Re: [Xen-devel] Bringing up sequence for non-boot CPU fails

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-02-18 at 13:44 +0200, Oleksandr Tyshchenko wrote:

> +GLOBAL(enter_hyp_mode)
> +enter_hyp_mode:
> +        adr   r0, save
> +        stmea r0, {r4-r13,lr}
> +        ldr   r12, =0x102
> +        adr   r0, hyp_return
> +        dsb
> +        isb
> +        dmb
> +        smc   #0

Who/what implements this handler?

> +hyp_return:
> +        adr   r0, save
> +        ldmfd r0, {r4-r13,pc}
> +save:
> +        .rept 11
> +        .word 0
> +        .endr
> +
>  /*
>   * Local variables:
>   * mode: ASM
> 
> 
> Please, could anyone give me advice about this issue?

Do you have any hardware debugging tools which could give some insight?

Usually these things are down to either missing cache flushes or
barriers, but tracking them down has historically been a total pain.

>  And what do you
> think about solution to exit from busy loop by timeout and restart
> CPU1 bringing up sequence in this case?

A timeout isn't a bad idea, although I would not be inclined to try
again with the CPU in an indeterminate state.

Either we should carry on without it or we should panic (which is more
obvious than a hang). I think carrying on would be surprising (you'd
only get half the processing power you expected).

Ian.


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