Re: [XEN PATCH v4 3/4] xen/x86: address violations of MISRA C:2012 Rule 13.1

[Jan Beulich <jbeulich@xxxxxxxx>]

On 02.02.2024 16:16, Simone Ballarin wrote:
> Rule 13.1: Initializer lists shall not contain persistent side effects
> 
> This patch moves expressions with side-effects into new variables before
> the initializer lists.
> 
> No functional changes.
> 
> Signed-off-by: Simone Ballarin <simone.ballarin@xxxxxxxxxxx>

To be honest, I don't like this. It's more code for no gain. Really its
hampering clarity imo. I'm willing to be convinced otherwise, but for
now this gets a nack from me.

As an aside, ...

> --- a/xen/arch/x86/io_apic.c
> +++ b/xen/arch/x86/io_apic.c
> @@ -2559,9 +2559,12 @@ integer_param("max_gsi_irqs", max_gsi_irqs);
>  
>  static __init bool bad_ioapic_register(unsigned int idx)
>  {
> -    union IO_APIC_reg_00 reg_00 = { .raw = io_apic_read(idx, 0) };
> -    union IO_APIC_reg_01 reg_01 = { .raw = io_apic_read(idx, 1) };
> -    union IO_APIC_reg_02 reg_02 = { .raw = io_apic_read(idx, 2) };
> +    uint32_t reg_00_raw = io_apic_read(idx, 0);
> +    uint32_t reg_01_raw = io_apic_read(idx, 1);
> +    uint32_t reg_02_raw = io_apic_read(idx, 2);

... while you properly use uint32_t here, ...

> +    union IO_APIC_reg_00 reg_00 = { .raw = reg_00_raw };
> +    union IO_APIC_reg_01 reg_01 = { .raw = reg_01_raw };
> +    union IO_APIC_reg_02 reg_02 = { .raw = reg_02_raw };
>  
>      if ( reg_00.raw == -1 && reg_01.raw == -1 && reg_02.raw == -1 )
>      {
> --- a/xen/arch/x86/mpparse.c
> +++ b/xen/arch/x86/mpparse.c
> @@ -798,11 +798,12 @@ void __init mp_register_lapic_address (
>  
>  int mp_register_lapic(u32 id, bool enabled, bool hotplug)
>  {
> +     u32 apic = apic_read(APIC_LVR);

... why the being-phased-out u32 here?

Jan

>       struct mpc_config_processor processor = {
>               .mpc_type = MP_PROCESSOR,
>               /* Note: We don't fill in fields not consumed anywhere. */
>               .mpc_apicid = id,
> -             .mpc_apicver = GET_APIC_VERSION(apic_read(APIC_LVR)),
> +             .mpc_apicver = GET_APIC_VERSION(apic),
>               .mpc_cpuflag = (enabled ? CPU_ENABLED : 0) |
>                              (id == boot_cpu_physical_apicid ?
>                               CPU_BOOTPROCESSOR : 0),
> --- a/xen/arch/x86/setup.c
> +++ b/xen/arch/x86/setup.c
> @@ -885,13 +885,14 @@ static struct domain *__init create_dom0(const module_t 
> *image,
>  {
>      static char __initdata cmdline[MAX_GUEST_CMDLINE];
>  
> +    unsigned int max_vcpus = dom0_max_vcpus();
>      struct xen_domctl_createdomain dom0_cfg = {
>          .flags = IS_ENABLED(CONFIG_TBOOT) ? XEN_DOMCTL_CDF_s3_integrity : 0,
>          .max_evtchn_port = -1,
>          .max_grant_frames = -1,
>          .max_maptrack_frames = -1,
>          .grant_opts = XEN_DOMCTL_GRANT_version(opt_gnttab_max_version),
> -        .max_vcpus = dom0_max_vcpus(),
> +        .max_vcpus = max_vcpus,
>          .arch = {
>              .misc_flags = opt_dom0_msr_relaxed ? XEN_X86_MSR_RELAXED : 0,
>          },