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From: John Garry <john.garry@huawei.com>
To: Lu Baolu <baolu.lu@linux.intel.com>, <joro@8bytes.org>,
	<will@kernel.org>, <dwmw2@infradead.org>, <robin.murphy@arm.com>,
	<corbet@lwn.net>
Cc: <linux-kernel@vger.kernel.org>,
	<iommu@lists.linux-foundation.org>, <linuxarm@huawei.com>,
	<thunder.leizhen@huawei.com>, <chenxiang66@hisilicon.com>,
	<linux-doc@vger.kernel.org>
Subject: Re: [PATCH v13 6/6] iommu: Remove mode argument from iommu_set_dma_strict()
Date: Thu, 17 Jun 2021 08:41:24 +0100	[thread overview]
Message-ID: <c61376c8-5285-1121-046f-3ab12eee9902@huawei.com> (raw)
In-Reply-To: <de6a2874-3d6d-ed2a-78f5-fb1fb0195228@linux.intel.com>


>> @@ -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);
> 
>          if (!ret)
>                  iommu_cmd_line |= IOMMU_CMD_LINE_STRICT;
>          return ret;
> }
> early_param("iommu.strict", iommu_dma_setup);
> 
> The bit IOMMU_CMD_LINE_STRICT is only set, but not used anywhere.

It is used in patch 2/6:

+	pr_info("DMA domain TLB invalidation policy: %s mode %s\n",
+		iommu_dma_strict ? "strict" : "lazy",
+		(iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
+			"(set via kernel command line)" : "");

> Hence,
> I am wondering how could it work? A bug or I missed anything?

It is really just used for informative purpose now.

Thanks,
john

WARNING: multiple messages have this Message-ID (diff)
From: John Garry <john.garry@huawei.com>
To: Lu Baolu <baolu.lu@linux.intel.com>, <joro@8bytes.org>,
	<will@kernel.org>,  <dwmw2@infradead.org>, <robin.murphy@arm.com>,
	<corbet@lwn.net>
Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	linuxarm@huawei.com, iommu@lists.linux-foundation.org
Subject: Re: [PATCH v13 6/6] iommu: Remove mode argument from iommu_set_dma_strict()
Date: Thu, 17 Jun 2021 08:41:24 +0100	[thread overview]
Message-ID: <c61376c8-5285-1121-046f-3ab12eee9902@huawei.com> (raw)
In-Reply-To: <de6a2874-3d6d-ed2a-78f5-fb1fb0195228@linux.intel.com>


>> @@ -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);
> 
>          if (!ret)
>                  iommu_cmd_line |= IOMMU_CMD_LINE_STRICT;
>          return ret;
> }
> early_param("iommu.strict", iommu_dma_setup);
> 
> The bit IOMMU_CMD_LINE_STRICT is only set, but not used anywhere.

It is used in patch 2/6:

+	pr_info("DMA domain TLB invalidation policy: %s mode %s\n",
+		iommu_dma_strict ? "strict" : "lazy",
+		(iommu_cmd_line & IOMMU_CMD_LINE_STRICT) ?
+			"(set via kernel command line)" : "");

> Hence,
> I am wondering how could it work? A bug or I missed anything?

It is really just used for informative purpose now.

Thanks,
john
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu

  reply	other threads:[~2021-06-17  7:47 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-16 11:03 [PATCH v13 0/6] iommu: Enhance IOMMU default DMA mode build options John Garry
2021-06-16 11:03 ` John Garry
2021-06-16 11:03 ` [PATCH v13 1/6] iommu: Deprecate Intel and AMD cmdline methods to enable strict mode John Garry
2021-06-16 11:03   ` John Garry
2021-06-17 19:01   ` Robin Murphy
2021-06-17 19:01     ` Robin Murphy
2021-06-18  7:43     ` John Garry
2021-06-18  7:43       ` John Garry
2021-06-16 11:03 ` [PATCH v13 2/6] iommu: Print strict or lazy mode at init time John Garry
2021-06-16 11:03   ` John Garry
2021-06-16 11:03 ` [PATCH v13 3/6] iommu: Enhance IOMMU default DMA mode build options John Garry
2021-06-16 11:03   ` John Garry
2021-06-16 11:03 ` [PATCH v13 4/6] iommu/vt-d: Add support for " John Garry
2021-06-16 11:03   ` John Garry
2021-06-17  7:32   ` Lu Baolu
2021-06-17  7:32     ` Lu Baolu
2021-06-17  8:00     ` John Garry
2021-06-17  8:00       ` John Garry
2021-06-17 19:03       ` Robin Murphy
2021-06-17 19:03         ` Robin Murphy
2021-06-18  1:46       ` Lu Baolu
2021-06-18  1:46         ` Lu Baolu
2021-06-18  7:31         ` John Garry
2021-06-18  7:31           ` John Garry
2021-06-16 11:03 ` [PATCH v13 5/6] iommu/amd: " John Garry
2021-06-16 11:03   ` John Garry
2021-06-16 11:03 ` [PATCH v13 6/6] iommu: Remove mode argument from iommu_set_dma_strict() John Garry
2021-06-16 11:03   ` John Garry
2021-06-17  7:36   ` Lu Baolu
2021-06-17  7:36     ` Lu Baolu
2021-06-17  7:41     ` John Garry [this message]
2021-06-17  7:41       ` John Garry
2021-06-18  1:52       ` Lu Baolu
2021-06-18  1:52         ` Lu Baolu
2021-06-17 18:56     ` Robin Murphy
2021-06-17 18:56       ` Robin Murphy
2021-06-18  1:51       ` Lu Baolu
2021-06-18  1:51         ` Lu Baolu

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