linux-kernel - Re: [PATCH v6 1/5] riscv: add SBI SSE extension definitions

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Message-ID: <2a9906d7-c914-4e69-8c72-ac848659650c@rivosinc.com>
Date: Wed, 13 Aug 2025 12:49:17 +0200
From: Clément Léger <cleger@...osinc.com>
To: Alexandre Ghiti <alex@...ti.fr>, 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: Himanshu Chauhan <hchauhan@...tanamicro.com>,
 Anup Patel <apatel@...tanamicro.com>, Xu Lu <luxu.kernel@...edance.com>,
 Atish Patra <atishp@...shpatra.org>, Björn Töpel
 <bjorn@...osinc.com>, Yunhui Cui <cuiyunhui@...edance.com>
Subject: Re: [PATCH v6 1/5] riscv: add SBI SSE extension definitions



On 13/08/2025 11:01, Alexandre Ghiti wrote:
> Hi Clément,
> 
> On 8/8/25 17:38, Clément Léger wrote:
>> Add needed definitions for SBI Supervisor Software Events extension [1].
>> This extension enables the SBI to inject events into supervisor software
>> much like ARM SDEI.
>>
>> [1] https://lists.riscv.org/g/tech-prs/message/515
>>
>> Signed-off-by: Clément Léger <cleger@...osinc.com>
>> ---
>>   arch/riscv/include/asm/sbi.h | 61 ++++++++++++++++++++++++++++++++++++
>>   1 file changed, 61 insertions(+)
>>
>> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
>> index 341e74238aa0..e4993fb664d2 100644
>> --- a/arch/riscv/include/asm/sbi.h
>> +++ b/arch/riscv/include/asm/sbi.h
>> @@ -36,6 +36,7 @@ enum sbi_ext_id {
>>       SBI_EXT_STA = 0x535441,
>>       SBI_EXT_NACL = 0x4E41434C,
>>       SBI_EXT_FWFT = 0x46574654,
>> +    SBI_EXT_SSE = 0x535345,
>>         /* Experimentals extensions must lie within this range */
>>       SBI_EXT_EXPERIMENTAL_START = 0x08000000,
>> @@ -430,6 +431,66 @@ enum sbi_fwft_feature_t {
>>     #define SBI_FWFT_SET_FLAG_LOCK            BIT(0)
>>   +enum sbi_ext_sse_fid {
>> +    SBI_SSE_EVENT_ATTR_READ = 0,
>> +    SBI_SSE_EVENT_ATTR_WRITE,
>> +    SBI_SSE_EVENT_REGISTER,
>> +    SBI_SSE_EVENT_UNREGISTER,
>> +    SBI_SSE_EVENT_ENABLE,
>> +    SBI_SSE_EVENT_DISABLE,
>> +    SBI_SSE_EVENT_COMPLETE,
>> +    SBI_SSE_EVENT_SIGNAL,
> 
> 
> Nit but in the specification this event is referred as "inject" instead
> of "signal", any reason to change that naming?

Hi Alex,

That's mostly for historic reason, spec changed that after a few
revision. I'll update that.

Thanks,

Clément
> 
> 
>> +    SBI_SSE_EVENT_HART_UNMASK,
>> +    SBI_SSE_EVENT_HART_MASK,
>> +};
>> +
>> +enum sbi_sse_state {
>> +    SBI_SSE_STATE_UNUSED     = 0,
>> +    SBI_SSE_STATE_REGISTERED = 1,
>> +    SBI_SSE_STATE_ENABLED    = 2,
>> +    SBI_SSE_STATE_RUNNING    = 3,
>> +};
>> +
>> +/* SBI SSE Event Attributes. */
>> +enum sbi_sse_attr_id {
>> +    SBI_SSE_ATTR_STATUS        = 0x00000000,
>> +    SBI_SSE_ATTR_PRIO        = 0x00000001,
>> +    SBI_SSE_ATTR_CONFIG        = 0x00000002,
>> +    SBI_SSE_ATTR_PREFERRED_HART    = 0x00000003,
>> +    SBI_SSE_ATTR_ENTRY_PC        = 0x00000004,
>> +    SBI_SSE_ATTR_ENTRY_ARG        = 0x00000005,
>> +    SBI_SSE_ATTR_INTERRUPTED_SEPC    = 0x00000006,
>> +    SBI_SSE_ATTR_INTERRUPTED_FLAGS    = 0x00000007,
>> +    SBI_SSE_ATTR_INTERRUPTED_A6    = 0x00000008,
>> +    SBI_SSE_ATTR_INTERRUPTED_A7    = 0x00000009,
>> +
>> +    SBI_SSE_ATTR_MAX        = 0x0000000A
>> +};
>> +
>> +#define SBI_SSE_ATTR_STATUS_STATE_OFFSET    0
>> +#define SBI_SSE_ATTR_STATUS_STATE_MASK        0x3
>> +#define SBI_SSE_ATTR_STATUS_PENDING_OFFSET    2
>> +#define SBI_SSE_ATTR_STATUS_INJECT_OFFSET    3
>> +
>> +#define SBI_SSE_ATTR_CONFIG_ONESHOT    BIT(0)
>> +
>> +#define SBI_SSE_ATTR_INTERRUPTED_FLAGS_SSTATUS_SPP    BIT(0)
>> +#define SBI_SSE_ATTR_INTERRUPTED_FLAGS_SSTATUS_SPIE    BIT(1)
>> +#define SBI_SSE_ATTR_INTERRUPTED_FLAGS_HSTATUS_SPV    BIT(2)
>> +#define SBI_SSE_ATTR_INTERRUPTED_FLAGS_HSTATUS_SPVP    BIT(3)
>> +
>> +#define SBI_SSE_EVENT_LOCAL_HIGH_PRIO_RAS    0x00000000
>> +#define SBI_SSE_EVENT_LOCAL_DOUBLE_TRAP        0x00000001
>> +#define SBI_SSE_EVENT_GLOBAL_HIGH_PRIO_RAS    0x00008000
>> +#define SBI_SSE_EVENT_LOCAL_PMU_OVERFLOW    0x00010000
>> +#define SBI_SSE_EVENT_LOCAL_LOW_PRIO_RAS    0x00100000
>> +#define SBI_SSE_EVENT_GLOBAL_LOW_PRIO_RAS    0x00108000
>> +#define SBI_SSE_EVENT_LOCAL_SOFTWARE_INJECTED    0xffff0000
>> +#define SBI_SSE_EVENT_GLOBAL_SOFTWARE_INJECTED    0xffff8000
> 
> 
> And here you use "injected".
> 
> 
>> +
>> +#define SBI_SSE_EVENT_PLATFORM        BIT(14)
>> +#define SBI_SSE_EVENT_GLOBAL        BIT(15)
>> +
>>   /* SBI spec version fields */
>>   #define SBI_SPEC_VERSION_DEFAULT    0x1
>>   #define SBI_SPEC_VERSION_MAJOR_SHIFT    24