[kvm-unit-tests PATCH 4/7] riscv: Add ACPI support for ISA string discovery

[Andrew Jones]

On Thu, Sep 24, 2026 at 11:39:42AM +0800, Xiang W wrote:
> When a DT is not provided, walk the RHCT Hart Info nodes and parse
> the referenced ISA String node instead of aborting in isa_init()
> and cpu_has_extension_name().
> 
> Match the current hart by ACPI UID (DT still matches by hartid)
> and feed the ISA string into the existing isa_parse() helper so
> extension detection is shared by both firmware descriptions.
> 
> Rename isa_info.hartid to isa_info.id so the same iterator state
> can hold either identifier.
> 
> Signed-off-by: Xiang W <wangxiang at iscas.ac.cn>
> ---
>  lib/acpi.h      | 28 ++++++++++++++++++++
>  lib/riscv/isa.c | 68 ++++++++++++++++++++++++++++++++++++++++++++-----
>  2 files changed, 89 insertions(+), 7 deletions(-)
> 
> diff --git a/lib/acpi.h b/lib/acpi.h
> index 2597e8ce..3db382b7 100644
> --- a/lib/acpi.h
> +++ b/lib/acpi.h
> @@ -337,6 +337,34 @@ struct acpi_table_rhct {
>  	u32 node_offset;
>  };
>  
> +#define ACPI_RHCT_NODE_HEADER_DEF \
> +	u16 type;	\
> +	u16 length;	\
> +	u16 revision;	\
> +
> +struct acpi_rhct_node {
> +	ACPI_RHCT_NODE_HEADER_DEF
> +	char data[];
> +};
> +
> +enum acpi_rhct_node_type {
> +	RHCT_NODE_ISA_STRING = 0x0,
> +	RHCT_NODE_HART_INFO = 0xFFFF

ACPI_RHCT_NODE_TYPE_ISA_STRING
ACPI_RHCT_NODE_TYPE_HART_INFO

> +};
> +
> +struct acpi_rhct_node_isa_string {
> +	ACPI_RHCT_NODE_HEADER_DEF
> +	u16 isa_length;
> +	char isa[];
> +};
> +
> +struct acpi_rhct_node_hart_info {
> +	ACPI_RHCT_NODE_HEADER_DEF
> +	u16 num_offsets;
> +	u32 uid;
> +	u32 nodes[];
> +};
> +
>  /* Reset to default packing */
>  #pragma pack()
>  
> diff --git a/lib/riscv/isa.c b/lib/riscv/isa.c
> index bc1c9c72..b0257979 100644
> --- a/lib/riscv/isa.c
> +++ b/lib/riscv/isa.c
> @@ -12,7 +12,7 @@
>  typedef void (*isa_func_t)(const char *, int, void *);
>  
>  struct isa_info {
> -	unsigned long hartid;
> +	unsigned long id;
>  	isa_func_t func;
>  	void *data;
>  };
> @@ -74,7 +74,7 @@ static void isa_parse_fdt(int cpu_node, u64 hartid, void *data)
>  	const struct fdt_property *prop;
>  	int len;
>  
> -	if (hartid != info->hartid)
> +	if (hartid != info->id)
>  		return;
>  
>  	prop = fdt_get_property(dt_fdt(), cpu_node, "riscv,isa", &len);
> @@ -83,32 +83,80 @@ static void isa_parse_fdt(int cpu_node, u64 hartid, void *data)
>  	isa_parse(prop->data, len, info);
>  }
>  
> -static void isa_init_acpi(void)
> +#ifdef CONFIG_EFI
> +#include <acpi.h>
> +
> +static void isa_parse_acpi(struct acpi_table_rhct *rhct, struct acpi_rhct_node_hart_info *hart_info, void *data)

Let's keep it under 100

static void isa_parse_acpi(struct acpi_table_rhct *rhct,
			   struct acpi_rhct_node_hart_info *hart_info, void *data)

> +{
> +	u32 offset;
> +	struct acpi_rhct_node *node;
> +	struct acpi_rhct_node_isa_string *isa_string;
> +	struct isa_info *info = (struct isa_info *)data;
> +
> +	if (hart_info->uid != info->id)
> +		return;
> +
> +	for (int i = 0; i < hart_info->num_offsets; i++) {
> +		offset = hart_info->nodes[i];
> +		if (offset >= rhct->length)
> +			break;
> +		node = (void *)rhct + offset;
> +		if (node->type == RHCT_NODE_ISA_STRING) {
> +			isa_string = (void *) node;

 isa_string = (void *)node

I thought checkpatch would catch something like that. Did you run it?

> +			isa_parse(isa_string->isa, isa_string->isa_length, info);
> +		}
> +	}
> +}
> +
> +static void acpi_rhct_for_each_hart(
> +	void (*func)(struct acpi_table_rhct *, struct acpi_rhct_node_hart_info *, void *), void *data)

static void acpi_rhct_for_each_hart(void (*func)(struct acpi_table_rhct *,
						 struct acpi_rhct_node_hart_info *,
						 void *), void *data)

>  {
> -	assert_msg(false, "ACPI not available");
> +	u32 offset;
> +	struct acpi_table_rhct *rhct;
> +	struct acpi_rhct_node *node;
> +	struct acpi_rhct_node_hart_info *hart_info;

Need a blank line here. I'm thinking checkpatch wasn't run, since I'm sure
that would have been caught.

Thanks,
drew