Re: [PATCH 02/15] arm/kvm: add accessors for storing host features into idregs

[Richard Henderson]

On 2/7/25 03:02, Cornelia Huck wrote:
> +/* read a 32b sysreg value and store it in the idregs */
> +static int get_host_cpu_reg32(int fd, ARMHostCPUFeatures *ahcf, ARMSysRegs 
> sysreg)
> +{
> +    int index = get_sysreg_idx(sysreg);
> +    uint64_t *reg;
> +    int ret;
> +
> +    if (index < 0) {
> +        return -ERANGE;
> +    }
> +    reg = &ahcf->isar.idregs[index];
> +    ret = read_sys_reg32(fd, (uint32_t *)reg, 
> idregs_sysreg_to_kvm_reg(sysreg));
> +    return ret;
> +}
> +
> +/* read a 64b sysreg value and store it in the idregs */
> +static int get_host_cpu_reg64(int fd, ARMHostCPUFeatures *ahcf, ARMSysRegs 
> sysreg)
> +{
> +    int index = get_sysreg_idx(sysreg);

Why pass the ARMSysRegs value instead of the ARMIDRegisterIdx value?

You save yourself a linear search over the id_register_sysreg array, and you can't use 
this interface with a sysreg that doesn't have an index anyway -- ERANGE is a new failure 
mode.


r~