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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Tue, 6 Feb 2024, Jan Beulich wrote:
> 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.

Which part of the patch you don't like? The changes to
bad_ioapic_register?



> 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,
> >          },
>