linux-kernel - Re: [PATCH v3 02/20] iommu/apple-dart: Remove detach

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Date:   Thu, 1 Dec 2022 12:50:52 +0800
From:   Baolu Lu <baolu.lu@...ux.intel.com>
To:     Sven Peter <sven@...npeter.dev>, Joerg Roedel <joro@...tes.org>,
        Jason Gunthorpe <jgg@...dia.com>,
        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>
Cc:     baolu.lu@...ux.intel.com,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>,
        Hector Martin <marcan@...can.st>,
        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 v3 02/20] iommu/apple-dart: Remove detach_dev callback

On 2022/12/1 1:00, Sven Peter wrote:
> On Mon, Nov 28, 2022, at 07:46, Lu Baolu wrote:
>> The IOMMU driver supports default domain, so the detach_dev op will never
>> be called. Remove it to avoid dead code.
>>
>> Signed-off-by: Lu Baolu<baolu.lu@...ux.intel.com>
>> ---
> Reviewed-by: Sven Peter<sven@...npeter.dev>
> 
>>   drivers/iommu/apple-dart.c | 17 -----------------
>>   1 file changed, 17 deletions(-)
>>
>> diff --git a/drivers/iommu/apple-dart.c b/drivers/iommu/apple-dart.c
>> index 4f4a323be0d0..6fbe6b275c79 100644
>> --- a/drivers/iommu/apple-dart.c
>> +++ b/drivers/iommu/apple-dart.c
>> @@ -535,22 +535,6 @@ static int apple_dart_attach_dev(struct
>> iommu_domain *domain,
>>   	return ret;
>>   }
>>
>> -static void apple_dart_detach_dev(struct iommu_domain *domain,
>> -				  struct device *dev)
>> -{
> Thanks for cleaning this entire API up!
> 
> It actually turns out that this is slightly broken because I assumed that
> detach_dev would always be called for any attach_dev. I think the only
> consequence for a device that used to be assigned to domain A and is now moved to
> domain B is that any TLB flushes required for A will still flush the TLB for that
> device.
> 
> That's not a big deal but I'll eventually send a fix.
> 
>> -	int i;
>> -	struct apple_dart_stream_map *stream_map;
>> -	struct apple_dart_master_cfg *cfg = dev_iommu_priv_get(dev);
>> -	struct apple_dart_domain *dart_domain = to_dart_domain(domain);
>> -
>> -	for_each_stream_map(i, cfg, stream_map)
>> -		apple_dart_hw_disable_dma(stream_map);
>> -
>> -	if (domain->type == IOMMU_DOMAIN_DMA ||
>> -	    domain->type == IOMMU_DOMAIN_UNMANAGED)
>> -		apple_dart_domain_remove_streams(dart_domain, cfg);
> Something might complain about unused apple_dart_domain_remove_streams now.
> Might make sense to drop that for now as well.

Done. Thanks!

Best regards,
baolu