Re: [PATCH v6 1/7] arm64: cpufeature: Detect CPU RAS Extentions

gengdongjiu
2017-09-04T11:20:26Z

James,

On 2017/9/1 1:44, James Morse wrote:
> Hi Dongjiu Geng,
>
> On 28/08/17 11:38, Dongjiu Geng wrote:
>> From: Xie XiuQi <xiexiuqi@huawei.com>
>>
>> ARM's v8.2 Extentions add support for Reliability, Availability and
>> Serviceability (RAS). On CPUs with these extensions system software
>> can use additional barriers to isolate errors and determine if faults
>> are pending.
>>
>> Add cpufeature detection and a barrier in the context-switch code.
>> There is no need to use alternatives for this as CPUs that don't
>> support this feature will treat the instruction as a nop.
>>
>> Platform level RAS support may require additional firmware support.
>>
>> Signed-off-by: Xie XiuQi <xiexiuqi@huawei.com>
>> [Rebased, added esb and config option, reworded commit message]
>> Signed-off-by: James Morse <james.morse@arm.com>
>
> Nit: when re-posting patches from the list you need to add your signed-off-by.
> See Documentation/process/submitting-patches.rst 'Developer's Certificate of
> Origin 1.1'
Ok, thanks for the your pointing out.

>
> This goes for your patch 2 as well.
>
>
>> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
>> index c845c8c04d95..7a17b4a1bd9e 100644
>> --- a/arch/arm64/kernel/process.c
>> +++ b/arch/arm64/kernel/process.c
>> @@ -370,6 +370,9 @@ __notrace_funcgraph struct task_struct *__switch_to(struct task_struct *prev,
>> */
>> dsb(ish);
>>
>> + /* Deliver any pending SError from prev */
>> + esb();
>> +
>
> This patch was sitting on top of the SError rework. As the cover-letter
> describes that was all there to make sure SError is unmasked when we execute
> this esb(). Without it any pending SError will be deferred, its ESR is written
> to DISR_EL1, which this patch doesn't check.
>
> On its own, this patch is actively harmful to systems that don't have
> firmware-first handling.
>
> We probably need to produce a combined series...
OK, thanks for your reminder and detailed explanation.

>
>
> Thanks,
>
> James
>
>
> .
>