[PATCH v5 0/7] RISC-V IPI Improvements

Anup Patel
2022-03-24T15:14:06Z

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) KVM RISC-V TLB flush improvements
3) Linux RISC-V SWI support

These patches can also be found in riscv_ipi_imp_v5 branch at:
https://github.com/avpatel/linux.git

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 | 2 +
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 | 41 +++++--
drivers/irqchip/irq-riscv-intc.c | 60 +++++-----
include/linux/irq.h | 28 +++++
kernel/irq/Kconfig | 4 +
kernel/irq/Makefile | 1 +
kernel/irq/ipi-mux.c | 190 ++++++++++++++++++++++++++++++
19 files changed, 577 insertions(+), 167 deletions(-)
create mode 100644 arch/riscv/kernel/sbi-ipi.c
create mode 100644 kernel/irq/ipi-mux.c

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2.25.1