Re: [PATCH v7 09/10] iommu/dma-reserved-iommu: iommu_msi_mapping_translate_msg

[Eric Auger]

On 04/20/2016 11:38 AM, Marc Zyngier wrote:
> On 19/04/16 17:56, Eric Auger wrote:
>> Introduce iommu_msi_mapping_translate_msg whose role consists in
>> detecting whether the device's MSIs must to be mapped into an IOMMU.
>> It case it must, the function overrides the MSI msg originally composed
>> and replaces the doorbell's PA by a pre-allocated and pre-mapped reserved
>> IOVA. In case the corresponding PA region is not found, the function
>> returns an error.
>>
>> This function is likely to be called in some code that cannot sleep. This
>> is the reason why the allocation/mapping is done separately.
>>
>> Signed-off-by: Eric Auger <eric.auger@xxxxxxxxxx>
>>
>> ---
>>
>> v7: creation
>> ---
>>  drivers/iommu/dma-reserved-iommu.c | 69 ++++++++++++++++++++++++++++++++++++++
>>  include/linux/dma-reserved-iommu.h | 27 +++++++++++++++
>>  2 files changed, 96 insertions(+)
>>
>> diff --git a/drivers/iommu/dma-reserved-iommu.c b/drivers/iommu/dma-reserved-iommu.c
>> index 907a17f..603ee45 100644
>> --- a/drivers/iommu/dma-reserved-iommu.c
>> +++ b/drivers/iommu/dma-reserved-iommu.c
>> @@ -18,6 +18,14 @@
>>  #include <linux/iommu.h>
>>  #include <linux/iova.h>
>>  #include <linux/msi.h>
>> +#include <linux/irq.h>
>> +
>> +#ifdef CONFIG_PHYS_ADDR_T_64BIT
>> +#define msg_to_phys_addr(msg) \
>> +	(((phys_addr_t)((msg)->address_hi) << 32) | (msg)->address_lo)
>> +#else
>> +#define msg_to_phys_addr(msg)	((msg)->address_lo)
>> +#endif
>>  
>>  struct reserved_iova_domain {
>>  	struct iova_domain *iovad;
>> @@ -351,3 +359,64 @@ struct iommu_domain *iommu_msi_mapping_desc_to_domain(struct msi_desc *desc)
>>  	return d;
>>  }
>>  EXPORT_SYMBOL_GPL(iommu_msi_mapping_desc_to_domain);
>> +
>> +static dma_addr_t iommu_find_reserved_iova(struct iommu_domain *domain,
>> +				    phys_addr_t addr, size_t size)
>> +{
>> +	unsigned long  base_pfn, end_pfn, nb_iommu_pages, order, flags;
>> +	size_t iommu_page_size, binding_size;
>> +	struct iommu_reserved_binding *b;
>> +	phys_addr_t aligned_base, offset;
>> +	dma_addr_t iova = DMA_ERROR_CODE;
>> +	struct iova_domain *iovad;
>> +
>> +	spin_lock_irqsave(&domain->reserved_lock, flags);
>> +
>> +	iovad = (struct iova_domain *)domain->reserved_iova_cookie;
>> +
>> +	if (!iovad)
>> +		goto unlock;
>> +
>> +	order = iova_shift(iovad);
>> +	base_pfn = addr >> order;
>> +	end_pfn = (addr + size - 1) >> order;
>> +	aligned_base = base_pfn << order;
>> +	offset = addr - aligned_base;
>> +	nb_iommu_pages = end_pfn - base_pfn + 1;
>> +	iommu_page_size = 1 << order;
>> +	binding_size = nb_iommu_pages * iommu_page_size;
>> +
>> +	b = find_reserved_binding(domain, aligned_base, binding_size);
>> +	if (b && (b->addr <= aligned_base) &&
>> +		(aligned_base + binding_size <=  b->addr + b->size))
>> +		iova = b->iova + offset + aligned_base - b->addr;
>> +unlock:
>> +	spin_unlock_irqrestore(&domain->reserved_lock, flags);
>> +	return iova;
>> +}
>> +
>> +int iommu_msi_mapping_translate_msg(struct irq_data *data, struct msi_msg *msg)
>> +{
> 
> I'm really not keen on passing a full irq_data to something that doesn't
> really care about it. What this really needs is the device that
> generates the MSIs, which makes a lot more sense (you get the device and
> the address from the msi_msg).
> 
> Or am I getting it wrong?

No I have no objection. I eventually decided to keep the irq_data*
parameter to be homegeneous with irq_chip_compose_msi_msg and I found
the function name understandable. However I also understand it looks
weird to get this irq-data incursion in this API

will change into iommu_msi_msg_pa_to_va, as you proposed.

Thank you for your time

Eric


> 
>> +	struct iommu_domain *d;
>> +	struct msi_desc *desc;
>> +	dma_addr_t iova;
>> +
>> +	desc = irq_data_get_msi_desc(data);
>> +	if (!desc)
>> +		return -EINVAL;
>> +
>> +	d = iommu_msi_mapping_desc_to_domain(desc);
>> +	if (!d)
>> +		return 0;
>> +
>> +	iova = iommu_find_reserved_iova(d, msg_to_phys_addr(msg),
>> +					sizeof(phys_addr_t));
>> +
>> +	if (iova == DMA_ERROR_CODE)
>> +		return -EINVAL;
>> +
>> +	msg->address_lo = lower_32_bits(iova);
>> +	msg->address_hi = upper_32_bits(iova);
>> +	return 0;
>> +}
>> +EXPORT_SYMBOL_GPL(iommu_msi_mapping_translate_msg);
>> diff --git a/include/linux/dma-reserved-iommu.h b/include/linux/dma-reserved-iommu.h
>> index 8373929..04e1912f 100644
>> --- a/include/linux/dma-reserved-iommu.h
>> +++ b/include/linux/dma-reserved-iommu.h
>> @@ -20,6 +20,8 @@
>>  
>>  struct iommu_domain;
>>  struct msi_desc;
>> +struct irq_data;
>> +struct msi_msg;
>>  
>>  #ifdef CONFIG_IOMMU_DMA_RESERVED
>>  
>> @@ -82,6 +84,25 @@ void iommu_put_reserved_iova(struct iommu_domain *domain, phys_addr_t addr);
>>   */
>>  struct iommu_domain *iommu_msi_mapping_desc_to_domain(struct msi_desc *desc);
>>  
>> +/**
>> + * iommu_msi_mapping_translate_msg: in case the MSI transaction is translated
>> + * by an IOMMU, the msg address must be an IOVA instead of a physical address.
>> + * This function overwrites the original MSI message containing the doorbell
>> + * physical address, result of the primary composition, with the doorbell IOVA.
>> + *
>> + * The doorbell physical address must be bound previously to an IOVA using
>> + * iommu_get_reserved_iova
>> + *
>> + * @data: irq data handle
>> + * @msg: original msi message containing the PA to be overwritten with
>> + * the IOVA
>> + *
>> + * return 0 if the MSI does not need to be mapped or when the PA/IOVA
>> + * were successfully swapped; return -EINVAL if the addresses need
>> + * to be swapped but not IOMMU binding is found
>> + */
>> +int iommu_msi_mapping_translate_msg(struct irq_data *data, struct msi_msg *msg);
>> +
>>  #else
>>  
>>  static inline int
>> @@ -111,5 +132,11 @@ iommu_msi_mapping_desc_to_domain(struct msi_desc *desc)
>>  	return NULL;
>>  }
>>  
>> +static inline int iommu_msi_mapping_translate_msg(struct irq_data *data,
>> +						  struct msi_msg *msg)
>> +{
>> +	return 0;
>> +}
>> +
>>  #endif	/* CONFIG_IOMMU_DMA_RESERVED */
>>  #endif	/* __DMA_RESERVED_IOMMU_H */
>>
> 
> Thanks,
> 
> 	M.
>