linux-kernel - Re: [PATCH v3 03/15] iommu: Always register bus notifiers

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Date:   Thu, 7 Jul 2022 08:20:32 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Robin Murphy <robin.murphy@....com>, joro@...tes.org
Cc:     baolu.lu@...ux.intel.com, will@...nel.org, iommu@...ts.linux.dev,
        linux-arm-kernel@...ts.infradead.org,
        suravee.suthikulpanit@....com, vasant.hegde@....com,
        mjrosato@...ux.ibm.com, gerald.schaefer@...ux.ibm.com,
        schnelle@...ux.ibm.com, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 03/15] iommu: Always register bus notifiers

On 2022/7/6 21:43, Robin Murphy wrote:
> On 2022-07-06 02:53, Baolu Lu wrote:
>> On 2022/7/6 01:08, Robin Murphy wrote:
>>>   /*
>>>    * Use a function instead of an array here because the domain-type 
>>> is a
>>>    * bit-field, so an array would waste memory.
>>> @@ -152,6 +172,10 @@ static int __init iommu_subsys_init(void)
>>>               (iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
>>>                   "(set via kernel command line)" : "");
>>> +    /* If the system is so broken that this fails, it will WARN 
>>> anyway */
>>
>> Can you please elaborate a bit on this? iommu_bus_init() still return
>> errors.
> 
> Indeed, it's commenting on the fact that we don't try to clean up or 
> propagate an error value further even if it did ever manage to return 
> one. I feared that if I strip the error handling out of iommu_bus_init() 
> itself on the same reasoning, we'll just get constant patches from the 
> static checker brigade trying to add it back, so it seemed like the 
> neatest compromise to keep that decision where it's obviously in an 
> early initcall, rather than in the helper function which can be viewed 
> out of context. However, I'm happy to either expand this comment or go 
> the whole way and make iommu_bus_init() return void if you think it's 
> worthwhile.

Thanks for the explanation. It would be helpful if the comment could be
expanded. In this case, after a long time, people will not consider it
an oversight. :-)

Best regards,
baolu

> 
> Cheers,
> Robin.
> 
>>
>>> +    for (int i = 0; i < ARRAY_SIZE(iommu_buses); i++)
>>> +        iommu_bus_init(iommu_buses[i]);
>>> +
>>>       return 0;
>>
>> Best regards,
>> baolu
>