[PATCH] lib: sbi: Enable Ssqosid Ext using mstateen0

[Anup Patel]

On Tue, Sep 23, 2025 at 3:28 PM <cp0613 at linux.alibaba.com> wrote:
>
> From: Chen Pei <cp0613 at linux.alibaba.com>
>
> The QoS Identifiers extension (Ssqosid) introduces the srmcfg register,
> which configures a hart with two identifiers: a Resource Control ID
> (RCID) and a Monitoring Counter ID (MCID). These identifiers accompany
> each request issued by the hart to shared resource controllers.
>
> If extension Smstateen is implemented together with Ssqosid, then
> Ssqosid also requires the SRMCFG bit in mstateen0 to be implemented. If
> mstateen0.SRMCFG is 0, attempts to access srmcfg in privilege modes less
> privileged than M-mode raise an illegal-instruction exception. If
> mstateen0.SRMCFG is 1 or if extension Smstateen is not implemented,
> attempts to access srmcfg when V=1 raise a virtual-instruction exception.
>
> This extension can be found in the RISC-V Instruction Set Manual:
> https://github.com/riscv/riscv-isa-manual
>
> Signed-off-by: Chen Pei <cp0613 at linux.alibaba.com>
> ---
>  include/sbi/riscv_encoding.h | 5 +++++
>  include/sbi/sbi_hart.h       | 2 ++
>  lib/sbi/sbi_hart.c           | 9 +++++++++
>  3 files changed, 16 insertions(+)
>
> diff --git a/include/sbi/riscv_encoding.h b/include/sbi/riscv_encoding.h
> index 40a854e..88d23b9 100644
> --- a/include/sbi/riscv_encoding.h
> +++ b/include/sbi/riscv_encoding.h
> @@ -389,6 +389,9 @@
>  /* VS-Level Control transfer records CSRs */
>  #define CSR_VSCTRCTL                    0x24e
>
> +/* Supervisor Resource Management Configuration CSRs */
> +#define CSR_SRMCFG                     0x181
> +
>  /* ===== Hypervisor-level CSRs ===== */
>
>  /* Hypervisor Trap Setup (H-extension) */
> @@ -815,6 +818,8 @@
>  #define SMSTATEEN0_FCSR                        (_ULL(1) << SMSTATEEN0_FCSR_SHIFT)
>  #define SMSTATEEN0_CTR_SHIFT           54
>  #define SMSTATEEN0_CTR                 (_ULL(1) << SMSTATEEN0_CTR_SHIFT)
> +#define SMSTATEEN0_SRMCFG_SHIFT                55
> +#define SMSTATEEN0_SRMCFG              (_ULL(1) << SMSTATEEN0_SRMCFG_SHIFT)
>  #define SMSTATEEN0_CONTEXT_SHIFT       57
>  #define SMSTATEEN0_CONTEXT             (_ULL(1) << SMSTATEEN0_CONTEXT_SHIFT)
>  #define SMSTATEEN0_IMSIC_SHIFT         58
> diff --git a/include/sbi/sbi_hart.h b/include/sbi/sbi_hart.h
> index 82b19dc..ff501f5 100644
> --- a/include/sbi/sbi_hart.h
> +++ b/include/sbi/sbi_hart.h
> @@ -81,6 +81,8 @@ enum sbi_hart_extensions {
>         SBI_HART_EXT_SSCTR,
>         /** HART has Ssstateen extension **/
>         SBI_HART_EXT_SSSTATEEN,
> +       /** Hart has Ssqosid extension */
> +       SBI_HART_EXT_SSQOSID,
>
>         /** Maximum index of Hart extension */
>         SBI_HART_EXT_MAX,
> diff --git a/lib/sbi/sbi_hart.c b/lib/sbi/sbi_hart.c
> index c085804..aaf922b 100644
> --- a/lib/sbi/sbi_hart.c
> +++ b/lib/sbi/sbi_hart.c
> @@ -110,6 +110,11 @@ static void mstatus_init(struct sbi_scratch *scratch)
>                 else
>                         mstateen_val &= ~SMSTATEEN0_CTR;
>
> +               if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SSQOSID))
> +                       mstateen_val |= (SMSTATEEN0_SRMCFG);
> +               else
> +                       mstateen_val &= ~(SMSTATEEN0_SRMCFG);
> +

Since we are enabling Srmcfg CSR for S-mode, we should also context
switch it in the switch_to_next_domain_context() function.

>                 csr_write64(CSR_MSTATEEN0, mstateen_val);
>                 csr_write64(CSR_MSTATEEN1, SMSTATEEN_STATEN);
>                 csr_write64(CSR_MSTATEEN2, SMSTATEEN_STATEN);
> @@ -727,6 +732,7 @@ const struct sbi_hart_ext_data sbi_hart_ext[] = {
>         __SBI_HART_EXT_DATA(smctr, SBI_HART_EXT_SMCTR),
>         __SBI_HART_EXT_DATA(ssctr, SBI_HART_EXT_SSCTR),
>         __SBI_HART_EXT_DATA(ssstateen, SBI_HART_EXT_SSSTATEEN),
> +       __SBI_HART_EXT_DATA(ssqosid, SBI_HART_EXT_SSQOSID),
>  };
>
>  _Static_assert(SBI_HART_EXT_MAX == array_size(sbi_hart_ext),
> @@ -989,6 +995,9 @@ __pmp_skip:
>         /* Detect if hart supports smcntrpmf */
>         __check_ext_csr(SBI_HART_PRIV_VER_1_12,
>                         CSR_MCYCLECFG, SBI_HART_EXT_SMCNTRPMF);
> +       /* Detect if hart supports ssqosid */
> +       __check_ext_csr(SBI_HART_PRIV_VER_1_12,
> +                       CSR_SRMCFG, SBI_HART_EXT_SSQOSID);

For newer extensions, detecting from ISA string is sufficient so no need
to trap-n-detect here.

>         /* Detect if hart support sdtrig (debug triggers) */
>         __check_ext_csr(SBI_HART_PRIV_VER_UNKNOWN,
>                         CSR_TSELECT, SBI_HART_EXT_SDTRIG);
> --
> 2.49.0
>

Regards,
Anup