Re: [Xen-devel] [PATCH v3 18/19] xen/arm: Prevent slipping hypervisor SError to guest

[Julien Grall <julien.grall@xxxxxxx>]

Hi Wei,

On 31/03/17 14:07, Wei Chen wrote:
> If there is a pending SError while we're returning from trap. If the
> SError handle option is "DIVERSE", we have to prevent slipping this
> hypervisor SError to guest. So we have to use the dsb/isb to guarantee
> that the pending hypervisor SError would be caught in hypervisor before
> return to guest.
>
> In previous patch, we will set SKIP_CHECK_PENDING_VSERROR to cpu_hwcaps
> when option is NOT "DIVERSE". This means we can use the alternative to
> skip synchronizing SErrors for other SErrors handle options.
>
> Because we have umasked the Abort/SError bit in previous patch. We have
> to disable the Abort/SError before returning to guest as we have done
> for IRQ.
>
> Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
>
> ---
> v2->v3:
> 1. Use alternative instead of check serror_op to skip sychronizing SErrors
>    while option is NOT "DIVERSE".
> 2. Disable Abort/SError before returning to guest.
> ---
>  xen/arch/arm/traps.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
>
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 2c610c4..8f1a0cd 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -2936,6 +2936,19 @@ asmlinkage void leave_hypervisor_tail(void)
>          local_irq_disable();
>          if (!softirq_pending(smp_processor_id())) {
>              gic_inject();
> +
> +            /*
> +             * If the SErrors handle option is "DIVERSE", we have to prevent
> +             * slipping the hypervisor SError to guest. In this option, before
> +             * returning from trap, we have to synchronize SErrors to guarantee
> +             * that the pending SError would be caught in hypervisor.
> +             *
> +             * If option is NOT "DIVERSE", SKIP_CHECK_PENDING_VSERROR will be
> +             * set to cpu_hwcaps. This means we can use the alternative to skip
> +             * synchronizing SErrors for other SErrors handle options.
> +             */
> +            SYNCHRONIZE_SERROR(SKIP_CHECK_PENDING_VSERROR);
The feature name SKIP_CHECK_PENDING_VSERROR does not make sense here 
because we are not synchronizing guest SError.
I am happy to re-use the same feature, but this would need to rename. 
Maybe SKIP_SYNCHRONIZE_SERROR_ENTRY_EXIT?
> +
>              return;
>          }
>          local_irq_enable();
Cheers,

--
Julien Grall

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