Re: [PATCH v2 1/2] iommu/dma: Implement dma_{map,unmap}_resource()
On Thu, Nov 10, 2016 at 02:30:04PM +, Robin Murphy wrote:
> On 10/11/16 12:24, Joerg Roedel wrote:
> > On Wed, Oct 26, 2016 at 06:43:56PM +0100, Robin Murphy wrote:
> >> With the new dma_{map,unmap}_resource() functions added to the DMA API
> >> for the benefit of cases like slave DMA, add suitable implementations to
> >> the arsenal of our generic layer. Since cache maintenance should not be
> >> a concern, these can both be standalone callback implementations without
> >> the need for arch code wrappers.
> >>
> >> CC: Joerg Roedel
> >> Signed-off-by: Robin Murphy
> >> ---
> >>
> >> v2: Use iommu_dma_unmap_page for symmetry, instead of being sneaky.
> >>
> >> drivers/iommu/dma-iommu.c | 13 +
> >> include/linux/dma-iommu.h | 4
> >> 2 files changed, 17 insertions(+)
> >>
> >> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> >> index c5ab8667e6f2..a2fd90a6a782 100644
> >> --- a/drivers/iommu/dma-iommu.c
> >> +++ b/drivers/iommu/dma-iommu.c
> >> @@ -624,6 +624,19 @@ void iommu_dma_unmap_sg(struct device *dev, struct
> >> scatterlist *sg, int nents,
> >>__iommu_dma_unmap(iommu_get_domain_for_dev(dev), sg_dma_address(sg));
> >> }
> >>
> >> +dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
> >> + size_t size, enum dma_data_direction dir, unsigned long attrs)
> >> +{
> >> + return iommu_dma_map_page(dev, phys_to_page(phys), offset_in_page(phys),
> >> + size, dma_direction_to_prot(dir, false) | IOMMU_MMIO);
> >> +}
> >
> > Isn't the whole point of map_resource that we can map regions which have
> > no 'struct page' associated? The use phys_to_page() will certainly not
> > do the right thing here.
>
> Perhaps it's a bit cheeky, but the struct page pointer is never
> dereferenced - the only thing iommu_dma_map_page() does with it is
> immediately convert it back again. Is there ever a case where
> page_to_phys(phys_to_page(phys)) != phys ?
Without SPARSEMEM_VMEMMAP or FLATMEM, it wouldn't work. For example,
__page_to_pfn() in the SPARSEMEM case, used by page_to_phys(), even
accesses the page structure (through page_to_section()).
If the page struct is not relevant to the iommu code in question, you
could factor it out into an __iommu_dma_map_pfn(). Or maybe move the
whole logic to iommu_dma_map_resource() and call it from
iommu_dma_map_page() with the page_to_phys(page) argument.
--
Catalin
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Re: [PATCH v2 1/2] iommu/dma: Implement dma_{map,unmap}_resource()
On 10/11/16 12:24, Joerg Roedel wrote:
> On Wed, Oct 26, 2016 at 06:43:56PM +0100, Robin Murphy wrote:
>> With the new dma_{map,unmap}_resource() functions added to the DMA API
>> for the benefit of cases like slave DMA, add suitable implementations to
>> the arsenal of our generic layer. Since cache maintenance should not be
>> a concern, these can both be standalone callback implementations without
>> the need for arch code wrappers.
>>
>> CC: Joerg Roedel
>> Signed-off-by: Robin Murphy
>> ---
>>
>> v2: Use iommu_dma_unmap_page for symmetry, instead of being sneaky.
>>
>> drivers/iommu/dma-iommu.c | 13 +
>> include/linux/dma-iommu.h | 4
>> 2 files changed, 17 insertions(+)
>>
>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
>> index c5ab8667e6f2..a2fd90a6a782 100644
>> --- a/drivers/iommu/dma-iommu.c
>> +++ b/drivers/iommu/dma-iommu.c
>> @@ -624,6 +624,19 @@ void iommu_dma_unmap_sg(struct device *dev, struct
>> scatterlist *sg, int nents,
>> __iommu_dma_unmap(iommu_get_domain_for_dev(dev), sg_dma_address(sg));
>> }
>>
>> +dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
>> +size_t size, enum dma_data_direction dir, unsigned long attrs)
>> +{
>> +return iommu_dma_map_page(dev, phys_to_page(phys), offset_in_page(phys),
>> +size, dma_direction_to_prot(dir, false) | IOMMU_MMIO);
>> +}
>
> Isn't the whole point of map_resource that we can map regions which have
> no 'struct page' associated? The use phys_to_page() will certainly not
> do the right thing here.
Perhaps it's a bit cheeky, but the struct page pointer is never
dereferenced - the only thing iommu_dma_map_page() does with it is
immediately convert it back again. Is there ever a case where
page_to_phys(phys_to_page(phys)) != phys ?
Robin.
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Re: [PATCH v2 1/2] iommu/dma: Implement dma_{map,unmap}_resource()
On Wed, Oct 26, 2016 at 06:43:56PM +0100, Robin Murphy wrote:
> With the new dma_{map,unmap}_resource() functions added to the DMA API
> for the benefit of cases like slave DMA, add suitable implementations to
> the arsenal of our generic layer. Since cache maintenance should not be
> a concern, these can both be standalone callback implementations without
> the need for arch code wrappers.
>
> CC: Joerg Roedel
> Signed-off-by: Robin Murphy
> ---
>
> v2: Use iommu_dma_unmap_page for symmetry, instead of being sneaky.
>
> drivers/iommu/dma-iommu.c | 13 +
> include/linux/dma-iommu.h | 4
> 2 files changed, 17 insertions(+)
>
> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
> index c5ab8667e6f2..a2fd90a6a782 100644
> --- a/drivers/iommu/dma-iommu.c
> +++ b/drivers/iommu/dma-iommu.c
> @@ -624,6 +624,19 @@ void iommu_dma_unmap_sg(struct device *dev, struct
> scatterlist *sg, int nents,
> __iommu_dma_unmap(iommu_get_domain_for_dev(dev), sg_dma_address(sg));
> }
>
> +dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
> + size_t size, enum dma_data_direction dir, unsigned long attrs)
> +{
> + return iommu_dma_map_page(dev, phys_to_page(phys), offset_in_page(phys),
> + size, dma_direction_to_prot(dir, false) | IOMMU_MMIO);
> +}
Isn't the whole point of map_resource that we can map regions which have
no 'struct page' associated? The use phys_to_page() will certainly not
do the right thing here.
Joerg
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[PATCH v2 1/2] iommu/dma: Implement dma_{map,unmap}_resource()
With the new dma_{map,unmap}_resource() functions added to the DMA API
for the benefit of cases like slave DMA, add suitable implementations to
the arsenal of our generic layer. Since cache maintenance should not be
a concern, these can both be standalone callback implementations without
the need for arch code wrappers.
CC: Joerg Roedel
Signed-off-by: Robin Murphy
---
v2: Use iommu_dma_unmap_page for symmetry, instead of being sneaky.
drivers/iommu/dma-iommu.c | 13 +
include/linux/dma-iommu.h | 4
2 files changed, 17 insertions(+)
diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index c5ab8667e6f2..a2fd90a6a782 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -624,6 +624,19 @@ void iommu_dma_unmap_sg(struct device *dev, struct
scatterlist *sg, int nents,
__iommu_dma_unmap(iommu_get_domain_for_dev(dev), sg_dma_address(sg));
}
+dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
+ size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+ return iommu_dma_map_page(dev, phys_to_page(phys), offset_in_page(phys),
+ size, dma_direction_to_prot(dir, false) | IOMMU_MMIO);
+}
+
+void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,
+ size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+ iommu_dma_unmap_page(dev, handle, size, dir, attrs);
+}
+
int iommu_dma_supported(struct device *dev, u64 mask)
{
/*
diff --git a/include/linux/dma-iommu.h b/include/linux/dma-iommu.h
index 32c589062bd9..7f7e9a7e3839 100644
--- a/include/linux/dma-iommu.h
+++ b/include/linux/dma-iommu.h
@@ -61,6 +61,10 @@ void iommu_dma_unmap_page(struct device *dev, dma_addr_t
handle, size_t size,
enum dma_data_direction dir, unsigned long attrs);
void iommu_dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nents,
enum dma_data_direction dir, unsigned long attrs);
+dma_addr_t iommu_dma_map_resource(struct device *dev, phys_addr_t phys,
+ size_t size, enum dma_data_direction dir, unsigned long attrs);
+void iommu_dma_unmap_resource(struct device *dev, dma_addr_t handle,
+ size_t size, enum dma_data_direction dir, unsigned long attrs);
int iommu_dma_supported(struct device *dev, u64 mask);
int iommu_dma_mapping_error(struct device *dev, dma_addr_t dma_addr);
--
1.9.1
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