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Cc:     baolu.lu@linux.intel.com, linux-kernel@vger.kernel.org,
        iommu@lists.linux-foundation.org, linuxarm@huawei.com,
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Subject: Re: [PATCH v13 6/6] iommu: Remove mode argument from
 iommu_set_dma_strict()
To:     Robin Murphy <robin.murphy@arm.com>,
        John Garry <john.garry@huawei.com>, joro@8bytes.org,
        will@kernel.org, dwmw2@infradead.org, corbet@lwn.net
References: <1623841437-211832-1-git-send-email-john.garry@huawei.com>
 <1623841437-211832-7-git-send-email-john.garry@huawei.com>
 <de6a2874-3d6d-ed2a-78f5-fb1fb0195228@linux.intel.com>
 <7d0fb0e2-4671-16db-6963-b0493d7a549b@arm.com>
From:   Lu Baolu <baolu.lu@linux.intel.com>
Message-ID: <b6484679-0950-8c8e-98c5-da0e4c1d97e2@linux.intel.com>
Date:   Fri, 18 Jun 2021 09:51:48 +0800
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Hi Robin,

On 6/18/21 2:56 AM, Robin Murphy wrote:
>>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>>> index 60b1ec42e73b..ff221d3ddcbc 100644
>>> --- a/drivers/iommu/iommu.c
>>> +++ b/drivers/iommu/iommu.c
>>> @@ -349,10 +349,9 @@ static int __init iommu_dma_setup(char *str)
>>>   }
>>>   early_param("iommu.strict", iommu_dma_setup);
>>> -void iommu_set_dma_strict(bool strict)
>>> +void iommu_set_dma_strict(void)
>>>   {
>>> -    if (strict || !(iommu_cmd_line & IOMMU_CMD_LINE_STRICT))
>>> -        iommu_dma_strict = strict;
>>> +    iommu_dma_strict = true;
>>
>> Sorry, I still can't get how iommu.strict kernel option works.
>>
>> static int __init iommu_dma_setup(char *str)
>> {
>>          int ret = kstrtobool(str, &iommu_dma_strict);
> 
> Note that this is the bit that does the real work - if the argument 
> parses OK then iommu_dma_strict is reassigned with the appropriate 
> value. The iommu_cmd_line stuff is a bit of additional bookkeeping, 
> basically just so we can see whether default values have been overridden.

Ah, get it. Thanks a lot. I missed this part and naively thought it just
converts a string to integer.

Best regards,
baolu