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Message-ID: <e4493dac-07bf-7ee3-5bea-a159fd37a2dd@linux.intel.com>
Date: Tue, 25 Jan 2022 11:18:01 +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>,
Christoph Hellwig <hch@...radead.org>,
Ben Skeggs <bskeggs@...hat.com>,
Kevin Tian <kevin.tian@...el.com>,
Ashok Raj <ashok.raj@...el.com>, Will Deacon <will@...nel.org>,
Robin Murphy <robin.murphy@....com>,
Alex Williamson <alex.williamson@...hat.com>,
Eric Auger <eric.auger@...hat.com>,
Liu Yi L <yi.l.liu@...el.com>,
Jacob jun Pan <jacob.jun.pan@...el.com>,
David Airlie <airlied@...ux.ie>,
Daniel Vetter <daniel@...ll.ch>,
Thierry Reding <thierry.reding@...il.com>,
Jonathan Hunter <jonathanh@...dia.com>,
iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/7] iommu: Use right way to retrieve iommu_ops
On 1/25/22 1:36 AM, Jason Gunthorpe wrote:
> On Mon, Jan 24, 2022 at 03:11:01PM +0800, Lu Baolu wrote:
>> The common iommu_ops is hooked to both device and domain. When a helper
>> has both device and domain pointer, the way to get the iommu_ops looks
>> messy in iommu core. This sorts out the way to get iommu_ops. The device
>> related helpers go through device pointer, while the domain related ones
>> go through domain pointer.
>>
>> Signed-off-by: Lu Baolu <baolu.lu@...ux.intel.com>
>> include/linux/iommu.h | 8 ++++++++
>> drivers/iommu/iommu.c | 25 ++++++++++++++-----------
>> 2 files changed, 22 insertions(+), 11 deletions(-)
>>
>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>> index aa5486243892..111b3e9c79bb 100644
>> +++ b/include/linux/iommu.h
>> @@ -385,6 +385,14 @@ static inline void iommu_iotlb_gather_init(struct iommu_iotlb_gather *gather)
>> };
>> }
>>
>> +static inline const struct iommu_ops *dev_iommu_ops_get(struct device *dev)
>> +{
>> + if (dev && dev->iommu && dev->iommu->iommu_dev)
>> + return dev->iommu->iommu_dev->ops;
>> +
>> + return NULL;
>
> What is the purpose of this helper?
Get the iommu_ops from a device pointer. Just want to avoid duplicate
code in various functions.
>
>> + const struct iommu_ops *ops = dev_iommu_ops_get(dev);
>> struct iommu_domain *domain = group->default_domain;
>> struct iommu_resv_region *entry;
>> struct list_head mappings;
>> @@ -785,8 +786,8 @@ static int iommu_create_device_direct_mappings(struct iommu_group *group,
>> dma_addr_t start, end, addr;
>> size_t map_size = 0;
>>
>> - if (domain->ops->apply_resv_region)
>> - domain->ops->apply_resv_region(dev, domain, entry);
>> + if (ops->apply_resv_region)
>> + ops->apply_resv_region(dev, domain, entry);
>
> Here we call it and don't check for NULL? So why did we check the
> interior pointers in the helper?
Yes. Should check.
>
>> @@ -831,8 +832,10 @@ static int iommu_create_device_direct_mappings(struct iommu_group *group,
>> static bool iommu_is_attach_deferred(struct iommu_domain *domain,
>> struct device *dev)
>> {
>> - if (domain->ops->is_attach_deferred)
>> - return domain->ops->is_attach_deferred(domain, dev);
>> + const struct iommu_ops *ops = dev_iommu_ops_get(dev);
>> +
>> + if (ops->is_attach_deferred)
>> + return ops->is_attach_deferred(domain, dev);
>
> Same here, at least return false if ops is null..
Yes.
>
>> @@ -1251,10 +1254,10 @@ int iommu_page_response(struct device *dev,
>> struct iommu_fault_event *evt;
>> struct iommu_fault_page_request *prm;
>> struct dev_iommu *param = dev->iommu;
>> + const struct iommu_ops *ops = dev_iommu_ops_get(dev);
>> bool has_pasid = msg->flags & IOMMU_PAGE_RESP_PASID_VALID;
>> - struct iommu_domain *domain = iommu_get_domain_for_dev(dev);
>>
>> - if (!domain || !domain->ops->page_response)
>> + if (!ops || !ops->page_response)
>> return -ENODEV;
>>
>> if (!param || !param->fault_param)
>> @@ -1295,7 +1298,7 @@ int iommu_page_response(struct device *dev,
>> msg->pasid = 0;
>> }
>>
>> - ret = domain->ops->page_response(dev, evt, msg);
>> + ret = ops->page_response(dev, evt, msg);
>> list_del(&evt->list);
>> kfree(evt);
>> break;
>
> Feels weird that page_response is not connected to a domain, the fault
> originated from a domain after all. I would say this op should be
> moved to the domain and the caller should provide the a pointer to the
> domain that originated the fault.
>
> Ideally since only some domain's will be configured to handle faults
> at all - domains that can't do this should have a NULL page_response
> op, even if other domains created by the same device driver could
> handle page_response..
>
>> @@ -1758,10 +1761,10 @@ static int __iommu_group_dma_attach(struct iommu_group *group)
>>
>> static int iommu_group_do_probe_finalize(struct device *dev, void *data)
>> {
>> - struct iommu_domain *domain = data;
>> + const struct iommu_ops *ops = dev_iommu_ops_get(dev);
>>
>> - if (domain->ops->probe_finalize)
>> - domain->ops->probe_finalize(dev);
>> + if (ops->probe_finalize)
>> + ops->probe_finalize(dev);
>
> This is an oddball one too, it is finishing setting up the default
> domain for a device? Several drivers seem to recover the default
> domain in their implementations..
In order to avoid default domain type (DMA or IDENDITY) conflict among
devices in a same iommu_group, the probe process is divided into two
phases, one for determining the default domain type and the other for
allocating the default domain and attaching it to the device.
ops->probe_finalize() is called to tell the vendor iommu driver that
the device probe is done. Normally the vendor iommu driver could set the
dma ops in this callback.
>
> Jason
>
Best regards,
baolu
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