Re: [PATCH for-next 3/6] xen/sched: Fix build when NR_CPUS == 1

[Connor Davis <connojdavis@gmail.com>]

On Thu, Feb 25, 2021 at 02:55:45PM -0800, Bob Eshleman wrote:
> On 2/25/21 7:24 AM, Connor Davis wrote:
> > Return from cpu_schedule_up when either cpu is 0 or
> > NR_CPUS == 1. This fixes the following:
> > 
> > core.c: In function 'cpu_schedule_up':
> > core.c:2769:19: error: array subscript 1 is above array bounds
> > of 'struct vcpu *[1]' [-Werror=array-bounds]
> >  2769 |     if ( idle_vcpu[cpu] == NULL )
> >       |
> > 
> > Signed-off-by: Connor Davis <connojdavis@gmail.com>
> > ---
> >  xen/common/sched/core.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/xen/common/sched/core.c b/xen/common/sched/core.c
> > index 9745a77eee..f5ec65bf9b 100644
> > --- a/xen/common/sched/core.c
> > +++ b/xen/common/sched/core.c
> > @@ -2763,7 +2763,7 @@ static int cpu_schedule_up(unsigned int cpu)
> >      cpumask_set_cpu(cpu, &sched_res_mask);
> >  
> >      /* Boot CPU is dealt with later in scheduler_init(). */
> > -    if ( cpu == 0 )
> > +    if ( cpu == 0 || NR_CPUS == 1 )
> >          return 0;
> >  
> >      if ( idle_vcpu[cpu] == NULL )
> > 
> 
> Interesting.  I wonder when this changed in GCC.
> 
> I haven't yet seen this issue compiling with:
>   NR_CPUS=1
>   ARCH=riscv64
>   riscv64-unknown-linux-gnu-gcc (GCC) 10.1.0
> 
> Which version of GCC are you seeing emit this?

The one from cloned from github.com/riscv/riscv-gnu-toolchain
in the docker container uses 10.2.0

    Connor