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

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Message-ID: <20250319-46b625cf8b771616d4c7c053@orel>
Date: Wed, 19 Mar 2025 18:08:43 +0100
From: Andrew Jones <ajones@...tanamicro.com>
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 2/4] riscv: add support for SBI Supervisor Software
 Events extension

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.

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,