linux-kernel - Re: [PATCH v4 10/19] iommu: Add set_platform_dma

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Date:   Thu, 5 Jan 2023 13:58:42 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Will Deacon <will@...nel.org>,
        Robin Murphy <robin.murphy@....com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Hector Martin <marcan@...can.st>,
        Sven Peter <sven@...npeter.dev>,
        Rob Clark <robdclark@...il.com>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Yong Wu <yong.wu@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Heiko Stuebner <heiko@...ech.de>,
        Matthew Rosato <mjrosato@...ux.ibm.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang@...ux.alibaba.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Chen-Yu Tsai <wens@...e.org>,
        Thierry Reding <thierry.reding@...il.com>,
        iommu@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 10/19] iommu: Add set_platform_dma_ops iommu ops

Hi Jason,

On 2023/1/4 21:17, Jason Gunthorpe wrote:
> On Wed, Jan 04, 2023 at 08:57:16PM +0800, Lu Baolu wrote:
> 
>> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
>> index de91dd88705b..4e35a9f94873 100644
>> --- a/drivers/iommu/iommu.c
>> +++ b/drivers/iommu/iommu.c
>> @@ -2163,6 +2163,17 @@ static int iommu_group_do_detach_device(struct device *dev, void *data)
>>   	return 0;
>>   }
>>   
>> +static int iommu_group_do_set_platform_dma(struct device *dev, void *data)
>> +{
>> +	const struct iommu_ops *ops = dev_iommu_ops(dev);
>> +
>> +	if (!ops->set_platform_dma_ops)
>> +		return -EINVAL;
>> +
>> +	ops->set_platform_dma_ops(dev);
>> +	return 0;
>> +}
>> +
>>   static int __iommu_group_set_domain(struct iommu_group *group,
>>   				    struct iommu_domain *new_domain)
>>   {
>> @@ -2177,10 +2188,14 @@ static int __iommu_group_set_domain(struct iommu_group *group,
>>   	 * platform specific behavior.
>>   	 */
>>   	if (!new_domain) {
>> -		if (WARN_ON(!group->domain->ops->detach_dev))
>> -			return -EINVAL;
> This should still have the WARN_ON..
> 
> if (WARN_ON(!group->domain->ops->detach_dev && !dev_iommu_ops(dev)->set_platform_dma_ops)

This has been implicitly included in the code.

iommu_group_do_set_platform_dma() returns -EINVAL if the iommu driver
doesn't support set_platform_dma_ops (otherwise always return success).
Then, the domain->ops->detach_dev is required and a WARN_ON was there.

         if (!new_domain) {
                 ret = __iommu_group_for_each_dev(group, NULL,
                                 iommu_group_do_set_platform_dma);
                 if (ret) {
                         if (WARN_ON(!group->domain->ops->detach_dev))
                                 return -EINVAL;
                         __iommu_group_for_each_dev(group, group->domain,
                                 iommu_group_do_detach_device);
                 }
                 group->domain = NULL;
                 return 0;
         }

Perhaps I should add a comment to explain this?

--
Best regards,
baolu