linux-kernel - Re: [PATCH v7 08/10] iommu/dma-reserved_iommu: iommu_msi_mapping_desc_to

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Date:	Thu, 21 Apr 2016 10:40:38 +0200
From:	Eric Auger <eric.auger@...aro.org>
To:	Robin Murphy <robin.murphy@....com>, eric.auger@...com,
	alex.williamson@...hat.com, will.deacon@....com, joro@...tes.org,
	tglx@...utronix.de, jason@...edaemon.net, marc.zyngier@....com,
	christoffer.dall@...aro.org, linux-arm-kernel@...ts.infradead.org
Cc:	patches@...aro.org, linux-kernel@...r.kernel.org,
	Bharat.Bhushan@...escale.com, pranav.sawargaonkar@...il.com,
	p.fedin@...sung.com, iommu@...ts.linux-foundation.org,
	Jean-Philippe.Brucker@....com, julien.grall@....com
Subject: Re: [PATCH v7 08/10] iommu/dma-reserved_iommu:
 iommu_msi_mapping_desc_to_domain

Hi Robin,
On 04/20/2016 07:19 PM, Robin Murphy wrote:
> On 19/04/16 17:56, Eric Auger wrote:
>> This function checks whether
>> - the device emitting the MSI belongs to a non default iommu domain
>> - the iommu domain requires the MSI address to be mapped.
>>
>> If those conditions are met, the function returns the iommu domain
>> to be used for mapping the MSI doorbell; else it returns NULL.
>>
>> Signed-off-by: Eric Auger <eric.auger@...aro.org>
>> ---
>>   drivers/iommu/dma-reserved-iommu.c | 19 +++++++++++++++++++
>>   include/linux/dma-reserved-iommu.h | 18 ++++++++++++++++++
>>   2 files changed, 37 insertions(+)
>>
>> diff --git a/drivers/iommu/dma-reserved-iommu.c
>> b/drivers/iommu/dma-reserved-iommu.c
>> index 2522235..907a17f 100644
>> --- a/drivers/iommu/dma-reserved-iommu.c
>> +++ b/drivers/iommu/dma-reserved-iommu.c
>> @@ -17,6 +17,7 @@
>>
>>   #include <linux/iommu.h>
>>   #include <linux/iova.h>
>> +#include <linux/msi.h>
>>
>>   struct reserved_iova_domain {
>>       struct iova_domain *iovad;
>> @@ -332,3 +333,21 @@ unlock:
>>   }
>>   EXPORT_SYMBOL_GPL(iommu_put_reserved_iova);
>>
>> +struct iommu_domain *iommu_msi_mapping_desc_to_domain(struct msi_desc
>> *desc)
>> +{
>> +    struct device *dev;
>> +    struct iommu_domain *d;
>> +
>> +    dev = msi_desc_to_dev(desc);
>> +
>> +    d = iommu_get_domain_for_dev(dev);
>> +
>> +    if (!d || (d->type == IOMMU_DOMAIN_DMA))
>> +        return NULL;
>> +
>> +    if (iommu_domain_get_attr(d, DOMAIN_ATTR_MSI_MAPPING, NULL))
>> +        return NULL;
> 
> Yeah, I don't see why we couldn't just use
> 
> if (domain->ops->capable(IOMMU_CAP_INTR_REMAP))
>     return NULL
I don't think this works. This will lead to MSI iommu mapping on x86
when irq_remapping is disabled. To be further checked though.

Eric
> 
> there instead.
> 
>> +
>> +    return d;
>> +}
>> +EXPORT_SYMBOL_GPL(iommu_msi_mapping_desc_to_domain);
>> diff --git a/include/linux/dma-reserved-iommu.h
>> b/include/linux/dma-reserved-iommu.h
>> index 8722131..8373929 100644
>> --- a/include/linux/dma-reserved-iommu.h
>> +++ b/include/linux/dma-reserved-iommu.h
>> @@ -19,6 +19,7 @@
>>   #include <linux/kernel.h>
>>
>>   struct iommu_domain;
>> +struct msi_desc;
>>
>>   #ifdef CONFIG_IOMMU_DMA_RESERVED
>>
>> @@ -70,6 +71,17 @@ int iommu_get_reserved_iova(struct iommu_domain
>> *domain,
>>    * if the binding ref count is null, destroy the reserved mapping
>>    */
>>   void iommu_put_reserved_iova(struct iommu_domain *domain,
>> phys_addr_t addr);
>> +
>> +/**
>> + * iommu_msi_mapping_desc_to_domain: in case the MSI originates from
>> a device
>> + * upstream to an IOMMU and this IOMMU translates the MSI transaction,
>> + * this function returns the iommu domain the MSI doorbell address
>> must be
>> + * mapped in. Else it returns NULL.
>> + *
>> + * @desc: msi desc handle
>> + */
>> +struct iommu_domain *iommu_msi_mapping_desc_to_domain(struct msi_desc
>> *desc);
>> +
>>   #else
>>
>>   static inline int
>> @@ -93,5 +105,11 @@ static inline int iommu_get_reserved_iova(struct
>> iommu_domain *domain,
>>   static inline void iommu_put_reserved_iova(struct iommu_domain *domain,
>>                          phys_addr_t addr) {}
>>
>> +static inline struct iommu_domain *
>> +iommu_msi_mapping_desc_to_domain(struct msi_desc *desc)
>> +{
>> +    return NULL;
>> +}
>> +
>>   #endif    /* CONFIG_IOMMU_DMA_RESERVED */
>>   #endif    /* __DMA_RESERVED_IOMMU_H */
>>
>