[PATCH v8 0/7] RISC-V IPI Improvements

[Anup Patel]

This series aims to improve IPI support in Linux RISC-V in following ways:
 1) Treat IPIs as normal per-CPU interrupts instead of having custom RISC-V
    specific hooks. This also makes Linux RISC-V IPI support aligned with
    other architectures.
 2) Remote TLB flushes and icache flushes should prefer local IPIs instead
    of SBI calls whenever we have specialized hardware (such as RISC-V AIA
    IMSIC and RISC-V SWI) which allows S-mode software to directly inject
    IPIs without any assistance from M-mode runtime firmware.

These patches were originally part of the "Linux RISC-V ACLINT Support"
series but this now a separate series so that it can be merged independently
of the "Linux RISC-V ACLINT Support" series.
(Refer, https://lore.kernel.org/lkml/20211007123632.697666-1-anup.patel@wdc.com/)

These patches are also a preparatory patches for the up-coming:
 1) Linux RISC-V AIA support
 2) Linux RISC-V SWI support

These patches can also be found in riscv_ipi_imp_v8 branch at:
https://github.com/avpatel/linux.git

Changes since v7:
 - Rebased on Linux-6.0-rc1
 - Use atomic operations to track per-CPU pending and enabled IPIs in PATCH3.
   (Note: this is inspired from IPI muxing implemented in
    drivers/irqchip/irq-apple-aic.c)
 - Made "struct ipi_mux_ops" (added by PATCH3) flexible so that
   drivers/irqchip/irq-apple-aic.c can adopt it in future.

Changes since v6:
 - Rebased on Linux-5.19-rc7
 - Added documentation for struct ipi_mux_ops in PATCH3
 - Dropped dummy irq_mask()/unmask() in PATCH3
 - Added const for "ipi_mux_chip" in PATCH3
 - Removed "type" initialization from ipi_mux_domain_alloc() in PATCH3
 - Dropped translate() from "ipi_mux_domain_ops" in PATCH3
 - Improved barrier documentation in ipi_mux_process() of PATCH3
 - Added percpu check in ipi_mux_create() for parent_virq of PATCH3
 - Added nr_ipi parameter in ipi_mux_create() of PATCH3

Changes since v5:
 - Rebased on Linux-5.18-rc3
 - Used kernel doc style in PATCH3
 - Removed redundant loop in ipi_mux_process() of PATCH3
 - Removed "RISC-V" prefix form ipi_mux_chip.name of PATCH3
 - Removed use of "this patch" in PATCH3 commit description
 - Addressed few other nit comments in PATCH3

Changes since v4:
 - Rebased on Linux-5.17
 - Includes new PATCH3 which adds mechanism to multiplex a single HW IPI

Changes since v3:
 - Rebased on Linux-5.17-rc6
 - Updated PATCH2 to not export riscv_set_intc_hwnode_fn()
 - Simplified riscv_intc_hwnode() in PATCH2

Changes since v2:
 - Rebased on Linux-5.17-rc4
 - Updated PATCH2 to not create synthetic INTC fwnode and instead provide
   a function which allows drivers to directly discover INTC fwnode

Changes since v1:
 - Use synthetic fwnode for INTC instead of irq_set_default_host() in PATCH2

Anup Patel (7):
  RISC-V: Clear SIP bit only when using SBI IPI operations
  irqchip/riscv-intc: Allow drivers to directly discover INTC hwnode
  genirq: Add mechanism to multiplex a single HW IPI
  RISC-V: Treat IPIs as normal Linux IRQs
  RISC-V: Allow marking IPIs as suitable for remote FENCEs
  RISC-V: Use IPIs for remote TLB flush when possible
  RISC-V: Use IPIs for remote icache flush when possible

 arch/riscv/Kconfig                |   2 +
 arch/riscv/include/asm/irq.h      |   4 +
 arch/riscv/include/asm/sbi.h      |   7 +
 arch/riscv/include/asm/smp.h      |  49 ++++--
 arch/riscv/kernel/Makefile        |   1 +
 arch/riscv/kernel/cpu-hotplug.c   |   3 +-
 arch/riscv/kernel/irq.c           |  21 ++-
 arch/riscv/kernel/sbi-ipi.c       |  60 ++++++++
 arch/riscv/kernel/sbi.c           |  11 --
 arch/riscv/kernel/smp.c           | 164 ++++++++++----------
 arch/riscv/kernel/smpboot.c       |   5 +-
 arch/riscv/mm/cacheflush.c        |   5 +-
 arch/riscv/mm/tlbflush.c          |  93 ++++++++++--
 drivers/clocksource/timer-clint.c |  42 +++--
 drivers/irqchip/irq-riscv-intc.c  |  60 ++++----
 include/linux/irq.h               |  18 +++
 kernel/irq/Kconfig                |   5 +
 kernel/irq/Makefile               |   1 +
 kernel/irq/ipi-mux.c              | 244 ++++++++++++++++++++++++++++++
 19 files changed, 628 insertions(+), 167 deletions(-)
 create mode 100644 arch/riscv/kernel/sbi-ipi.c
 create mode 100644 kernel/irq/ipi-mux.c

-- 
2.34.1