linux-kernel - Re: [PATCH v3 2/4] riscv: add support for SBI Supervisor Software Events extension

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Message-ID: <b3fbd730-295f-4491-b0d6-d4e258941ae5@rivosinc.com>
Date: Thu, 20 Mar 2025 09:16:07 +0100
From: Clément Léger <cleger@...osinc.com>
To: Andrew Jones <ajones@...tanamicro.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 2/4] riscv: add support for SBI Supervisor Software
 Events extension



On 19/03/2025 18:08, Andrew Jones wrote:
> On Fri, Dec 06, 2024 at 05:30:58PM +0100, Clément Léger wrote:
> ...
>> +int arch_sse_init_event(struct sse_event_arch_data *arch_evt, u32 evt_id, int cpu)
>> +{
>> +	void *stack;
>> +
>> +	arch_evt->evt_id = evt_id;
>> +	stack = sse_stack_alloc(cpu, SSE_STACK_SIZE);
>> +	if (!stack)
>> +		return -ENOMEM;
>> +
>> +	arch_evt->stack = stack + SSE_STACK_SIZE;
>> +
>> +	if (sse_init_scs(cpu, arch_evt))
>> +		goto free_stack;
>> +
>> +	if (is_kernel_percpu_address((unsigned long)&arch_evt->interrupted)) {
>> +		arch_evt->interrupted_state_phys =
>> +				per_cpu_ptr_to_phys(&arch_evt->interrupted);
>> +	} else {
>> +		arch_evt->interrupted_state_phys =
>> +				virt_to_phys(&arch_evt->interrupted);
>> +	}
>> +
>> +	return 0;
> 
> Hi Clément,
> 
> Testing SSE support with tools/testing/selftests/kvm/riscv/sbi_pmu_test
> led to an opensbi sbi_trap_error because the output_phys_lo address passed
> to sbi_sse_read_attrs() wasn't a physical address. The reason is that
> is_kernel_percpu_address() can only be used on static percpu addresses,
> but local sse events get their percpu addresses with alloc_percpu(), so
> is_kernel_percpu_address() was returning false even for local events. I
> made the following changes to get things working.

Hi Andrew,

Did something changed recently ? Because I tested that when it was send
(PMU + some kernel internal testsuite) and didn't saw that. Anyway, I'll
respin it with your changes as well.

Thanks !

Clément

> 
> Thanks,
> drew
> 
> diff --git a/arch/riscv/kernel/sse.c b/arch/riscv/kernel/sse.c
> index b48ae69dad8d..f46893946086 100644
> --- a/arch/riscv/kernel/sse.c
> +++ b/arch/riscv/kernel/sse.c
> @@ -100,12 +100,12 @@ int arch_sse_init_event(struct sse_event_arch_data *arch_evt, u32 evt_id, int cp
>         if (sse_init_scs(cpu, arch_evt))
>                 goto free_stack;
> 
> -       if (is_kernel_percpu_address((unsigned long)&arch_evt->interrupted)) {
> +       if (sse_event_is_global(evt_id)) {
>                 arch_evt->interrupted_state_phys =
> -                               per_cpu_ptr_to_phys(&arch_evt->interrupted);
> +                               virt_to_phys(&arch_evt->interrupted);
>         } else {
>                 arch_evt->interrupted_state_phys =
> -                               virt_to_phys(&arch_evt->interrupted);
> +                               per_cpu_ptr_to_phys(&arch_evt->interrupted);
>         }
> 
>         return 0;
> diff --git a/drivers/firmware/riscv/riscv_sse.c b/drivers/firmware/riscv/riscv_sse.c
> index 511db9ad7a9e..fef375046f75 100644
> --- a/drivers/firmware/riscv/riscv_sse.c
> +++ b/drivers/firmware/riscv/riscv_sse.c
> @@ -62,11 +62,6 @@ void sse_handle_event(struct sse_event_arch_data *arch_event,
>                         ret);
>  }
> 
> -static bool sse_event_is_global(u32 evt)
> -{
> -       return !!(evt & SBI_SSE_EVENT_GLOBAL);
> -}
> -
>  static
>  struct sse_event *sse_event_get(u32 evt)
>  {
> diff --git a/include/linux/riscv_sse.h b/include/linux/riscv_sse.h
> index 16700677f1e8..06b757b036b0 100644
> --- a/include/linux/riscv_sse.h
> +++ b/include/linux/riscv_sse.h
> @@ -8,6 +8,7 @@
> 
>  #include <linux/types.h>
>  #include <linux/linkage.h>
> +#include <asm/sbi.h>
> 
>  struct sse_event;
>  struct pt_regs;
> @@ -16,6 +17,11 @@ struct ghes;
> 
>  typedef int (sse_event_handler)(u32 event_num, void *arg, struct pt_regs *regs);
> 
> +static inline bool sse_event_is_global(u32 evt)
> +{
> +       return !!(evt & SBI_SSE_EVENT_GLOBAL);
> +}
> +
>  #ifdef CONFIG_RISCV_SSE
> 
>  struct sse_event *sse_event_register(u32 event_num, u32 priority,