Message-ID: <874ixfhzr4.fsf@all.your.base.are.belong.to.us>
Date: Tue, 20 May 2025 21:02:23 +0200
From: Björn Töpel <bjorn@...nel.org>
To: Clément Léger <cleger@...osinc.com>, Paul Walmsley
 <paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>,
 linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
 linux-arm-kernel@...ts.infradead.org
Cc: Clément Léger <cleger@...osinc.com>, Himanshu
 Chauhan
 <hchauhan@...tanamicro.com>, Anup Patel <apatel@...tanamicro.com>, Xu Lu
 <luxu.kernel@...edance.com>, Atish Patra <atishp@...shpatra.org>, Conor
 Dooley <conor.dooley@...rochip.com>
Subject: Re: [PATCH v4 3/4] drivers: firmware: add riscv SSE support

Clément Léger <cleger@...osinc.com> writes:

> Add driver level interface to use RISC-V SSE arch support. This interface
> allows registering SSE handlers, and receive them. This will be used by
> PMU and GHES driver.
>
> Signed-off-by: Himanshu Chauhan <hchauhan@...tanamicro.com>
> Co-developed-by: Himanshu Chauhan <hchauhan@...tanamicro.com>
> Signed-off-by: Clément Léger <cleger@...osinc.com>
> Acked-by: Conor Dooley <conor.dooley@...rochip.com>
> ---
>  MAINTAINERS                        |  15 +
>  drivers/firmware/Kconfig           |   1 +
>  drivers/firmware/Makefile          |   1 +
>  drivers/firmware/riscv/Kconfig     |  15 +
>  drivers/firmware/riscv/Makefile    |   3 +
>  drivers/firmware/riscv/riscv_sse.c | 696 +++++++++++++++++++++++++++++
>  include/linux/riscv_sse.h          |  59 +++
>  7 files changed, 790 insertions(+)
>  create mode 100644 drivers/firmware/riscv/Kconfig
>  create mode 100644 drivers/firmware/riscv/Makefile
>  create mode 100644 drivers/firmware/riscv/riscv_sse.c
>  create mode 100644 include/linux/riscv_sse.h
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 3563492e4eba..ae21147bf71d 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -20892,6 +20892,13 @@ T:	git git://git.kernel.org/pub/scm/linux/kernel/git/iommu/linux.git
>  F:	Documentation/devicetree/bindings/iommu/riscv,iommu.yaml
>  F:	drivers/iommu/riscv/
>  
> +RISC-V FIRMWARE DRIVERS
> +M:	Conor Dooley <conor@...nel.org>
> +L:	linux-riscv@...ts.infradead.org
> +S:	Maintained
> +T:	git git://git.kernel.org/pub/scm/linux/kernel/git/conor/linux.git
> +F:	drivers/firmware/riscv/*
> +
>  RISC-V MICROCHIP FPGA SUPPORT
>  M:	Conor Dooley <conor.dooley@...rochip.com>
>  M:	Daire McNamara <daire.mcnamara@...rochip.com>
> @@ -20956,6 +20963,14 @@ F:	arch/riscv/boot/dts/spacemit/
>  N:	spacemit
>  K:	spacemit
>  
> +RISC-V SSE DRIVER
> +M:	Clément Léger <cleger@...osinc.com>
> +R:	Himanshu Chauhan <himanshu@...chauhan.dev>
> +L:	linux-riscv@...ts.infradead.org
> +S:	Maintained
> +F:	drivers/firmware/riscv/riscv_sse.c
> +F:	include/linux/riscv_sse.h
> +
>  RISC-V THEAD SoC SUPPORT
>  M:	Drew Fustini <drew@...7.com>
>  M:	Guo Ren <guoren@...nel.org>
> diff --git a/drivers/firmware/Kconfig b/drivers/firmware/Kconfig
> index aadc395ee168..fe72e705067c 100644
> --- a/drivers/firmware/Kconfig
> +++ b/drivers/firmware/Kconfig
> @@ -278,6 +278,7 @@ source "drivers/firmware/meson/Kconfig"
>  source "drivers/firmware/microchip/Kconfig"
>  source "drivers/firmware/psci/Kconfig"
>  source "drivers/firmware/qcom/Kconfig"
> +source "drivers/firmware/riscv/Kconfig"
>  source "drivers/firmware/samsung/Kconfig"
>  source "drivers/firmware/smccc/Kconfig"
>  source "drivers/firmware/tegra/Kconfig"
> diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
> index 4ddec2820c96..6cdd84570ea7 100644
> --- a/drivers/firmware/Makefile
> +++ b/drivers/firmware/Makefile
> @@ -34,6 +34,7 @@ obj-y				+= efi/
>  obj-y				+= imx/
>  obj-y				+= psci/
>  obj-y				+= qcom/
> +obj-y				+= riscv/
>  obj-y				+= samsung/
>  obj-y				+= smccc/
>  obj-y				+= tegra/
> diff --git a/drivers/firmware/riscv/Kconfig b/drivers/firmware/riscv/Kconfig
> new file mode 100644
> index 000000000000..8056ed3262d9
> --- /dev/null
> +++ b/drivers/firmware/riscv/Kconfig
> @@ -0,0 +1,15 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +menu "Risc-V Specific firmware drivers"
> +depends on RISCV
> +
> +config RISCV_SSE
> +	bool "Enable SBI Supervisor Software Events support"
> +	depends on RISCV_SBI
> +	default y
> +	help
> +	  The Supervisor Software Events support allow the SBI to deliver
> +	  NMI-like notifications to the supervisor mode software. When enable,
> +	  this option provides support to register callbacks on specific SSE
> +	  events.
> +
> +endmenu
> diff --git a/drivers/firmware/riscv/Makefile b/drivers/firmware/riscv/Makefile
> new file mode 100644
> index 000000000000..4ccfcbbc28ea
> --- /dev/null
> +++ b/drivers/firmware/riscv/Makefile
> @@ -0,0 +1,3 @@
> +# SPDX-License-Identifier: GPL-2.0
> +
> +obj-$(CONFIG_RISCV_SSE)		+= riscv_sse.o
> diff --git a/drivers/firmware/riscv/riscv_sse.c b/drivers/firmware/riscv/riscv_sse.c
> new file mode 100644
> index 000000000000..05e4bc8dfa99
> --- /dev/null
> +++ b/drivers/firmware/riscv/riscv_sse.c
> @@ -0,0 +1,696 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2024 Rivos Inc.
> + */
> +
> +#define pr_fmt(fmt) "sse: " fmt
> +
> +#include <linux/cpu.h>
> +#include <linux/cpuhotplug.h>
> +#include <linux/cpu_pm.h>
> +#include <linux/hardirq.h>
> +#include <linux/list.h>
> +#include <linux/percpu-defs.h>
> +#include <linux/reboot.h>
> +#include <linux/riscv_sse.h>
> +#include <linux/slab.h>
> +
> +#include <asm/sbi.h>
> +#include <asm/sse.h>
> +
> +struct sse_event {
> +	struct list_head list;
> +	u32 evt_id;
> +	u32 priority;
> +	sse_event_handler *handler;
> +	void *handler_arg;
> +	/* Only valid for global events */
> +	unsigned int cpu;
> +
> +	union {
> +		struct sse_registered_event *global;
> +		struct sse_registered_event __percpu *local;
> +	};
> +};
> +
> +static int sse_hp_state;
> +static bool sse_available;

__read_mostly candidates?

> +static DEFINE_SPINLOCK(events_list_lock);
> +static LIST_HEAD(events);
> +static DEFINE_MUTEX(sse_mutex);
> +
> +struct sse_registered_event {
> +	struct sse_event_arch_data arch;
> +	struct sse_event *event;
> +	unsigned long attr_buf;
> +	bool is_enabled;
> +};
> +
> +void sse_handle_event(struct sse_event_arch_data *arch_event,
> +		      struct pt_regs *regs)
> +{
> +	int ret;
> +	struct sse_registered_event *reg_evt =
> +		container_of(arch_event, struct sse_registered_event, arch);
> +	struct sse_event *evt = reg_evt->event;
> +
> +	ret = evt->handler(evt->evt_id, evt->handler_arg, regs);
> +	if (ret)
> +		pr_warn("event %x handler failed with error %d\n", evt->evt_id,
> +			ret);

Nit: Candidate for 100 chars

> +}
> +
> +static struct sse_event *sse_event_get(u32 evt)
> +{
> +	struct sse_event *event = NULL, *tmp;
> +
> +	scoped_guard(spinlock, &events_list_lock) {
> +		list_for_each_entry(tmp, &events, list) {
> +			if (tmp->evt_id == evt)
> +				return event;
> +		}
> +	}
> +
> +	return NULL;
> +}
> +
> +static phys_addr_t sse_event_get_phys(struct sse_registered_event *reg_evt,
> +				      void *addr)
> +{
> +	phys_addr_t phys;
> +
> +	if (sse_event_is_global(reg_evt->event->evt_id))
> +		phys = virt_to_phys(addr);
> +	else
> +		phys = per_cpu_ptr_to_phys(addr);
> +
> +	return phys;
> +}
> +
> +static struct sse_registered_event *sse_get_reg_evt(struct sse_event *event)
> +{
> +	if (sse_event_is_global(event->evt_id))
> +		return event->global;
> +	else
> +		return per_cpu_ptr(event->local, smp_processor_id());
> +}
> +
> +static int sse_sbi_event_func(struct sse_event *event, unsigned long func)
> +{
> +	struct sbiret ret;
> +	u32 evt = event->evt_id;
> +	struct sse_registered_event *reg_evt = sse_get_reg_evt(event);
> +
> +	ret = sbi_ecall(SBI_EXT_SSE, func, evt, 0, 0, 0, 0, 0);
> +	if (ret.error)
> +		pr_debug("Failed to execute func %lx, event %x, error %ld\n",
> +			 func, evt, ret.error);
> +

Would probably fit in 100 chars! Is pr_debug() correct here? Seems more important!

> +	if (func == SBI_SSE_EVENT_DISABLE)
> +		reg_evt->is_enabled = false;
> +	else if (func == SBI_SSE_EVENT_ENABLE)
> +		reg_evt->is_enabled = true;
> +

Hmm, the event is updated, even if the call fail?

> +	return sbi_err_map_linux_errno(ret.error);
> +}
> +
> +int sse_event_disable_local(struct sse_event *event)
> +{
> +	return sse_sbi_event_func(event, SBI_SSE_EVENT_DISABLE);
> +}
> +
> +int sse_event_enable_local(struct sse_event *event)
> +{
> +	return sse_sbi_event_func(event, SBI_SSE_EVENT_ENABLE);
> +}
> +
> +static int sse_event_attr_get_no_lock(struct sse_registered_event *reg_evt,

It's "nolock" everywhere except here!

> +				      unsigned long attr_id, unsigned long *val)
> +{
> +	struct sbiret sret;
> +	u32 evt = reg_evt->event->evt_id;
> +	unsigned long phys;
> +
> +	phys = sse_event_get_phys(reg_evt, &reg_evt->attr_buf);

Seems like the sse_event_get_phys() could get a better name, and only
have the reg_evt passed? This is just getting the PA of the attr Also,
attr_buf? Why buf?

> +
> +	sret = sbi_ecall(SBI_EXT_SSE, SBI_SSE_EVENT_ATTR_READ, evt,
> +				     attr_id, 1, phys, 0, 0);
> +	if (sret.error) {
> +		pr_debug("Failed to get event %x attr %lx, error %ld\n", evt,
> +			 attr_id, sret.error);

Same Q on pr_debug() vs pr_warn().

> +		return sbi_err_map_linux_errno(sret.error);
> +	}
> +
> +	*val = reg_evt->attr_buf;
> +
> +	return 0;
> +}
> +
> +static int sse_event_attr_set_nolock(struct sse_registered_event *reg_evt,
> +				     unsigned long attr_id, unsigned long val)
> +{
> +	struct sbiret sret;
> +	u32 evt = reg_evt->event->evt_id;
> +	unsigned long phys;
> +
> +	reg_evt->attr_buf = val;
> +	phys = sse_event_get_phys(reg_evt, &reg_evt->attr_buf);
> +
> +	sret = sbi_ecall(SBI_EXT_SSE, SBI_SSE_EVENT_ATTR_WRITE, evt,
> +				     attr_id, 1, phys, 0, 0);
> +	if (sret.error) {
> +		pr_debug("Failed to set event %x attr %lx, error %ld\n", evt,
> +			 attr_id, sret.error);

Dito.

> +		return sbi_err_map_linux_errno(sret.error);

Can be remove out of the if-statement, and remove "return 0".

> +	}
> +
> +	return 0;
> +}
> +
> +static int sse_event_set_target_cpu_nolock(struct sse_event *event,
> +					   unsigned int cpu)
> +{
> +	unsigned int hart_id = cpuid_to_hartid_map(cpu);
> +	struct sse_registered_event *reg_evt = event->global;
> +	u32 evt = event->evt_id;
> +	bool was_enabled;
> +	int ret;
> +
> +	if (!sse_event_is_global(evt))
> +		return -EINVAL;
> +
> +	was_enabled = reg_evt->is_enabled;
> +	if (was_enabled)
> +		sse_event_disable_local(event);
> +	do {
> +		ret = sse_event_attr_set_nolock(reg_evt,
> +						SBI_SSE_ATTR_PREFERRED_HART,
> +						hart_id);
> +	} while (ret == -EINVAL);

Please explain the while-loop rationale! Scary!

> +
> +	if (ret == 0)
> +		event->cpu = cpu;
> +
> +	if (was_enabled)
> +		sse_event_enable_local(event);
> +
> +	return 0;
> +}
> +
> +int sse_event_set_target_cpu(struct sse_event *event, unsigned int cpu)
> +{
> +	int ret;
> +
> +	scoped_guard(mutex, &sse_mutex) {
> +		cpus_read_lock();
> +
> +		if (!cpu_online(cpu))
> +			return -EINVAL;

cpus_read_unlock() missing! If only there was some way of having a
scoped guard! ;-P Hint: guard(cpus_read_lock)(); and clean up the return
path.

> +
> +		ret = sse_event_set_target_cpu_nolock(event, cpu);
> +
> +		cpus_read_unlock();
> +	}
> +
> +	return ret;
> +}
> +
> +static int sse_event_init_registered(unsigned int cpu,
> +				     struct sse_registered_event *reg_evt,
> +				     struct sse_event *event)
> +{
> +	reg_evt->event = event;
> +	arch_sse_init_event(&reg_evt->arch, event->evt_id, cpu);

This function can fail!

> +
> +	return 0;
> +}
> +
> +static void sse_event_free_registered(struct sse_registered_event *reg_evt)
> +{
> +	arch_sse_free_event(&reg_evt->arch);
> +}
> +
> +static int sse_event_alloc_global(struct sse_event *event)
> +{
> +	int err;
> +	struct sse_registered_event *reg_evt;
> +
> +	reg_evt = kzalloc(sizeof(*reg_evt), GFP_KERNEL);
> +	if (!reg_evt)
> +		return -ENOMEM;
> +
> +	event->global = reg_evt;
> +	err = sse_event_init_registered(smp_processor_id(), reg_evt, event);
> +	if (err)
> +		kfree(reg_evt);
> +
> +	return err;
> +}
> +
> +static int sse_event_alloc_local(struct sse_event *event)
> +{
> +	int err;
> +	unsigned int cpu, err_cpu;
> +	struct sse_registered_event *reg_evt;
> +	struct sse_registered_event __percpu *reg_evts;
> +
> +	reg_evts = alloc_percpu(struct sse_registered_event);
> +	if (!reg_evts)
> +		return -ENOMEM;
> +
> +	event->local = reg_evts;
> +
> +	for_each_possible_cpu(cpu) {
> +		reg_evt = per_cpu_ptr(reg_evts, cpu);
> +		err = sse_event_init_registered(cpu, reg_evt, event);
> +		if (err) {
> +			err_cpu = cpu;
> +			goto err_free_per_cpu;
> +		}
> +	}
> +
> +	return 0;
> +
> +err_free_per_cpu:
> +	for_each_possible_cpu(cpu) {
> +		if (cpu == err_cpu)
> +			break;
> +		reg_evt = per_cpu_ptr(reg_evts, cpu);
> +		sse_event_free_registered(reg_evt);
> +	}
> +
> +	free_percpu(reg_evts);
> +
> +	return err;
> +}
> +
> +static struct sse_event *sse_event_alloc(u32 evt, u32 priority,
> +					 sse_event_handler *handler, void *arg)
> +{
> +	int err;
> +	struct sse_event *event;
> +
> +	event = kzalloc(sizeof(*event), GFP_KERNEL);
> +	if (!event)
> +		return ERR_PTR(-ENOMEM);
> +
> +	event->evt_id = evt;
> +	event->priority = priority;
> +	event->handler_arg = arg;
> +	event->handler = handler;
> +
> +	if (sse_event_is_global(evt)) {
> +		err = sse_event_alloc_global(event);
> +		if (err)
> +			goto err_alloc_reg_evt;
> +	} else {
> +		err = sse_event_alloc_local(event);
> +		if (err)
> +			goto err_alloc_reg_evt;

Move the if (err) clause out -- simplify.

> +	}
> +
> +	return event;
> +
> +err_alloc_reg_evt:
> +	kfree(event);
> +
> +	return ERR_PTR(err);
> +}
> +
> +static int sse_sbi_register_event(struct sse_event *event,
> +				  struct sse_registered_event *reg_evt)
> +{
> +	int ret;
> +
> +	ret = sse_event_attr_set_nolock(reg_evt, SBI_SSE_ATTR_PRIO,
> +					event->priority);
> +	if (ret)
> +		return ret;
> +
> +	return arch_sse_register_event(&reg_evt->arch);
> +}
> +
> +static int sse_event_register_local(struct sse_event *event)
> +{
> +	int ret;

Add space.

> +	struct sse_registered_event *reg_evt = per_cpu_ptr(event->local,
> +							   smp_processor_id());
> +
> +	ret = sse_sbi_register_event(event, reg_evt);
> +	if (ret)
> +		pr_debug("Failed to register event %x: err %d\n", event->evt_id,
> +			 ret);
> +
> +	return ret;
> +}
> +
> +static int sse_sbi_unregister_event(struct sse_event *event)
> +{
> +	return sse_sbi_event_func(event, SBI_SSE_EVENT_UNREGISTER);
> +}
> +
> +struct sse_per_cpu_evt {
> +	struct sse_event *event;
> +	unsigned long func;
> +	atomic_t error;
> +};
> +
> +static void sse_event_per_cpu_func(void *info)
> +{
> +	int ret;
> +	struct sse_per_cpu_evt *cpu_evt = info;
> +
> +	if (cpu_evt->func == SBI_SSE_EVENT_REGISTER)
> +		ret = sse_event_register_local(cpu_evt->event);
> +	else
> +		ret = sse_sbi_event_func(cpu_evt->event, cpu_evt->func);
> +
> +	if (ret)
> +		atomic_set(&cpu_evt->error, ret);
> +}
> +
> +static void sse_event_free(struct sse_event *event)
> +{
> +	unsigned int cpu;
> +	struct sse_registered_event *reg_evt;
> +
> +	if (sse_event_is_global(event->evt_id)) {
> +		sse_event_free_registered(event->global);
> +		kfree(event->global);
> +	} else {
> +		for_each_possible_cpu(cpu) {
> +			reg_evt = per_cpu_ptr(event->local, cpu);
> +			sse_event_free_registered(reg_evt);
> +		}
> +		free_percpu(event->local);
> +	}
> +
> +	kfree(event);
> +}
> +
> +int sse_event_enable(struct sse_event *event)
> +{
> +	int ret = 0, cpu;
> +	struct sse_per_cpu_evt cpu_evt;
> +	struct sse_registered_event *reg_evt;
> +
> +	scoped_guard(mutex, &sse_mutex) {
> +		cpus_read_lock();
> +		if (sse_event_is_global(event->evt_id)) {
> +			reg_evt = event->global;
> +			ret = sse_event_enable_local(event);
> +		} else {
> +			cpu_evt.event = event;
> +			atomic_set(&cpu_evt.error, 0);
> +			cpu_evt.func = SBI_SSE_EVENT_ENABLE;
> +			on_each_cpu(sse_event_per_cpu_func, &cpu_evt, 1);
> +			ret = atomic_read(&cpu_evt.error);
> +			if (ret) {
> +				cpu_evt.func = SBI_SSE_EVENT_DISABLE;
> +				on_each_cpu(sse_event_per_cpu_func, &cpu_evt, 1);
> +			} else {
> +				for_each_online_cpu(cpu) {

Something missing?

Also, use guard() to simplify this!

> +
> +				}
> +			}
> +		}
> +		cpus_read_unlock();
> +	}
> +
> +	return ret;
> +}
> +
> +static void sse_events_mask(void)
> +{
> +	sbi_ecall(SBI_EXT_SSE, SBI_SSE_EVENT_HART_MASK, 0, 0, 0, 0, 0, 0);

Return value?

> +}
> +
> +static void sse_events_unmask(void)
> +{
> +	sbi_ecall(SBI_EXT_SSE, SBI_SSE_EVENT_HART_UNMASK, 0, 0, 0, 0, 0, 0);
> +}
> +
> +static void sse_event_disable_nolock(struct sse_event *event)
> +{
> +	struct sse_per_cpu_evt cpu_evt;
> +
> +	if (sse_event_is_global(event->evt_id)) {
> +		sse_event_disable_local(event);
> +	} else {
> +		cpu_evt.event = event;
> +		cpu_evt.func = SBI_SSE_EVENT_DISABLE;
> +		on_each_cpu(sse_event_per_cpu_func, &cpu_evt, 1);
> +	}
> +}
> +
> +void sse_event_disable(struct sse_event *event)
> +{
> +	scoped_guard(mutex, &sse_mutex) {
> +		cpus_read_lock();
> +		sse_event_disable_nolock(event);
> +		cpus_read_unlock();
> +	}
> +}
> +
> +struct sse_event *sse_event_register(u32 evt, u32 priority,
> +				     sse_event_handler *handler, void *arg)
> +{
> +	struct sse_per_cpu_evt cpu_evt;
> +	struct sse_event *event;
> +	int ret = 0;
> +
> +	if (!sse_available)
> +		return ERR_PTR(-EOPNOTSUPP);
> +
> +	mutex_lock(&sse_mutex);
> +	if (sse_event_get(evt)) {
> +		pr_debug("Event %x already registered\n", evt);
> +		ret = -EEXIST;
> +		goto out_unlock;
> +	}
> +
> +	event = sse_event_alloc(evt, priority, handler, arg);
> +	if (IS_ERR(event)) {
> +		ret = PTR_ERR(event);
> +		goto out_unlock;
> +	}
> +
> +	cpus_read_lock();
> +	if (sse_event_is_global(evt)) {
> +		unsigned long preferred_hart;
> +
> +		ret = sse_event_attr_get_no_lock(event->global,
> +						 SBI_SSE_ATTR_PREFERRED_HART,
> +						 &preferred_hart);
> +		if (ret)
> +			goto err_event_free;
> +		event->cpu = riscv_hartid_to_cpuid(preferred_hart);
> +
> +		ret = sse_sbi_register_event(event, event->global);
> +		if (ret)
> +			goto err_event_free;
> +
> +	} else {
> +		cpu_evt.event = event;
> +		atomic_set(&cpu_evt.error, 0);
> +		cpu_evt.func = SBI_SSE_EVENT_REGISTER;
> +		on_each_cpu(sse_event_per_cpu_func, &cpu_evt, 1);
> +		ret = atomic_read(&cpu_evt.error);
> +		if (ret) {
> +			cpu_evt.func = SBI_SSE_EVENT_UNREGISTER;
> +			on_each_cpu(sse_event_per_cpu_func, &cpu_evt, 1);
> +			goto err_event_free;
> +		}
> +	}
> +	cpus_read_unlock();
> +
> +	scoped_guard(spinlock, &events_list_lock)
> +		list_add(&event->list, &events);
> +
> +	mutex_unlock(&sse_mutex);
> +
> +	return event;
> +
> +err_event_free:
> +	cpus_read_unlock();
> +	sse_event_free(event);
> +out_unlock:
> +	mutex_unlock(&sse_mutex);
> +
> +	return ERR_PTR(ret);
> +}
> +
> +static void sse_event_unregister_nolock(struct sse_event *event)
> +{
> +	struct sse_per_cpu_evt cpu_evt;
> +
> +	if (sse_event_is_global(event->evt_id)) {
> +		sse_sbi_unregister_event(event);
> +	} else {
> +		cpu_evt.event = event;
> +		cpu_evt.func = SBI_SSE_EVENT_UNREGISTER;
> +		on_each_cpu(sse_event_per_cpu_func, &cpu_evt, 1);
> +	}
> +}
> +
> +void sse_event_unregister(struct sse_event *event)
> +{
> +	scoped_guard(mutex, &sse_mutex) {
> +		cpus_read_lock();
> +		sse_event_unregister_nolock(event);
> +		cpus_read_unlock();
> +
> +		scoped_guard(spinlock, &events_list_lock)
> +			list_del(&event->list);
> +
> +		sse_event_free(event);
> +	}
> +}
> +
> +static int sse_cpu_online(unsigned int cpu)
> +{
> +	struct sse_event *event;
> +
> +	scoped_guard(spinlock, &events_list_lock) {
> +		list_for_each_entry(event, &events, list) {
> +			if (sse_event_is_global(event->evt_id))
> +				continue;
> +
> +			sse_event_register_local(event);
> +			if (sse_get_reg_evt(event))
> +				sse_event_enable_local(event);
> +		}
> +	}
> +
> +	/* Ready to handle events. Unmask SSE. */
> +	sse_events_unmask();
> +
> +	return 0;
> +}
> +
> +static int sse_cpu_teardown(unsigned int cpu)
> +{
> +	unsigned int next_cpu;
> +	struct sse_event *event;
> +
> +	/* Mask the sse events */
> +	sse_events_mask();
> +
> +	scoped_guard(spinlock, &events_list_lock) {
> +		list_for_each_entry(event, &events, list) {
> +			if (!sse_event_is_global(event->evt_id)) {
> +
> +				if (event->global->is_enabled)
> +					sse_event_disable_local(event);
> +
> +				sse_sbi_unregister_event(event);
> +				continue;
> +			}
> +
> +			if (event->cpu != smp_processor_id())
> +				continue;
> +
> +			/* Update destination hart for global event */
> +			next_cpu = cpumask_any_but(cpu_online_mask, cpu);
> +			sse_event_set_target_cpu_nolock(event, next_cpu);
> +		}
> +	}
> +
> +	return 0;
> +}
> +
> +static void sse_reset(void)
> +{
> +	struct sse_event *event = NULL;

No need for init here.



Björn

> +
> +	list_for_each_entry(event, &events, list) {
> +		sse_event_disable_nolock(event);
> +		sse_event_unregister_nolock(event);
> +	}
> +}
> +
> +static int sse_pm_notifier(struct notifier_block *nb, unsigned long action,
> +			   void *data)
> +{
> +	WARN_ON_ONCE(preemptible());
> +
> +	switch (action) {
> +	case CPU_PM_ENTER:
> +		sse_events_mask();
> +		break;
> +	case CPU_PM_EXIT:
> +	case CPU_PM_ENTER_FAILED:
> +		sse_events_unmask();
> +		break;
> +	default:
> +		return NOTIFY_DONE;
> +	}
> +
> +	return NOTIFY_OK;
> +}
> +
> +static struct notifier_block sse_pm_nb = {
> +	.notifier_call = sse_pm_notifier,
> +};
> +
> +/*
> + * Mask all CPUs and unregister all events on panic, reboot or kexec.
> + */
> +static int sse_reboot_notifier(struct notifier_block *nb, unsigned long action,
> +				void *data)
> +{
> +	cpuhp_remove_state(sse_hp_state);
> +
> +	sse_reset();
> +
> +	return NOTIFY_OK;
> +}
> +
> +static struct notifier_block sse_reboot_nb = {
> +	.notifier_call = sse_reboot_notifier,
> +};
> +
> +static int __init sse_init(void)
> +{
> +	int cpu, ret;
> +
> +	if (sbi_probe_extension(SBI_EXT_SSE) <= 0) {
> +		pr_err("Missing SBI SSE extension\n");
> +		return -EOPNOTSUPP;
> +	}
> +	pr_info("SBI SSE extension detected\n");
> +
> +	for_each_possible_cpu(cpu)
> +		INIT_LIST_HEAD(&events);
> +
> +	ret = cpu_pm_register_notifier(&sse_pm_nb);
> +	if (ret) {
> +		pr_warn("Failed to register CPU PM notifier...\n");
> +		return ret;
> +	}
> +
> +	ret = register_reboot_notifier(&sse_reboot_nb);
> +	if (ret) {
> +		pr_warn("Failed to register reboot notifier...\n");
> +		goto remove_cpupm;
> +	}
> +
> +	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "riscv/sse:online",
> +				sse_cpu_online, sse_cpu_teardown);
> +	if (ret < 0)
> +		goto remove_reboot;
> +
> +	sse_hp_state = ret;
> +	sse_available = true;
> +
> +	return 0;
> +
> +remove_reboot:
> +	unregister_reboot_notifier(&sse_reboot_nb);
> +
> +remove_cpupm:
> +	cpu_pm_unregister_notifier(&sse_pm_nb);
> +
> +	return ret;
> +}
> +arch_initcall(sse_init);
> diff --git a/include/linux/riscv_sse.h b/include/linux/riscv_sse.h
> new file mode 100644
> index 000000000000..8653fa74ec82
> --- /dev/null
> +++ b/include/linux/riscv_sse.h
> @@ -0,0 +1,59 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * Copyright (C) 2024 Rivos Inc.
> + */
> +
> +#ifndef __LINUX_RISCV_SSE_H
> +#define __LINUX_RISCV_SSE_H
> +
> +#include <linux/types.h>
> +#include <linux/linkage.h>
> +
> +struct sse_event;
> +struct pt_regs;
> +
> +typedef int (sse_event_handler)(u32 event_num, void *arg, struct pt_regs *regs);
> +
> +#ifdef CONFIG_RISCV_SSE
> +
> +struct sse_event *sse_event_register(u32 event_num, u32 priority,
> +				     sse_event_handler *handler, void *arg);
> +
> +void sse_event_unregister(struct sse_event *evt);
> +
> +int sse_event_set_target_cpu(struct sse_event *sse_evt, unsigned int cpu);
> +
> +int sse_event_enable(struct sse_event *sse_evt);
> +
> +void sse_event_disable(struct sse_event *sse_evt);
> +
> +int sse_event_enable_local(struct sse_event *sse_evt);
> +int sse_event_disable_local(struct sse_event *sse_evt);
> +
> +#else
> +static inline struct sse_event *sse_event_register(u32 event_num, u32 priority,
> +						   sse_event_handler *handler,
> +						   void *arg)
> +{
> +	return ERR_PTR(-EOPNOTSUPP);
> +}
> +
> +static inline void sse_event_unregister(struct sse_event *evt) {}
> +
> +static inline int sse_event_set_target_cpu(struct sse_event *sse_evt,
> +					   unsigned int cpu)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static inline int sse_event_enable(struct sse_event *sse_evt)
> +{
> +	return -EOPNOTSUPP;
> +}
> +
> +static inline void sse_event_disable(struct sse_event *sse_evt) {}
> +
> +
> +#endif
> +
> +#endif /* __LINUX_RISCV_SSE_H */
> -- 
> 2.49.0
>
>
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