Re: [kvm-unit-tests PATCH v1 2/5] lib: s390x: smp: guarantee that boot CPU has index 0

[David Hildenbrand <david@redhat.com>]

On 28.01.22 19:54, Claudio Imbrenda wrote:
> Guarantee that the boot CPU has index 0. This simplifies the
> implementation of tests that require multiple CPUs.
> 
> Also fix a small bug in the allocation of the cpus array.
> 
> Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
> Fixes: f77c0515 ("s390x: Add initial smp code")
> Fixes: 52076a63 ("s390x: Consolidate sclp read info")
> ---
>  lib/s390x/smp.c | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
> 
> diff --git a/lib/s390x/smp.c b/lib/s390x/smp.c
> index 64c647ec..01f513f0 100644
> --- a/lib/s390x/smp.c
> +++ b/lib/s390x/smp.c
> @@ -25,7 +25,6 @@
>  #include "sclp.h"
>  
>  static struct cpu *cpus;
> -static struct cpu *cpu0;
>  static struct spinlock lock;
>  
>  extern void smp_cpu_setup_state(void);
> @@ -81,7 +80,7 @@ static int smp_cpu_stop_nolock(uint16_t addr, bool store)
>  	uint8_t order = store ? SIGP_STOP_AND_STORE_STATUS : SIGP_STOP;
>  
>  	cpu = smp_cpu_from_addr(addr);
> -	if (!cpu || cpu == cpu0)
> +	if (!cpu || addr == cpus[0].addr)
>  		return -1;
>  
>  	if (sigp_retry(addr, order, 0, NULL))
> @@ -205,7 +204,7 @@ int smp_cpu_setup(uint16_t addr, struct psw psw)
>  	sigp_retry(cpu->addr, SIGP_SET_PREFIX, (unsigned long )lc, NULL);
>  
>  	/* Copy all exception psws. */
> -	memcpy(lc, cpu0->lowcore, 512);
> +	memcpy(lc, cpus[0].lowcore, 512);
>  
>  	/* Setup stack */
>  	cpu->stack = (uint64_t *)alloc_pages(2);
> @@ -263,15 +262,16 @@ void smp_setup(void)
>  	if (num > 1)
>  		printf("SMP: Initializing, found %d cpus\n", num);
>  
> -	cpus = calloc(num, sizeof(cpus));
> +	cpus = calloc(num, sizeof(*cpus));
>  	for (i = 0; i < num; i++) {
>  		cpus[i].addr = entry[i].address;
>  		cpus[i].active = false;
>  		if (entry[i].address == cpu0_addr) {
> -			cpu0 = &cpus[i];
> -			cpu0->stack = stackptr;
> -			cpu0->lowcore = (void *)0;
> -			cpu0->active = true;
> +			cpus[i].addr = cpus[0].addr;

Might deserve a comment that we'll move the the boot CPU to index 0.

What's the expected behavior if i == 0?

-- 
Thanks,

David / dhildenb