Re: [PATCH 5/7] iommu/dma: add support for non-strict mode

["Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>]

On 2018/5/31 21:04, Robin Murphy wrote:
> On 31/05/18 08:42, Zhen Lei wrote:
>> 1. Save the related domain pointer in struct iommu_dma_cookie, make iovad
>>     capable call domain->ops->flush_iotlb_all to flush TLB.
>> 2. Define a new iommu capable: IOMMU_CAP_NON_STRICT, which used to indicate
>>     that the iommu domain support non-strict mode.
>> 3. During the iommu domain initialization phase, call capable() to check
>>     whether it support non-strcit mode. If so, call init_iova_flush_queue
>>     to register iovad->flush_cb callback.
>> 4. All unmap(contains iova-free) APIs will finally invoke __iommu_dma_unmap
>>     -->iommu_dma_free_iova. Use iovad->flush_cb to check whether its related
>>     iommu support non-strict mode or not, and call IOMMU_DOMAIN_IS_STRICT to
>>     make sure the IOMMU_DOMAIN_UNMANAGED domain always follow strict mode.
> 
> Once again, this is a whole load of complexity for a property which could just be statically encoded at allocation, e.g. in the cookie type.
That's right. Pass domain to the static function iommu_dma_free_iova will be better.

> 
>> Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
>> ---
>>   drivers/iommu/dma-iommu.c | 29 ++++++++++++++++++++++++++---
>>   include/linux/iommu.h     |  3 +++
>>   2 files changed, 29 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>> index 4e885f7..2e116d9 100644
>> --- a/drivers/iommu/dma-iommu.c
>> +++ b/drivers/iommu/dma-iommu.c
>> @@ -55,6 +55,7 @@ struct iommu_dma_cookie {
>>       };
>>       struct list_head        msi_page_list;
>>       spinlock_t            msi_lock;
>> +    struct iommu_domain        *domain;
>>   };
>>     static inline size_t cookie_msi_granule(struct iommu_dma_cookie *cookie)
>> @@ -64,7 +65,8 @@ static inline size_t cookie_msi_granule(struct iommu_dma_cookie *cookie)
>>       return PAGE_SIZE;
>>   }
>>   -static struct iommu_dma_cookie *cookie_alloc(enum iommu_dma_cookie_type type)
>> +static struct iommu_dma_cookie *cookie_alloc(struct iommu_domain *domain,
>> +                         enum iommu_dma_cookie_type type)
>>   {
>>       struct iommu_dma_cookie *cookie;
>>   @@ -73,6 +75,7 @@ static struct iommu_dma_cookie *cookie_alloc(enum iommu_dma_cookie_type type)
>>           spin_lock_init(&cookie->msi_lock);
>>           INIT_LIST_HEAD(&cookie->msi_page_list);
>>           cookie->type = type;
>> +        cookie->domain = domain;
>>       }
>>       return cookie;
>>   }
>> @@ -94,7 +97,7 @@ int iommu_get_dma_cookie(struct iommu_domain *domain)
>>       if (domain->iova_cookie)
>>           return -EEXIST;
>>   -    domain->iova_cookie = cookie_alloc(IOMMU_DMA_IOVA_COOKIE);
>> +    domain->iova_cookie = cookie_alloc(domain, IOMMU_DMA_IOVA_COOKIE);
>>       if (!domain->iova_cookie)
>>           return -ENOMEM;
>>   @@ -124,7 +127,7 @@ int iommu_get_msi_cookie(struct iommu_domain *domain, dma_addr_t base)
>>       if (domain->iova_cookie)
>>           return -EEXIST;
>>   -    cookie = cookie_alloc(IOMMU_DMA_MSI_COOKIE);
>> +    cookie = cookie_alloc(domain, IOMMU_DMA_MSI_COOKIE);
>>       if (!cookie)
>>           return -ENOMEM;
>>   @@ -261,6 +264,17 @@ static int iova_reserve_iommu_regions(struct device *dev,
>>       return ret;
>>   }
>>   +static void iova_flush_iotlb_all(struct iova_domain *iovad)
> 
> iommu_dma_flush...
OK

> 
>> +{
>> +    struct iommu_dma_cookie *cookie;
>> +    struct iommu_domain *domain;
>> +
>> +    cookie = container_of(iovad, struct iommu_dma_cookie, iovad);
>> +    domain = cookie->domain;
>> +
>> +    domain->ops->flush_iotlb_all(domain);
>> +}
>> +
>>   /**
>>    * iommu_dma_init_domain - Initialise a DMA mapping domain
>>    * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie()
>> @@ -276,6 +290,7 @@ static int iova_reserve_iommu_regions(struct device *dev,
>>   int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
>>           u64 size, struct device *dev)
>>   {
>> +    const struct iommu_ops *ops = domain->ops;
>>       struct iommu_dma_cookie *cookie = domain->iova_cookie;
>>       struct iova_domain *iovad = &cookie->iovad;
>>       unsigned long order, base_pfn, end_pfn;
>> @@ -313,6 +328,11 @@ int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base,
>>         init_iova_domain(iovad, 1UL << order, base_pfn);
>>   +    if (ops->capable && ops->capable(IOMMU_CAP_NON_STRICT)) {
>> +        BUG_ON(!ops->flush_iotlb_all);
>> +        init_iova_flush_queue(iovad, iova_flush_iotlb_all, NULL);
>> +    }
>> +
>>       return iova_reserve_iommu_regions(dev, domain);
>>   }
>>   EXPORT_SYMBOL(iommu_dma_init_domain);
>> @@ -392,6 +412,9 @@ static void iommu_dma_free_iova(struct iommu_dma_cookie *cookie,
>>       /* The MSI case is only ever cleaning up its most recent allocation */
>>       if (cookie->type == IOMMU_DMA_MSI_COOKIE)
>>           cookie->msi_iova -= size;
>> +    else if (!IOMMU_DOMAIN_IS_STRICT(cookie->domain) && iovad->flush_cb)
>> +        queue_iova(iovad, iova_pfn(iovad, iova),
>> +                size >> iova_shift(iovad), 0);
>>       else
>>           free_iova_fast(iovad, iova_pfn(iovad, iova),
>>                   size >> iova_shift(iovad));
>> diff --git a/include/linux/iommu.h b/include/linux/iommu.h
>> index 39b3150..01ff569 100644
>> --- a/include/linux/iommu.h
>> +++ b/include/linux/iommu.h
>> @@ -87,6 +87,8 @@ struct iommu_domain_geometry {
>>                    __IOMMU_DOMAIN_DMA_API)
>>     #define IOMMU_STRICT        1
>> +#define IOMMU_DOMAIN_IS_STRICT(domain)    \
>> +        (domain->type == IOMMU_DOMAIN_UNMANAGED)
>>     struct iommu_domain {
>>       unsigned type;
>> @@ -103,6 +105,7 @@ enum iommu_cap {
>>                          transactions */
>>       IOMMU_CAP_INTR_REMAP,        /* IOMMU supports interrupt isolation */
>>       IOMMU_CAP_NOEXEC,        /* IOMMU_NOEXEC flag */
>> +    IOMMU_CAP_NON_STRICT,        /* IOMMU supports non-strict mode */
> 
> This isn't a property of the IOMMU, it depends purely on the driver implementation. I think it also doesn't matter anyway - if a caller asks for lazy unmapping on their domain but the IOMMU driver just does strict unmaps anyway because that's all it supports, there's no actual harm done.
> 
> Robin.
> 
>>   };
>>     /*
>>
> 
> .
> 

-- 
Thanks!
BestRegards