Re: [PATCH v18 0/7] RISC-V IPI Improvements

Anup Patel
2023-03-28T03:57:21Z

Hi Marc and Palmer,

On Tue, Mar 28, 2023 at 9:22 AM Anup Patel <apatel@ventanamicro.com> wrote:
>
> 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_v18 branch at:
> https://github.com/avpatel/linux.git
>
> Changes since v17:
> - Resolved merge conflicts and rebased on Linux-6.3-rc4
>
> Changes since v16:
> - Rebased on Linux-6.3-rc1
> - Dropped PATCH3 and PATCH9 since these patches are already merged
> - Added Palmer's Acked-by
>
> Changes since v15:
> - Rebased on Linux-6.2-rc2
> - Added Reviewed-by and Tested-by tags to some of the patches.
>
> Changes since v14:
> - Minor fixes in commit description of PATCH3 (as suggested by tglx)
> - Don't disable parent IPI when CPU goes offline for SBI IPI driver and
> CLINT driver in PATCH4.
> - Include Apple AIC driver changes from Marc Z as PATCH9
>
> Changes since v13:
> - Included changes suggested by Marc Z in PATCH3
> - Use chained handlers in PATCH4
> - Added new PATCH8 to have empty irq_eoi() in RISC-V INTC driver. This
> avoids the unnecessary mask/unmask dance at time of handling interrupts.
>
> Changes since v12:
> - Rebased on Linux-6.1-rc7
> - Bring-back the IPI optimization in ipi_mux_send_mask() for PATCH3
> - Call ipi_mux_send() for one target CPU at a time in PATCH3
>
> Changes since v11:
> - Removed ipi_mux_pre/post_handle() callbacks in PATCH3
> - Removed sturct ipi_mux_ops in PATCH3
> - Removed parent_virq and data pointer from everywhere in PATCH3
> - Removed struct ipi_mux_control in PATCH3
> - Improved function signature of ipi_mux_send() callback in PATCH3
> - Used unsigned type with atomic operation in PATCH3
>
> Changes since v10:
> - Rebased on Linux-6.1-rc5
> - Drop the "!(pending & ibit)" check in ipi_mux_send_mask() of PATCH3
> - Disable local interrupts in ipi_mux_send_mask() of PATCH3 because we
> can be preempted while using a per-CPU temporary variable.
>
> Changes since v9:
> - Rebased on Linux-6.1-rc3
> - Updated header comment block of ipi-mux.c in PATCH3
> - Use a struct for global data of ipi-mux.c in PATCH3
> - Add per-CPU temp cpumask for sending IPIs in PATCH3
> - Drop the use of fwspec in PATCH3
> - Use static key for ipi_mux_pre_handle() and ipi_mux_post_handle()
> in PATCH3
> - Remove redundant pr_warn_ratelimited() called by ipi_mux_process()
> in PATCH3
> - Remove CPUHP thingy from ipi_mux_create() in PATCH3
>
> Changes since v8:
> - Rebased on Linux-6.0-rc3
> - Use dummy percpu data as parameter for request_percpu_irq() in PATCH4.
>
> 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
> 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
> irqchip/riscv-intc: Add empty irq_eoi() for chained irq handlers

There were merge conflicts with Linux-6.3-rc4 which are resolved
in this series.

It would be great if this series can be considered for Linux-6.4

Thanks,
Anup

>
> arch/riscv/Kconfig | 2 +
> arch/riscv/include/asm/irq.h | 4 +
> arch/riscv/include/asm/sbi.h | 9 +-
> 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 | 77 ++++++++++++++
> arch/riscv/kernel/sbi.c | 100 +++--------------
> arch/riscv/kernel/smp.c | 171 +++++++++++++++---------------
> arch/riscv/kernel/smpboot.c | 5 +-
> arch/riscv/mm/cacheflush.c | 5 +-
> arch/riscv/mm/tlbflush.c | 93 +++++++++++++---
> drivers/clocksource/timer-clint.c | 65 +++++++++---
> drivers/irqchip/Kconfig | 1 +
> drivers/irqchip/irq-riscv-intc.c | 71 ++++++++-----
> 16 files changed, 429 insertions(+), 248 deletions(-)
> create mode 100644 arch/riscv/kernel/sbi-ipi.c
>
> --
> 2.34.1
>