[RFC 0/7] arm64: provide pseudo NMI with GICv3

[Julien Thierry]

Gentle ping on this series.

On 11/10/17 14:00, Julien Thierry wrote:
> Hi,
> 
> This series is a continuation of the work started by Daniel [1]. The goal is
> to use GICv3 interrupt priorities to simulate an NMI.
> 
> To achieve this, set two priorities, one for standard interrupts and
> another, higher priority, for NMIs. Whenever we want to disable interrupts,
> we mask the standard priority instead so NMIs can still be raised. Some
> corner cases though still require to actually mask all interrupts
> effectively disabling the NMI.
> 
> Of course, using priority masking instead of PSR.I comes at some cost. On
> hackbench, I notice a ~6% drop of performance. However, on a kernel build,
> I do not see significant differences.
> 
> Currently, only PPIs and SPIs can be set as NMIs. IPIs being currently
> hardcoded IRQ numbers, there isn't a generic interface to set SGIs as NMI
> for now. I don't think there is any reason LPIs should be allowed to be set
> as NMI as they do not have an active state.
> When an NMI is active on a CPU, no other NMI can be triggered on the CPU.
> 
> Requirements to use this:
> - Have GICv3
> - SCR_EL3.FIQ is set to 1 when linux runs
> - Select Kernel Feature -> Use ICC system registers for IRQ masking
> 
>  From my testing with the perf interrupt, there doesn't seem to be any major
> issue left (but if you find some, do tell!).
> 
> * Patches 1 and 5 are minor utility changes.
> * Patches 2 and 3 allows to detect and enable the use of GICv3 system
>    registers during boot time.
> * Patch 4 introduces the masking of IRQs using priorities replacing irq
>    disabling.
> * Patch 6 add detection of the view linux has on GICv3 priorities, without
>    this we cannot easily mask specific priorities in an accurate manner
> * Patch 7 adds the support for NMIs
> 
> 
> [1] http://www.spinics.net/lists/arm-kernel/msg525077.html
> 
> Thanks,
> 
> Julien Thierry
> 
> 
> Daniel Thompson (4):
>    arm64: irqflags: Reorder the fiq & async macros
>    arm64: cpufeature: Allow early detect of specific features
>    arm64: alternative: Apply alternatives early in boot process
>    arm64: irqflags: Use ICC sysregs to implement IRQ masking
> 
> Julien Thierry (3):
>    irqchip/gic: Add functions to access irq priorities
>    arm64: Detect current view of GIC priorities
>    arm64: Add support for pseudo-NMIs
> 
>   Documentation/arm64/booting.txt        |   5 +
>   arch/arm64/Kconfig                     |  15 ++
>   arch/arm64/include/asm/alternative.h   |   1 +
>   arch/arm64/include/asm/arch_gicv3.h    |  24 +++
>   arch/arm64/include/asm/assembler.h     |  33 +++-
>   arch/arm64/include/asm/efi.h           |   5 +
>   arch/arm64/include/asm/irqflags.h      | 143 +++++++++++++++-
>   arch/arm64/include/asm/kvm_host.h      |  40 +++++
>   arch/arm64/include/asm/processor.h     |   4 +
>   arch/arm64/include/asm/ptrace.h        |  14 +-
>   arch/arm64/include/asm/sysreg.h        |   1 +
>   arch/arm64/kernel/alternative.c        |  39 ++++-
>   arch/arm64/kernel/asm-offsets.c        |   1 +
>   arch/arm64/kernel/cpufeature.c         |  67 +++++---
>   arch/arm64/kernel/entry.S              | 132 ++++++++++++--
>   arch/arm64/kernel/head.S               |  38 +++++
>   arch/arm64/kernel/process.c            |   6 +
>   arch/arm64/kernel/smp.c                |  14 ++
>   arch/arm64/mm/proc.S                   |  23 +++
>   drivers/irqchip/irq-gic-common.c       |  10 ++
>   drivers/irqchip/irq-gic-common.h       |   2 +
>   drivers/irqchip/irq-gic-v3-its.c       |   2 +-
>   drivers/irqchip/irq-gic-v3.c           | 304 +++++++++++++++++++++++++++++----
>   include/linux/interrupt.h              |   1 +
>   include/linux/irqchip/arm-gic-common.h |   6 +
>   include/linux/irqchip/arm-gic.h        |   5 -
>   26 files changed, 845 insertions(+), 90 deletions(-)
> 
> --
> 1.9.1
> 

-- 
Julien Thierry