Re: [Xen-devel] [PATCH] x86/xen: Improve failed hypercall debugging

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 05/02/2017 01:59 PM, Andy Lutomirski wrote:
> When fiddling with xen_exit_mmap(), I noticed that failed multicall
> debugging doesn't work if the multicall is just one call.  Fix it.

That wouldn't be a multicall though, we'll end up making the desired
hypercall directly.

Besides,  b->debug[] is not initialized in this case.

-boris

>
> Cc: Juergen Gross <jgross@xxxxxxxx>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
> Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxx>
> ---
>  arch/x86/xen/multicalls.c | 26 +++++++++++++-------------
>  1 file changed, 13 insertions(+), 13 deletions(-)
>
> diff --git a/arch/x86/xen/multicalls.c b/arch/x86/xen/multicalls.c
> index ea54a08d8301..b6b3f024d342 100644
> --- a/arch/x86/xen/multicalls.c
> +++ b/arch/x86/xen/multicalls.c
> @@ -96,23 +96,23 @@ void xen_mc_flush(void)
>               for (i = 0; i < b->mcidx; i++)
>                       if (b->entries[i].result < 0)
>                               ret++;
> +     }
>  
>  #if MC_DEBUG
> -             if (ret) {
> -                     printk(KERN_ERR "%d multicall(s) failed: cpu %d\n",
> -                            ret, smp_processor_id());
> -                     dump_stack();
> -                     for (i = 0; i < b->mcidx; i++) {
> -                             printk(KERN_DEBUG "  call %2d/%d: op=%lu 
> arg=[%lx] result=%ld\t%pF\n",
> -                                    i+1, b->mcidx,
> -                                    b->debug[i].op,
> -                                    b->debug[i].args[0],
> -                                    b->entries[i].result,
> -                                    b->caller[i]);
> -                     }
> +     if (ret) {
> +             printk(KERN_ERR "%d multicall(s) failed: cpu %d\n",
> +                    ret, smp_processor_id());
> +             dump_stack();
> +             for (i = 0; i < b->mcidx; i++) {
> +                     printk(KERN_DEBUG "  call %2d/%d: op=%lu arg=[%lx] 
> result=%ld\t%pF\n",
> +                            i+1, b->mcidx,
> +                            b->debug[i].op,
> +                            b->debug[i].args[0],
> +                            b->entries[i].result,
> +                            b->caller[i]);
>               }
> -#endif
>       }
> +#endif
>  
>       b->mcidx = 0;
>       b->argidx = 0;


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