Re: [PATCH v2 01/17] riscv: cpufeature: Fix thead vector hwcap removal

[Conor Dooley]

On Mon, Apr 15, 2024 at 09:11:58PM -0700, Charlie Jenkins wrote:
> The riscv_cpuinfo struct that contains mvendorid and marchid is not
> populated until all harts are booted which happens after the DT parsing.
> Use the vendorid/archid values from the DT if available or assume all
> harts have the same values as the boot hart as a fallback.
> 
> Fixes: d82f32202e0d ("RISC-V: Ignore V from the riscv,isa DT property on older T-Head CPUs")
> Signed-off-by: Charlie Jenkins <charlie@xxxxxxxxxxxx>
> ---
>  arch/riscv/include/asm/sbi.h   |  2 ++
>  arch/riscv/kernel/cpu.c        | 36 ++++++++++++++++++++++++++++++++----
>  arch/riscv/kernel/cpufeature.c | 12 ++++++++++--
>  3 files changed, 44 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/riscv/include/asm/sbi.h b/arch/riscv/include/asm/sbi.h
> index 6e68f8dff76b..0fab508a65b3 100644
> --- a/arch/riscv/include/asm/sbi.h
> +++ b/arch/riscv/include/asm/sbi.h
> @@ -370,6 +370,8 @@ static inline int sbi_remote_fence_i(const struct cpumask *cpu_mask) { return -1
>  static inline void sbi_init(void) {}
>  #endif /* CONFIG_RISCV_SBI */
>  
> +unsigned long riscv_get_mvendorid(void);
> +unsigned long riscv_get_marchid(void);
>  unsigned long riscv_cached_mvendorid(unsigned int cpu_id);
>  unsigned long riscv_cached_marchid(unsigned int cpu_id);
>  unsigned long riscv_cached_mimpid(unsigned int cpu_id);
> diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
> index d11d6320fb0d..8c8250b98752 100644
> --- a/arch/riscv/kernel/cpu.c
> +++ b/arch/riscv/kernel/cpu.c
> @@ -139,6 +139,34 @@ int riscv_of_parent_hartid(struct device_node *node, unsigned long *hartid)
>  	return -1;
>  }
>  
> +unsigned long __init riscv_get_marchid(void)
> +{
> +	struct riscv_cpuinfo *ci = this_cpu_ptr(&riscv_cpuinfo);
> +
> +#if IS_ENABLED(CONFIG_RISCV_SBI)
> +	ci->marchid = sbi_spec_is_0_1() ? 0 : sbi_get_marchid();
> +#elif IS_ENABLED(CONFIG_RISCV_M_MODE)
> +	ci->marchid = csr_read(CSR_MARCHID);
> +#else
> +	ci->marchid = 0;
> +#endif
> +	return ci->marchid;
> +}
> +
> +unsigned long __init riscv_get_mvendorid(void)
> +{
> +	struct riscv_cpuinfo *ci = this_cpu_ptr(&riscv_cpuinfo);
> +
> +#if IS_ENABLED(CONFIG_RISCV_SBI)
> +	ci->mvendorid = sbi_spec_is_0_1() ? 0 : sbi_get_mvendorid();
> +#elif IS_ENABLED(CONFIG_RISCV_M_MODE)
> +	ci->mvendorid = csr_read(CSR_MVENDORID);
> +#else
> +	ci->mvendorid = 0;
> +#endif
> +	return ci->mvendorid;
> +}
> +
>  DEFINE_PER_CPU(struct riscv_cpuinfo, riscv_cpuinfo);
>  
>  unsigned long riscv_cached_mvendorid(unsigned int cpu_id)
> @@ -170,12 +198,12 @@ static int riscv_cpuinfo_starting(unsigned int cpu)
>  	struct riscv_cpuinfo *ci = this_cpu_ptr(&riscv_cpuinfo);
>  
>  #if IS_ENABLED(CONFIG_RISCV_SBI)
> -	ci->mvendorid = sbi_spec_is_0_1() ? 0 : sbi_get_mvendorid();
> -	ci->marchid = sbi_spec_is_0_1() ? 0 : sbi_get_marchid();
> +	ci->mvendorid = ci->mvendorid ? ci->mvendorid : sbi_spec_is_0_1() ? 0 : sbi_get_mvendorid();
> +	ci->marchid = ci->marchid ? ci->marchid : sbi_spec_is_0_1() ? 0 : sbi_get_marchid();

Can we please not have double ternary stuff? This is awful to grok :(
Can you do
if (!ci->m*id)
	sbi_spec_is_0_1() ? 0 : sbi_get_m*id();
instead? I think that is much easier to understand.
Otherwise,
Reviewed-by: Conor Dooley <conor.dooley@xxxxxxxxxxxxx>

Cheers,
Conor.

>  	ci->mimpid = sbi_spec_is_0_1() ? 0 : sbi_get_mimpid();
>  #elif IS_ENABLED(CONFIG_RISCV_M_MODE)
> -	ci->mvendorid = csr_read(CSR_MVENDORID);
> -	ci->marchid = csr_read(CSR_MARCHID);
> +	ci->mvendorid = ci->mvendorid ? ci->mvendorid : csr_read(CSR_MVENDORID);
> +	ci->marchid = ci->marchid ? ci->marchid : csr_read(CSR_MARCHID);
>  	ci->mimpid = csr_read(CSR_MIMPID);
>  #else
>  	ci->mvendorid = 0;
> diff --git a/arch/riscv/kernel/cpufeature.c b/arch/riscv/kernel/cpufeature.c
> index 3ed2359eae35..c6e27b45e192 100644
> --- a/arch/riscv/kernel/cpufeature.c
> +++ b/arch/riscv/kernel/cpufeature.c
> @@ -490,6 +490,8 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
>  	struct acpi_table_header *rhct;
>  	acpi_status status;
>  	unsigned int cpu;
> +	u64 boot_vendorid;
> +	u64 boot_archid;
>  
>  	if (!acpi_disabled) {
>  		status = acpi_get_table(ACPI_SIG_RHCT, 0, &rhct);
> @@ -497,6 +499,13 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
>  			return;
>  	}
>  
> +	/*
> +	 * Naively assume that all harts have the same mvendorid/marchid as the
> +	 * boot hart.
> +	 */
> +	boot_vendorid = riscv_get_mvendorid();
> +	boot_archid = riscv_get_marchid();
> +
>  	for_each_possible_cpu(cpu) {
>  		struct riscv_isainfo *isainfo = &hart_isa[cpu];
>  		unsigned long this_hwcap = 0;
> @@ -544,8 +553,7 @@ static void __init riscv_fill_hwcap_from_isa_string(unsigned long *isa2hwcap)
>  		 * CPU cores with the ratified spec will contain non-zero
>  		 * marchid.
>  		 */
> -		if (acpi_disabled && riscv_cached_mvendorid(cpu) == THEAD_VENDOR_ID &&
> -		    riscv_cached_marchid(cpu) == 0x0) {
> +		if (acpi_disabled && boot_vendorid == THEAD_VENDOR_ID && boot_archid == 0x0) {
>  			this_hwcap &= ~isa2hwcap[RISCV_ISA_EXT_v];
>  			clear_bit(RISCV_ISA_EXT_v, isainfo->isa);
>  		}
> 
> -- 
> 2.44.0
>

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