[PATCH v4 3/3] lib: sbi: domain FP/Vector context support for context switch

[Anup Patel]

On Wed, May 13, 2026 at 12:44 PM <dave.patel at riscstar.com> wrote:
>
> From: Dave Patel <dave.patel at riscstar.com>
>
> This patch adds proper support for per-domain floating-point (FP) and
> vector (V) contexts in the domain context switch logic. Each domain
> now maintains its own FP and vector state, which is saved and restored
> during domain switches.
>
> Changes include:
>
> - Added `fp_ctx` and `vec_ctx` members to `struct hart_context`.
> - Introduced dynamic vector struct allocation for vlenb in 'struct hart_context'
>   to allocate and free per-domain FP and vector context.
> - Modified `sbi_domain_register()` to initialize FP/Vector context per domain.
> - Updated `switch_to_next_domain_context()` to save/restore FP and vector
>   contexts safely:
>     - Ensures FS/VS fields in `mstatus` are enabled (set to Initial) only if Off.
> - Added runtime checks for FP and vector extensions where needed.
>
> This improves support for multi-domain systems with FP and Vector
> extensions, and prevents corruption of FP/Vector state during domain
> switches.
>
> Signed-off-by: Dave Patel <dave.patel at riscstar.com>
> ---
>  include/sbi/sbi_domain.h     |  2 ++
>  lib/sbi/sbi_domain_context.c | 28 ++++++++++++++++++++++++++++
>  2 files changed, 30 insertions(+)
>
> diff --git a/include/sbi/sbi_domain.h b/include/sbi/sbi_domain.h
> index 882b62c2..05a5d86c 100644
> --- a/include/sbi/sbi_domain.h
> +++ b/include/sbi/sbi_domain.h
> @@ -16,6 +16,8 @@
>  #include <sbi/sbi_hartmask.h>
>  #include <sbi/sbi_domain_context.h>
>  #include <sbi/sbi_domain_data.h>
> +#include <sbi/sbi_vector.h>
> +#include <sbi/sbi_fp.h>
>
>  struct sbi_scratch;
>
> diff --git a/lib/sbi/sbi_domain_context.c b/lib/sbi/sbi_domain_context.c
> index 158f4990..5e180698 100644
> --- a/lib/sbi/sbi_domain_context.c
> +++ b/lib/sbi/sbi_domain_context.c
> @@ -18,6 +18,9 @@
>  #include <sbi/sbi_domain_context.h>
>  #include <sbi/sbi_platform.h>
>  #include <sbi/sbi_trap.h>
> +#include <sbi/sbi_vector.h>
> +#include <sbi/sbi_fp.h>
> +
>
>  /** Context representation for a hart within a domain */
>  struct hart_context {
> @@ -55,6 +58,11 @@ struct hart_context {
>         struct hart_context *prev_ctx;
>         /** Is context initialized and runnable */
>         bool initialized;
> +
> +       /** float context state */
> +       struct sbi_fp_context fp_ctx;
> +       /** vector context state */
> +       struct sbi_vector_context *vec_ctx;
>  };
>
>  static struct sbi_domain_data dcpriv;
> @@ -143,6 +151,15 @@ static int switch_to_next_domain_context(struct hart_context *ctx,
>         if (sbi_hart_has_extension(scratch, SBI_HART_EXT_SSQOSID))
>                 ctx->srmcfg     = csr_swap(CSR_SRMCFG, dom_ctx->srmcfg);
>
> +       /* Make sure FS and VS is on before context switch */
> +       csr_set(CSR_MSTATUS, MSTATUS_FS | MSTATUS_VS);
> +
> +       /* Eager context switch F and V */
> +       sbi_fp_save(&ctx->fp_ctx);
> +       sbi_fp_restore(&dom_ctx->fp_ctx);
> +       sbi_vector_save(ctx->vec_ctx);
> +       sbi_vector_restore(dom_ctx->vec_ctx);
> +
>         /* Save current trap state and restore target domain's trap state */
>         trap_ctx = sbi_trap_get_context(scratch);
>         sbi_memcpy(&ctx->trap_ctx, trap_ctx, sizeof(*trap_ctx));
> @@ -170,6 +187,10 @@ static int hart_context_init(u32 hartindex)
>  {
>         struct hart_context *ctx;
>         struct sbi_domain *dom;
> +       unsigned long vlenb = vector_vlenb();
> +
> +       /* Calculate size: base struct + 32 registers of vlenb size */
> +       size_t vec_size = sizeof(struct sbi_vector_context) + (32 * vlenb);

Call vector_vlenb() and allocate vec_ctx only when
underlying HART has SBI_HART_EXT_V.

>
>         sbi_domain_for_each(dom) {
>                 if (!sbi_hartmask_test_hartindex(hartindex,
> @@ -180,6 +201,13 @@ static int hart_context_init(u32 hartindex)
>                 if (!ctx)
>                         return SBI_ENOMEM;
>
> +               /* Allocate the vector context pointer */
> +               ctx->vec_ctx = sbi_zalloc(vec_size);
> +               if (!ctx->vec_ctx) {
> +                       sbi_free(ctx);
> +                       return SBI_ENOMEM;
> +               }
> +
>                 /* Bind context and domain */
>                 ctx->dom = dom;
>                 hart_context_set(dom, hartindex, ctx);
> --
> 2.43.0
>
>
> --
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Regards,
Anup