linux-kernel - Re: [PATCH v1 5/8] iommu/amd: Use iommu_attach/detach

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Message-ID: <456972f1-0237-81db-69cf-363f9ac611e0@linux.intel.com>
Date:   Fri, 7 Jan 2022 08:23:05 +0800
From:   Lu Baolu <baolu.lu@...ux.intel.com>
To:     Jason Gunthorpe <jgg@...dia.com>
Cc:     baolu.lu@...ux.intel.com, Joerg Roedel <joro@...tes.org>,
        Alex Williamson <alex.williamson@...hat.com>,
        Robin Murphy <robin.murphy@....com>,
        Christoph Hellwig <hch@...radead.org>,
        Kevin Tian <kevin.tian@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Will Deacon <will@...nel.org>,
        Dan Williams <dan.j.williams@...el.com>, rafael@...nel.org,
        Diana Craciun <diana.craciun@....nxp.com>,
        Cornelia Huck <cohuck@...hat.com>,
        Eric Auger <eric.auger@...hat.com>,
        Liu Yi L <yi.l.liu@...el.com>,
        Jacob jun Pan <jacob.jun.pan@...el.com>,
        Chaitanya Kulkarni <kch@...dia.com>,
        Stuart Yoder <stuyoder@...il.com>,
        Laurentiu Tudor <laurentiu.tudor@....com>,
        Thierry Reding <thierry.reding@...il.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Li Yang <leoyang.li@....com>,
        Dmitry Osipenko <digetx@...il.com>,
        iommu@...ts.linux-foundation.org, linux-pci@...r.kernel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 5/8] iommu/amd: Use iommu_attach/detach_device()

Hi Jason,

On 1/6/22 10:33 PM, Jason Gunthorpe wrote:
> On Thu, Jan 06, 2022 at 10:20:50AM +0800, Lu Baolu wrote:
>> The individual device driver should use iommu_attach/detach_device()
>> for domain attachment/detachment.
>>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>>   drivers/iommu/amd/iommu_v2.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/iommu/amd/iommu_v2.c b/drivers/iommu/amd/iommu_v2.c
>> index 58da08cc3d01..7d9d0fe89064 100644
>> +++ b/drivers/iommu/amd/iommu_v2.c
>> @@ -133,7 +133,7 @@ static void free_device_state(struct device_state *dev_state)
>>   	if (WARN_ON(!group))
>>   		return;
>>   
>> -	iommu_detach_group(dev_state->domain, group);
>> +	iommu_detach_device(dev_state->domain, &dev_state->pdev->dev);
>>   
>>   	iommu_group_put(group);
> 
> This is the only user of the group in the function all the
> group_get/put should be deleted too.
> 
> Joerg said in commit 55c99a4dc50f ("iommu/amd: Use
> iommu_attach_group()") that the device API doesn't work here because
> there are multi-device groups?
> 
> But I'm not sure how this can work with multi-device groups - this
> seems to assigns a domain setup for direct map, so perhaps this only
> works if all devices are setup for direct map?

It's also difficult for me to understand how this can work with multi-
device group. The iommu_attach_group() returns -EBUSY if _init_device()
is called for the second device in the group. That's the reason why I
didn't set no_kernel_dma.

> 
>> @@ -791,7 +791,7 @@ int amd_iommu_init_device(struct pci_dev *pdev, int pasids)
>>   		goto out_free_domain;
>>   	}
>>   
>> -	ret = iommu_attach_group(dev_state->domain, group);
>> +	ret = iommu_attach_device(dev_state->domain, &pdev->dev);
>>   	if (ret != 0)
>>   		goto out_drop_group;
> 
> Same comment here

Yes.

> 
> Jason
> 

Best regards,
baolu