Message-ID: <20250116-boxy-handoff-2f2790b5388e@spud>
Date: Thu, 16 Jan 2025 13:58:29 +0000
From: Conor Dooley <conor@...nel.org>
To: Clément Léger <cleger@...osinc.com>
Cc: 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,
	Himanshu Chauhan <hchauhan@...tanamicro.com>,
	Anup Patel <apatel@...tanamicro.com>,
	Xu Lu <luxu.kernel@...edance.com>,
	Atish Patra <atishp@...shpatra.org>
Subject: Re: [PATCH v3 3/4] drivers: firmware: add riscv SSE support

On Fri, Dec 06, 2024 at 05:30:59PM +0100, Clément Léger wrote:
> 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>
> ---
>  MAINTAINERS                        |  14 +
>  drivers/firmware/Kconfig           |   1 +
>  drivers/firmware/Makefile          |   1 +
>  drivers/firmware/riscv/Kconfig     |  15 +
>  drivers/firmware/riscv/Makefile    |   3 +
>  drivers/firmware/riscv/riscv_sse.c | 691 +++++++++++++++++++++++++++++
>  include/linux/riscv_sse.h          |  56 +++
>  7 files changed, 781 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 686109008d8e..a3ddde7fe9fb 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -20125,6 +20125,13 @@ 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/*

Acked-by: Conor Dooley <conor.dooley@...rochip.com>

(got some, mostly minor, comments below)

> 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..c165e32cc9a5
> --- /dev/null
> +++ b/drivers/firmware/riscv/riscv_sse.c
> @@ -0,0 +1,691 @@
> +// 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;
> +	u32 priority;
> +	sse_event_handler *handler;
> +	void *handler_arg;
> +	bool is_enabled;
> +	/* 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;
> +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 *evt;
> +	unsigned long attr_buf;
> +};
> +
> +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->evt;
> +
> +	ret = evt->handler(evt->evt, evt->handler_arg, regs);

Is it possible to get here with a null handler? Or will !registered
events not lead to the handler getting called?

> +	if (ret)
> +		pr_warn("event %x handler failed with error %d\n", evt->evt,
> +			ret);
> +}
> +
> +static bool sse_event_is_global(u32 evt)
> +{
> +	return !!(evt & SBI_SSE_EVENT_GLOBAL);
> +}
> +
> +static
> +struct sse_event *sse_event_get(u32 evt)

nit: Could you shift this into one line?

> +{
> +	struct sse_event *sse_evt = NULL, *tmp;
> +
> +	scoped_guard(spinlock, &events_list_lock) {
> +		list_for_each_entry(tmp, &events, list) {
> +			if (tmp->evt == evt) {
> +				return sse_evt;
> +			}
> +		}
> +	}
> +
> +	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->evt->evt))
> +		phys = virt_to_phys(addr);
> +	else
> +		phys = per_cpu_ptr_to_phys(addr);
> +
> +	return phys;
> +}
> +
> +static int sse_sbi_event_func(struct sse_event *event, unsigned long func)
> +{
> +	struct sbiret ret;
> +	u32 evt = event->evt;
> +
> +	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);

Why's this only at a debug level?

> +
> +	return sbi_err_map_linux_errno(ret.error);
> +}
> +
> +static int sse_sbi_disable_event(struct sse_event *event)
> +{
> +	return sse_sbi_event_func(event, SBI_SSE_EVENT_DISABLE);
> +}
> +
> +static int sse_sbi_enable_event(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,
> +				      unsigned long attr_id, unsigned long *val)
> +{
> +	struct sbiret sret;
> +	u32 evt = reg_evt->evt->evt;
> +	unsigned long phys;
> +
> +	phys = sse_event_get_phys(reg_evt, &reg_evt->attr_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);
> +		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->evt->evt;
> +	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 && sret.error != SBI_ERR_INVALID_STATE) {

Why's the invalid state error not treated as an error?

> +		pr_debug("Failed to set event %x attr %lx, error %ld\n", evt,
> +			 attr_id, sret.error);
> +		return sbi_err_map_linux_errno(sret.error);
> +	}
> +
> +	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;
> +	bool was_enabled;
> +	int ret;
> +
> +	if (!sse_event_is_global(evt))
> +		return -EINVAL;
> +
> +	was_enabled = event->is_enabled;
> +	if (was_enabled)
> +		sse_sbi_disable_event(event);
> +	do {
> +		ret = sse_event_attr_set_nolock(reg_evt,
> +						SBI_SSE_ATTR_PREFERRED_HART,
> +						hart_id);
> +	} while (ret == -EINVAL);
> +
> +	if (ret == 0)
> +		event->cpu = cpu;
> +
> +	if (was_enabled)
> +		sse_sbi_enable_event(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;
> +
> +		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->evt = event;
> +	arch_sse_init_event(&reg_evt->arch, event->evt, cpu);
> +
> +	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 = 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;
> +	}
> +
> +	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;
> +	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,
> +			 ret);

Same here I guess, why's a registration failure only a debug print?

> +
> +	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)) {
> +		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;
> +	struct sse_per_cpu_evt cpu_evt;
> +
> +	scoped_guard(mutex, &sse_mutex) {
> +		cpus_read_lock();
> +		if (sse_event_is_global(event->evt)) {
> +			ret = sse_sbi_enable_event(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);

nit: this should fit on one line, no?

> +			}
> +		}
> +		cpus_read_unlock();
> +
> +		if (ret == 0)
> +			event->is_enabled = true;
> +	}
> +
> +	return ret;
> +}

> 2.45.2
> 

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