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Subject: Re: [PATCH v13 1/6] iommu: Deprecate Intel and AMD cmdline methods to
 enable strict mode
To:     Robin Murphy <robin.murphy@arm.com>, <joro@8bytes.org>,
        <will@kernel.org>, <dwmw2@infradead.org>,
        <baolu.lu@linux.intel.com>, <corbet@lwn.net>
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From:   John Garry <john.garry@huawei.com>
Message-ID: <c8ca952e-4070-0a48-0a77-1cdf6985bb19@huawei.com>
Date:   Fri, 18 Jun 2021 08:43:32 +0100
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On 17/06/2021 20:01, Robin Murphy wrote:
>>               DMA.
>> -        strict [Default Off]
>> +        strict [Default Off] [Deprecated, use iommu.strict instead]
>>               With this option on every unmap_single operation will
>>               result in a hardware IOTLB flush operation as opposed
>>               to batching them for performance.
> 
> FWIW I'd be inclined to replace both whole descriptions with just 
> something like "Deprecated, equivalent to iommu.strict=1".
> 
>> diff --git a/drivers/iommu/amd/init.c b/drivers/iommu/amd/init.c
>> index 46280e6e1535..9f3096d650aa 100644
>> --- a/drivers/iommu/amd/init.c
>> +++ b/drivers/iommu/amd/init.c
>> @@ -3098,8 +3098,10 @@ static int __init parse_amd_iommu_intr(char *str)
>>   static int __init parse_amd_iommu_options(char *str)
>>   {
>>       for (; *str; ++str) {
>> -        if (strncmp(str, "fullflush", 9) == 0)
>> +        if (strncmp(str, "fullflush", 9) == 0) {
>> +            pr_warn("amd_iommu=fullflush deprecated; use iommu.strict 
>> instead\n");
> 
> Nit: maybe we should spell out "...use <option>=1 instead" in all of 
> these messages just in case anyone takes them literally?


> (I'm not sure 
> the options parse correctly with no argument)

I don't think they do.

But I'll take both suggestions on board.

> 
> Either way,
> 
> Acked-by: Robin Murphy <robin.murphy@arm.com>

Cheers!