Re: [Xen-devel] [PATCH 15/18] xen/arm: Introduce a helper to synchronize SError

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 13 Mar 2017, Wei Chen wrote:
> We may have to isolate the SError between the context switch of
> 2 vCPUs or may have to prevent slipping hypervisor SError to guest.

I thought the problem is not the risk of slipping hypervisor SErrors to
guest, but the risk of slipping previous guest SErrors to the next
guest. Is that right?


> So we need a helper to synchronize SError before context switching
> or returning to guest.
> 
> This function will be used by the later patches in this series, we
> use "#if 0" to disable it temporarily to remove compiler warnning.
> 
> Signed-off-by: Wei Chen <Wei.Chen@xxxxxxx>
> ---
>  xen/arch/arm/traps.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
> index 44a0281..ee7865b 100644
> --- a/xen/arch/arm/traps.c
> +++ b/xen/arch/arm/traps.c
> @@ -2899,6 +2899,17 @@ asmlinkage void do_trap_hypervisor(struct 
> cpu_user_regs *regs)
>      }
>  }
>  
> +#if 0
> +static void synchronize_serror(void)
> +{
> +    /* Synchronize against in-flight ld/st. */
> +    dsb(sy);
> +
> +    /* A single instruction exception window */
> +    isb();
> +}
> +#endif
> +
>  asmlinkage void do_trap_hyp_serror(struct cpu_user_regs *regs)
>  {
>      enter_hypervisor_head(regs);
> -- 
> 2.7.4
> 
> 
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