linux-kernel - Re: [PATCH v13 1/6] iommu: Deprecate Intel and AMD cmdline methods to enable strict mode

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Date:   Fri, 18 Jun 2021 08:43:32 +0100
From:   John Garry <john.garry@...wei.com>
To:     Robin Murphy <robin.murphy@....com>, <joro@...tes.org>,
        <will@...nel.org>, <dwmw2@...radead.org>,
        <baolu.lu@...ux.intel.com>, <corbet@....net>
CC:     <linux-kernel@...r.kernel.org>, <iommu@...ts.linux-foundation.org>,
        <linuxarm@...wei.com>, <thunder.leizhen@...wei.com>,
        <chenxiang66@...ilicon.com>, <linux-doc@...r.kernel.org>
Subject: Re: [PATCH v13 1/6] iommu: Deprecate Intel and AMD cmdline methods to
 enable strict mode

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@....com>

Cheers!