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

[Wei Chen <Wei.Chen@xxxxxxx>]

Hi Stefano,

On 2017/3/21 5:44, Stefano Stabellini wrote:
> On Mon, 20 Mar 2017, Stefano Stabellini wrote:
>> 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?
>
> I can see from the following patches that both situations are a risk.
> Although the patch could benefit from a better commit description:
>
> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>
>

Thanks, I will update the commit message in next version.

>
>>> 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
>>>
>>>
>>> _______________________________________________
>>> Xen-devel mailing list
>>> Xen-devel@xxxxxxxxxxxxx
>>> https://lists.xen.org/xen-devel
>>>
>>
>


-- 
Regards,
Wei Chen

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