From mboxrd@z Thu Jan  1 00:00:00 1970
From: xieyisheng1@huawei.com (Yisheng Xie)
Date: Thu, 30 Nov 2017 10:45:36 +0800
Subject: [RFCv2 PATCH 09/36] iommu/fault: Allow blocking fault handlers
In-Reply-To: <74891e35-17d8-5831-1ebd-18e00ce00d74@arm.com>
References: <20171006133203.22803-1-jean-philippe.brucker@arm.com>
 <20171006133203.22803-10-jean-philippe.brucker@arm.com>
 <7e1c8ea4-e568-1000-17de-62f8562c7169@huawei.com>
 <74891e35-17d8-5831-1ebd-18e00ce00d74@arm.com>
Message-ID: <3156bbca-e588-5c57-6df6-05bf9c25c747@huawei.com>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

hi jean,

On 2017/11/29 23:01, Jean-Philippe Brucker wrote:
> Hello,
> 
> On 29/11/17 06:15, Yisheng Xie wrote:
>> Hi Jean,
>>
>> On 2017/10/6 21:31, Jean-Philippe Brucker wrote:
>>> -	if (domain->ext_handler) {
>>> +	if (domain->handler_flags & IOMMU_FAULT_HANDLER_ATOMIC) {
>>> +		fault->flags |= IOMMU_FAULT_ATOMIC;
>>
>> Why remove the condition of domain->ext_handler? should it be much better like:
>>   if ((domain->handler_flags & IOMMU_FAULT_HANDLER_ATOMIC) && domain->ext_handler)
>>
>> If domain->ext_handler is NULL, and (domain->handler_flags & IOMMU_FAULT_HANDLER_ATOMIC)
>> is true. It will oops, right?
> 
> I removed the check because ext_handler shouldn't be NULL if handler_flags
> has a bit set (as per iommu_set_ext_fault_handler). But you're right that
> this is fragile, and I overlooked the case where users could call
> set_ext_fault_handler to clear the fault handler.
> 
> (Note that this ext_handler will most likely be replaced by the fault
> infrastructure that Jacob is working on:
> https://patchwork.kernel.org/patch/10063385/ to which we should add the
> atomic/blocking flags)
> 

Get it, thanks for your explanation.

Thanks
Yisheng Xie

> Thanks,
> Jean
> 
> .
>