we can't change it). + */ + if (gic_read_ctlr() & ICC_CTLR_EL1_PMHE_MASK) + static_branch_enable(&gic_pmr_sync); + + pr_info("%s ICC_PMR_EL1 synchronisation\n", + static_branch_unlikely(&gic_pmr_sync) ? "Forcing" : "Relaxing"); + static_branch_enable(&supports_pseudo_nmis); if (static_branch_likely(&supports_deactivate_key)) |